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DICTIONARY 


SCIENTIFIC    TERMS. 


,  cy  C 


va~\fr«rfc 


RICHARD  D.  HOBLYN,  A.M.  Oxon. 

AUTHOR    OF 

«  A  DICTIONARY  OF  MEDICAL  TERMS," 

OF   "  MANUALS   OF    NATURAL    PHILOSOPHY,   OF   CHEMISTRV,   AND 

OF   THE   STEAM    ENGINE;" 

OF    "  FIRST    BOOKS    IN   SCIENCE,"    &C.   &C. 


NEW  YORK:  D.  APPLETON  AND  CO. 

PHILADELPHIA :  G.  S.  APPLETON. 

1850. 


£-  4  -T  ^  3 


o  a 


DICTIONARY 


OF 


SCIENTIFIC     TERMS. 


ABD 

A'BACUS  (a/3a£,  a  counter,  a  chess- 
board). An  ancient  instrument  for  aid- 
ing numerical  calculations.  The  Greek 
abacus  consisted  of  an  oblong  frame, 
having  wires  stretched  across  it,  carrying 
perforated  ivory  balls.  In  the  Roman 
abacus,  the  counters  were  slid  along 
grooves. 

ABBREVIATION  (abbrevio,  to  short- 
en). An  arithmetical  term,  denoting  the 
reduction  of  a  fraction  to  lower  terms,  by 
dividing  the  numerator  and  the  denomi- 
nator by  any  common  factors  which  they 
contain.  Thus  |^  divided  by  5  gives 
j^g;  and  this,  again  divided  by  3,  gives 
AS.  The  fraction  is  thus  reduced  or  ab- 
breviated, and,  when  it  can  no  more  be 
reduced,  it  is  said  to  be  in  its  lowest 
terms. 

ABDO'MEN  (abdo,  to  conceal).  The 
posterior  and  principal  cavity  containing 
the  bowels  and  many  other  viscera  of  the 
animal.  The  abdomen  is  distinct  from 
the  thorax  in  the  crustaceans,  the  spiders, 
and  the  insects. 

ABDOMINA'LES  (abdomen,  the  belly). 
An  order  of  malacopterygious  or  soft- 
f.nned  fishes,  which  have  their  ventral 
fins  placed  on  the  abdomen,  behind  the 
pectorals.  The  sub-families  of  the  order 
are  termed  by  Cuvier,  cyprinoides,  silu- 
ro'ides,  salmono'ides,  clupeoides,  and  lu- 
cioides,  from  the  respective  typ'cal  genera 
of  the  carps,  the  silures,  the  salmons,  the 
herrings,  and  the  pikes. 

ABDUCTOR  MUSCLE  (abduco,  to 
draw  from).  A  muscle  whose  office  is  to 
draw  one  part  of  the  body  from  another. 
Thus  the  rectus  externum  is  called  ab 
ductor  oculi,  fiom  the  action  of  this 
1 


ABE 

muscle  in  drawing  the  eye  away  from  the 
nose.     See  Adductor. 

ABE'RRANT  (aberro,  to  wander 
from).  A  term  applied  in  classification 
to  those  species  which  deviate  most  from 
the  type  of  their  natural  group. 

ABERRATION  Of  LIGHT  (aberro, 
to  wander  from).  An  astronomical  phe- 
nomenon consisting  in  an  alteration  in 
the  apparent  position  of  all  the  stars, 
owing  to  the  velocity  with  which  light 
moves,  and  to  the  motion  of  the  earth  in 
her  orbit,  in  a  direction  which  forms  a 
tangent  to  the  light  from  the  heavenly 
bodies.  In  consequence  of  the  aberra- 
tion resulting  from  the  combined  opera- 
tion of  these  two  velocities,  all  the  fixed 
stars  appear  to  us  to  be  rather  more  back- 
ward than  they  really  are  in  the  direction 
of  the  earth's  annual  motion.  Aberra- 
tion is  never  so  much  as  21";  in  other 
words,  the  apparent  place  of  the  star 
differs  from  its  real  place  less  than  the 
ninetieth  part  of  the  apparent  diameter 
of  the  sun. 

1.  Aberration,  Spherical.  A  term  em- 
ployed in  Optics  to  denote  the  deviation 
of  the  rays  of  light  from  the  true  focus  of  a 
curved  lens  or  mirror  ;  in  consequence  of 
which,  instead  of  concentering  in  a  single 
point,  they  are  spread  over  a  certain  sur- 
face, forming  a  confused  image  of  the 
object.  These  aberrations  proceed,  1,  from 
the  form  of  curvature  of  the  lens  or  mir- 
ror, and  2,  from  the  different  refrangibility 
of  the  rays  of  light.     See  Refrangibility. 

2.  Aberration,  Chromatic.  A  term  em- 
ployed in  Optics  to  denote  the  imperfec- 
tion arising  from  the  unequal  refrangibi- 
lity of  the  rays  composing  white  light, 

B 


A  BR 


ABS 


in  consequence  of  which  the  image  of  the 
object,  viewed  through  a  lens,  will  be 
surrounded  by  prismatic  colours.  Sphe- 
rical aberration  produces  distortion,  chro- 
matic aberration  produces  false  colour,  of 
the  object. 

3.  Aberration,  circle  of.  The  circle  of 
coloured  light  observed,  in  experiments 
with  convex  lenses,  between  the  point 
where  theviolet  or  most  refrangible,  and 
the  point  where  the  red  or  least  refran- 
gible rays  meet. 

ABIETTN^E  {abies,  a  fir-tree).  A  sec- 
tion of  the  Coniferse,  or  Fir-tree  tribe  of 
plants,  comprising  the  Fir,  the  Pine,  the 
Araucaria,  the  Dammara,  and  the  Cun- 
ninghamia. 

A'BLATIVE  CASE  (ab,  from,  fero, 
latus,  to  take).  Literally,  the  taking 
away  case  ;  a  case  belonging  to  the  Latin 
language,  and  known  by  prepositions, 
expressed  or  understood.  It  is  repre- 
sented in  the  English  language  by  the 
preposition  from.     See  Case. 

ABNO'RMAL  {ab,  from,  norma,  arule). 
Irregular ;  that  which  deviates  from  the 
usual  order.  The  term  anormal  is  also 
employed  to  denote  any  thing  that  is 
without  rule  or  order.  The  terms  are 
nearly  synonymous. 

ABO'RTIVE  {aborior,  to  be  born  before 
the  time).  A  term  applied  in  botany  to 
any  part  of  a  plant  which  does  not  ac- 
quire its  normal  development:  stamens 
which  have  no  anthers,  and  seeds  which 
have  no  embryos,  are  said  to  be  abortive. 
But  abortion  may  be  constant :  the  ova- 
rium of  the  Cocoa  palm  is  three-celled  ; 
the  fruit  has  only  one  cell,  the  other  two 
becoming  constantly  abortive. 

ABR  A'NCHIA  («  priv.,  /3Pa7X"»»  gills). 
The  third  order  of  the  Anellida  of  Cuvier, 
comprising  animals  which  have  no  gills, 
or  apparent  external  organs  of  respira- 
tion, but  respire  by  the  entire  surface  of 
the  skin,  or  by  internal  cavities.  They 
are  distinguished  into  the  setigerous,  or 
worms,  and  the  non-setigerous,  or  leeches. 
The  term  Abranchia  has  been  also  ap- 
plied to  an  order  of  amphibious  animals, 
which  are  not  known  to  undergo  meta- 
morphosis, but  breathe  by  lungs  during 
the  whole  period  of  life.  The  order 
comprises  only  two  genera,  viz.  the  me- 
nopoma  and  the  amphiuma  of  North 
America. 

A'BRAZITE.  A  mineral  found  in  the 
cavities  of  volcanic  rocks,  with  calcareous 
spar,  at  Capo  di  Bove,  near  Rome.  It 
occurs  in  semi-globular  masses,  and  in 
octohedral  crystals  with  a  square  base. 
2 


It  is  also  termed  zeagonite  and  gismon- 
dine. 

ABRU'PTLY  PINNATE.  A  pinnate 
leaf  is  thus  named  in  botany,  when  its 
petiole  has  no  terminal  leaflet  or  tendril, 
as  in  Orobus  tuberosus. 

ABSCI'SSA  (abscindo,  to  cut  off).  Linea 
abscissa.  A  term  employed  in  Conic  Sec- 
tions, to  denote  that  portion  of  the  major 
axis  of  an  ellipse  which  is  cut  off  by  an 
ordinate.  The  term  is  equally  applicable 
to  the  parabola  and  to  the  hyperbola.  See 
Ordinate  and  Co-ordinaip. 

A'BSOLUTE  and  RE'LATIVE.  In 
logic,  a  noun  which  denotes  an  object 
considered  as  a  whole,  and  without  re- 
ference to  any  thing  of  which  it  is  a  part, 
or  to  any  other  part  distinguished  from 
it,  is  called  absolute.  When,  on  the  other 
hand,  an  object  is  considered  as  a  part  of 
a  whole,  viewed  in  reference  to  the 
whole,  or  to  another  part  of  a  more  com- 
plex object  of  thought,  the  noun  express- 
ing this  view  is  called  relative.  Thus, 
"  father  "  and  "  son  "  are  relatives,  being 
regarded,  each  as  a  part  of  the  complex 
object,  father-and  son  ;  whereas  the 
same  object  designated  absolutely  would 
be  termed  a  man,  living  being,  &c. 

ABSORPTION  (absorbeo,  to  suck  up). 
A  function  in  physiology,  by  which  the 
materials  of  growth  are  absorbed  and  con- 
veyed to  the  organs  of  the  body,  and  by 
which  the  decayed  and  useless  parts  are 
absorbed  and  removed  from  the  system. 

1.  Interstitial  Absorption.  The  func- 
tion by  which  the  particles  of  the  tissue 
which  fill  the  meshes  of  the  capillary  net- 
work are  removed,  as  in  the  atrophy  of 
the  tail  of  the  tadpole,  and  of  the  pupil- 
lary membrane  in  the  foetus,  and  in  the 
development  of  cells  in  bones. 

2.  Absorption,  in  Chemistry.  This  term 
denotes  the  passage  of  a  gas  or  vapour 
into  a  liquid  or  solid  substance  ;  or  that  of 
a  liquid  into  the  pores  of  a  solid.  Thus, 
water  absorbs  carbonic  acid  gas,  lime 
absorbs  water,  &c. 

ABSTRACT  and  CONCRETE.  1.  In 
logic,  when  a  notion  derived  from  the 
view  taken  of  any  object,  is  expressed 
with  a  reference  to,  or  as  taken  in  con- 
junction with,  the  object  which  furnished 
the  notion,  it  is  expressed  by  a  concrete 
term,  as  "foolish"  or  "fool;"  when 
without  any  such  reference,  by  an  abs- 
tract term,  as  "  folly."  2.  In  arithmetic, 
when  numbers  are  used  with  reference 
to  the  things  numbered,  as  3  shillings,  4 
acres,  5  kingdoms,  they  are  said  to  be  con- 
crete numbers ;  when  used  without  such 


Q>^ 


jfbMA 


AC  A 

reference,  merely  to  indicate  a  certain 
number  of  units  of  the  same  kind,  as 
when  we  simply  say  3,  4,  5,  they  are 
called  abstract  numbers.  The  multipli- 
cation table  is  a  series  of  abstract  num- 
bers.    See  Abstraction. 

ABSTRACTION  {abstraho,  to  draw 
off).  The  operation  of  the  mind  by 
which  we  draw  off,  and  contemplate  sepa- 
rately, some  portion  or  property  of  an 
object,  as  the  scent  of  a  rose,  disregard- 
ing all  else  that  belongs  to  it.  The  ope- 
ration, therefore,  strictly  speaking,  may 
be  limited  to  the  contemplation  of  a  single 
object.  But  the  term  is  usually  employed 
in  a  wider  sense:  in  contemplating  several 
objects  which  agree  in  certain  points,  we 
abstract  the  circumstances  of  agreement, 
disregarding  the  differences,  and  give  to 
all  and  each  of  these  circumstances  a 
common  name,  expressive  of  this  agree- 
ment ;  we  are  then,  properly,  said  to 
generalize.  Abstraction,  therefore,  does 
not  necessarily  imply  generalization, 
though  generalization  implies  abstrac- 
tion. 

ABSU'RDUM,  REDUCTIO  AD.  A 
form  of  argument,  frequently  employed 
in  geometrical  reasoning,  by  which,  in- 
stead of  proving  the  thing  asserted,  the 
absurdity  is  shown  of  every  thing  which 
contradicts  that  assertion.  For  it  follows 
that,  if  every  thing  which  contradicts  a 
proposition  be  false,  the  proposition  itself 
must  be  true. 

ABU'NDANT  NUMBER.  Any  num- 
ber which  is  less  than  the  sum  of  its  di- 
visors, as  12,  which  is  less  than  the  sum 
of  /  2,  3,  4,  and  6,  all  of  which  are  its 
divisors,  and  their  sum  is  16.  A  deficient 
number  is  that  which  is  greater  than  the 
sum  of  its  divisors ;  a  perfect  number, 
that  which  is^equal  to  the  sum  of  its  di- 
visors^*-£ 

ACALE'PHjE  (ixaX^rj,  a  nettle).  Sea- 
nettles  ;  a  class  of  gelatinous  zoophytes, 
found  in  the  water  of  the  ocean,  and  so 
named  from  the  stinging  sensation  which 
many  of  them  produce  when  touched. 
To  this  class  belong  the  sea-jelly,  sea- 
nettle,  Portuguese  man-of-war,  &c.  By 
the  old  naturalists  they  were  known  by  the 
title  of  urticcB  marines.  See  Malactinia. 
ACA'NTH  A  i'dKavda,  a  thorn).  A  spine, 
or  prickle  ot  a  plant.  A  prickly  tin  of  a 
fish.     A  spinous  process  of  a  vertebra. 

ACANTHA'CEjE.  The  Justicia  tribe 
of  Dicotyledonous  plants,  named  from 
the  genus  Acanthus.  Herbaceous  plants 
or  shrubs,  with  leaves  opposite ;  corolla 
gamopetalous  ;  stamens  mostly  2  ;  capsule 
3 


ACC 

2-celled,  bursting  elastically  with  2  valves; 
seeds  usually  hooked,  exalbumiuous. 

ACANTHA'LES.  An  alliance  of  Dico- 
tyledonous plants.  Flowers  unsymme- 
trical,  usually  didynamous.  Seeds  ad- 
hering to  hard  hook  like  processes  of  the 
placenta.  Albumen  0.  Calyx  4-5-leaved, 
remarkably  imbricated,  as  if  in  more 
whorls  than  one ;  often  enveloped  in 
large  bracts. 

ACA'NTHOCE'PHALA  {'dKavOa,  a 
spine,  KetpaXij,  the  head).  Hooked 
worms;  an  order  of  the  Entozoa,  which 
have  an  elongated  cylindrical  body,  with 
the  anterior  part  closely  covered  with 
small  sharp  spines,  and  the  oral  aper- 
ture leading  to  a  ramified  alimentary 
canal. 

ACA'NTHOPTERY'GII  (SKavfla,  a 
thorn,  7TT€pvytov,  a  fin).  Spinous-finned 
fishes,  or  fishes  whose  dorsal  fins  are  bony 
and  prickly ;  one  of  the  three  primary 
grand  divisions,  or  natural  orders  of 
fishes,  established  by  Cuvier.  The  order 
comprises  fifteen  families. 

ACA'NTICONE.  A  sub-species  of 
prismatoi'dal  augite,  occurring  in  primi- 
tive beds  and  veins,  in  Norway  and  other 
parts.  It  is  of  a  pistachio-green  colour, 
and  is  known  by  the  names  pistacite  and 
epidote. 

A'CARID^E.  A  family  of  the  Arach- 
nida,  belonging  to  the  order  Tracheata, 
and  named  from  the  typical  genus  acarus, 
to  which  the  mite,  the  tick,  the  water- 
mite,  and  the  flesh- worm  belong.  The 
last  of  these  is  distinguished  from  the 
rest  by  the  presence  of  only  six  feet. 

ACAULE'SCENT  (a,  priv.,  Kav\6t,  a 
stalk).  Stemless ;  a  term  applied  to  a 
plant  in  which  the  stem  is  apparently 
absent,  and  the  leaves  seem  to  rise  from 
the  root,  as  in  Cnicus  acaulis.  As,  how- 
ever, according  to  the  theory  of  vegetable 
development,  a  stem  is  assumed  to  exist, 
the  term  subcaulescent  would  be  prefer- 
able. 

ACCELERATION  (accelero,  to  has- 
ten). The  increase  of  the  motion  of 
moving  bodies.  Thus,  a  stone,  falling  to 
the  earth,  moves  faster  and  faster  as  it 
descends  ;  its  motion  is  therefore  said 
to  be  continually  accelerated ;  in  other 
words,  its  velocity  continually  increases. 
1.  Acceleration  of  the  fixed  stars.  The 
time  by  which  the  stars,  in  their  diurnal 
revolution,  anticipate  the  mean  diurnal 
revolution  of  the  sun ;  which  is  three 
minutes  and  fifty-six  seconds.  Thus,  a 
star,  which  to-day  passes  the  meridian  at 
twelve  o'clock,  mean  time,  will  pass  the 
B2 


A  C  C 


ACE 


meridian  to-morrow  three  minutes  and 
fifty-six  seconds  before  twelve  o'clock. 

2.  Acceleration  of  the  planets.  The 
motion  of  the  planets  varies  in  different, 
parts  of  their  orbits,  according  as  they 
are  at  a  greater  or  less  distance  from  the 
sun.  From  their  aphelion  to  their  peri- 
helion their  motion  is  accelerate, i ;  from 
their  perihelion  to  their  aphelion  it  is 
retarded.  The  average  of  these  motions 
through  the  whole  orbit  (the  space  di- 
vided by  the  time)  is  called  the  mean 
motion.  Hence,  the  acceleration  of  a 
planet  is  the  excess  of  its  real  diur- 
nal motion  over  its  mean  diurnal  mo- 
tion. 

3.  Secular  acceleration  of  the  moon's 
mean  motion.  An  increase  in  the  velo- 
city of  the  moon's  mean  motion  around 
the  earth.  It  amounts  to  about  11  se- 
conds per  century — a  quantity  small  in 
itself,  but  becoming  considerable  by  its 
accumulation  during  a  succession  of 
ages. 

A'CCENT  {aecentus,  from  accino,  to 
sing  in  concert).  A  peculiar  stress  or 
elevation  of  the  voice,  which  distin- 
guishes one  syllable  in  every  word  which 
consists  of  more  than  one  syllable.  The 
syllable  so  distinguished  is  said  to  have 
the  acute  accent,  which  is  marked  thus 
(') ;  ths  grave  ( ),  which  is  seldom  marked, 
is  supposed  to  be  placed  over  those  syl- 
lables which  are  pronounced  without  the 
elevation  of  the  voice ;  the  circumflex 
C  or  ")  is  supposed  to  be  formed  by  a 
combination  of  the  acute  and  the  grave, 
and  hence  is  usually  placed  over  con- 
tracted syllables.  In  modern  languages 
the  accent,  when  it  falls  upon  a  short  syl- 
lable, has,  in  most  cases,  the  same  effect 
as  if  it  were  long ;  but  in  the  ancient 
languages,  accent  and  quantity  were  dis- 
tinguished from  each  other. 

ACCENTS,  MATHEMATICAL.  Dif- 
ferent magnitudes  of  the  same  kind,  or 
magnitudes  placed  in  similar  positions, 
are  denoted,  in  algebraical  calculations, 
by  the  use  of  the  same  letter  distin- 
guished by  accents.  The  accented  letter 
a'  is  read  a  accented  or  a  dashed;  a"  is 
read  a  twice  accented,  or  a  twice  dashed, 
or,  more  commonly,  a  two  dash.  When 
accents  are  inconveniently  numerous, 
Roman  figures  are  employed :  thus  aiv  is 
used  instead  of  a"".  The  accented  letter 
is  the  metaphor  of  algebra. 

A'CCESSORY  VALVES  (accedo,  to  be 
added).  Small  additional  valves  placed 
near  the  um bones  or  bosses  of  the  genus 
pholas  among  shells,  and  on  the  edges  of 


the  pedunculated  barnacles,  among  an- 
nulose  animals. 

A'CCIDENT  {accido,  to  happen  to). 
This  term,  in  its  widest  technical  sense, 
denotes  any  thing  which  can  be  attri- 
buted to  an  object,  and  can  only  be  con- 
ceived as  belonging  to  some  substance, 
in  which  sense  it  is  opposed  to  "sub- 
stance." In  its  more  restricted  and  logi- 
cal sense,  it  is  a  predicable,  which  may  be 
absent  or  present,  the  essence  of  the 
species  remaining  the  same.  An  acci- 
dent is  called  separable,  when  it  may  be 
separated  from  the  individual ;  insepa- 
rable, when  it  cannot  be  separated  from 
the  individual :  the  word  "  individual " 
is  here  emphatic,  because  every  accident 
must  be  separable  from  the  species,  else 
it  would  be  a  property. 

ACCFPITRES  {accipiter,  a  hawk). 
Raptores.  Rapacious  birds;  birds  of 
prey ;  known  by  their  hooked  beak  and 
talons.  They  are  distinguished  into  the 
diurnal  and  the  nocturnal ;  the  former 
comprising  the  falcons,  eagles,  vultures, 
&c. ;  the  latter  the  owls. 

A'CCLIMA'TION.  Naturalization  to 
a  foreign  or  unusual  climate ;  a  term  ap- 
plied to  plants  and  animals. 

ACCRETION  (accresco,  to  grow  to). 
The  addition  of  new  parts,  as  in  the 
formation  of  a  crystal  by  the  position  of 
new  parts  around  a  central  nucleus.  The 
organic  and  inorganic  kingdoms  are  dis- 
tinguished by  their  mode  of  increase; 
the  former  increasing  by  intussusception 
and  alimentation,  the  latter  by  accretion 
without  alimentation. 

ACCU'MBENT  (accumbo,  to  lie  down). 
Lying  against  any  thing,  as  the  edges  of 
the  cotyledons  against  the  radicle  in  some 
cruciferous  plants.     See  Incumbent. 

ACCUSATIVE  CASE  (accuso,  to  ac- 
cuse). Literally,  the  aiming  at  case ;  a 
case  belonging  to  the  Latin  language,  and 
denoting,  originally,  the  object  to  which 
any  motion  or  action  is  directed  ;  it  was, 
afterwards,  employed  to  distinguish  the 
object  of  any  action  or  feeling.  It  cor- 
responds with  the  objective  case,  or  the 
object,  of  the  English  Grammar.  See 
Case. 

-ACEOUS.  Terminations  in  -aceous 
denote  a  resemblance  to  a  substance,  as 
membranaceous,  resembling  membrane; 
whereas  terminations  in  -ous  denote  the 
substance  itself,  as  membranous,  belong- 
ing to  membrane. 

ACE'PHALA  (a,  priv.,  Ke<pa\t],  the 
head).  Headless  animals;  a  class  of  the 
Mollusca,  which  have  no  head,  but  simply 


ACE 


ACH 


a  pharynx,  or  beginning  of  the  oesophagus 
without  jaws,  tongue,  or  mouth  properly 
so  called,  as  in  the  oyster.  According  to 
Cuvier,  this  class  of  molluscous  animals 
comprehends  many  genera  with  bivalve 
shells,  or  acephala  testacea ;  and  a  few 
which  are  devoid  of  shells,  or  acephala 
nuda. 

ACEPHALO'PHORA  (a,  priv.,  «e- 
<pa\r],  the  head,  0<?pa>,  to  bear).  A  term 
applied  by  Blainville  to  a  class  of  mollus- 
cous animals  corresponding  with  the 
acephala  and  the  brachiopoda  of  Cuvier. 

ACERA'CEiE.  The  Sycamore  tribe  of 
Dicotyledonous  plants,  named  from  the 
genus  Acer.  Trees,  with  leaves  opposite ; 
petals  generally  5  ;  stamens  usually  8,  in- 
serted with  the  petals  on  a  hypogynous 
disk ;  fruit  dicarpellary,  samaroid  ;  seeds 
exalbuminous. 

ACERA'LES.  An  alliance  of  Dicoty- 
ledonous plants.  Stamens  definite  in 
number.  Flowers  usually  un symmetri- 
cal in  their  parts,  or,  if  symmetrical, 
more  or  less  irregular ;  in  the  majority, 
small,  and  disposed  in  a  compound  inflo- 
rescence. 

A'CERIC  ACID.  A  peculiar  acid  said 
to  exist  in  the  sap  of  the  acer,  or  maple 
tree. 

A'CEROSE  {acerosus,  chaffy).  Sharp- 
pointed  ;  tapering  to  a  fine  point,  as  the 
leaves  of  juniper. 

ACESCENT  (acesco,  to  become  sour). 
A  term  applied  to  substances  which  be- 
come sour  spontaneously,  as  vegetable 
and  animal  juices,  or  infusions. 

ACETABULUM  {acetum,  vinegar).  A 
vinegar-cruet ;  and  hence  a  cup-like  ca- 
vity, as  the  suckers  on  the  arms  of  the 
cuttle-fish,  the  cavity  of  the  hip-joint, 
the  socket  on  the  trunk  of  insects  which 
receives  the  leg.  Also,  a  Roman  mea- 
sure containing  two  ounces  and  a  half. 

ACE'TAL.  A  compound  of  aldehyde 
with  ether,  formed  by  the  action  of  plati- 
num black  on  the  vapour  of  alcohol  with 
the  presence  of  oxygen.  The  term  is 
derived  from  acetum,  vinegar,  and  the 
first  syllable  of  alcohol. 

A'CETATE  {acetum,  vinegar).  A  salt 
formed  by  the  union  of  acetic  acid  with 
an  alkaline,  an  earthy  or  a  metallic 
base. 

ACE'TIC  ACID  {acetum,  vinegar).  The 
pure  acid  of  vinegar.  It  occurs,  ready 
formed,  in  several  products  of  the  vege- 
table kingdom,  and  is  generated  during 
the  spontaneous  fermentation  of  many 
vegetable  and  animal  juices.  By  real 
acetic  acid  is  meant  such  an  acid  as 
5 


occurs  in  a  dry  acetate:  it  cannot  exist  in 
an  uncombined  state. 

ACETO'METER  {acetum,  vinegar, 
/ierpoj/,  a  measure).  An  instrument  for 
ascertaining  the  strength  of  vinegars. 
It  consists  of  a  globe  of  glass  about  three 
inches  in  diameter,  having  a  little  ballast 
ball  drawn  out  beneath,  and  a  stem  above 
of  about  three  inches  long,  containing  a 
slip  of  paper,  with  a  transverse  line  in 
the  middle,  and  surmounted  with  a  little 
cup  for  receiving  weights  or  poises. 

ACETONE.  The  new  chemical  name 
for  pyro-acetic  spirit;  a  limpid  colourless 
liquid,  prepared  by  distilling  a  mixture 
of  two  parts  of  crystallized  acetate  of  lead 
and  one  part  of  quicklime  in  a  salt-glaze 
jar.  The  names  of  such  pyrogen  bodies 
terminate  in  one,  as  contain  one  atom  of 
oxygen  and  are  neutral. 

ACETYL.  A  hypothetical  radical, 
pervading  a  series  of  compounds,  includ- 
ing acetic  acid,  and  prepared  by  abstract- 
ing two  atoms  of  oxygen  from  ethyl. 
The  term  is  derived  from  acetum,  vine- 
gar, and  vXrj,  matter. 

ACHjE'NIUM  (a,  priv.,  xa/vw,  to  open). 
An  indehiscent  fruit ;  one-celled,  one- 
seeded,  superior,  hard,  and  dry,  with  the 
integuments  of  the  seed  distinct  from  it. 
It  occurs  in  the  Labiatae  and  the  Bora- 
gin  eae. 

ACHATINjE.  Spiral  snails;  a  sub- 
family of  the  Helicidce,  named  from  the 
genus  Achatina :  the  spire  of  their  shells 
is  elongated  and  conical. 

ACHE'RNAR.  A  star  of  the  first  mag- 
nitude in  the  southern  constellation  Eri- 
danus. 

ACHE'TIDjE.  A  group  of  Orthopte- 
rous  insects,  belonging  to  the  family  Sal- 
tatoria,  and  including  the  species  known 
as  crickets.  Many  of  them  burrow  in  the 
ground,  and  most  of  them,  like  the  house- 
cricket,  are  nocturnal.  Few  have  any 
power  of  active  flight. 

A'CHIRITE.  Emerald  malachite;  a 
mineral  consisting  of  oxide  of  copper, 
carbonate  of  lime,  silica,  and  water. 

ACHLAMY'DEOUS  (a,  priv.,  x^pvn, 
a  cloak).  The  general  name  of  all  those 
plants  from  which  the  floral  envelopes — 
the  calyx  and  the  corolla — are  both  ab- 
sent. 

A'CHMIT.  A  mineral,  supposed  to  be 
a  bisilicate  of  soda,  combined  with  a 
bisilicate  of  iron. 

ACHROMATIC  (a,  priv.,  xpwixa,  co- 
lour).   An  optical  term  signifying  colour- 
less as   applied  to  a  lens,  in  which  the 
primary  colours  which  usually  accompany 
B3 


AC1 


ACO 


the  transmission  of  the  image  of  any  ob- 
ject through  such  a  medium,  are  de- 
stroyed. The  colours  which  appear  round 
the  edges  of  an  object,  when  viewed 
through  an  ordinary  telescope,  are  pro- 
duced by  the  different  ref'rangibility  of 
the  rays  of  light ;  and  telescopes  which 
are  constructed  so  as  to  counteract  or 
prevent  this  aberration,  are  termed  achro- 
matic. 

ACI'CULAR  (acicula,  a  little  needle). 
A  term  applied,  in  crystallography,  to 
needle  shaped  crystals  ;  and,  in  botany,  to 
the  leaves  of  plants  which  are  long,  stiff, 
and  pointed,  like  a  needle  ;  or  to  surfaces 
which  are  marked  with  fine  needle-like 
streaks. 

A'CIDS.  A  class  of  compounds  which 
generally  possess  a  sharp  and  sour  taste, 
and  are  often  highly  corrosive ;  they  red- 
den the  infusions  of  blue  vegetable  co- 
lours, and  combine  with  the  alkalies, 
earths,  and  metallic  oxides,  forming 
compounds  in  which  the  characters  of 
the  constituents  are  entirely  destroyed, 
and  new  characters  produced  differing  in 
every  respect  from  those  previously  ex- 
isting.    See  Alkalies. 

1.  Oxygen  Acids.  When  the  same  ele- 
ment forms  two  acid  compounds  with 
oxygen,  the  name  of  that  which  contains 
the  greater  proportion  of  oxygen  is  made 
to  terminate  in  ic,  the  other  in  ous,  as  in 
sulphuric  and  sulphurous  acids.  A  lower 
degree  of  oxidation  is  expressed  by  pre- 
fixing the  Greek  preposition  hypo  (biro, 
under),  as  in  hypo-sulphurous  acid;  while 
another  new  compound,  intermediate  be- 
tween the  sulphurous  and  sulphuric  acids, 
was  named  hypo-sulphuric  acid.  On  the 
same  principle,  the  highest  degree  of  oxi- 
dation is  expressed  by  prefixing  the 
Greek  preposition  hyper  {vnep,  over),  as 
in  hyper-chloric  acid.  This  nomenclature 
has  been  adopted  for  all  analogous  acids. 

2.  Hydrogen  Acids.  These  are  acid 
compounds  of  certain  substances,  as 
chlorine,  sulphur,  and  cyanogen,  with 
hydrogen,  and  they  are  hence  called  hy- 
dracids.  In  these  compounds  the  names 
of  both  constituents  appear,  as  in  the 
terms  hydrochloric,  hydrosulphuric,  and 
hydrocyanic  acid.  Thenard  has  lately 
altered  these  names  to  chlorhydric,  sul- 
phohydric,  and  cyanhydric  acid,  which 
are  better  terms. 

3.  Sulphur  acids.  In  this  class  of  acids 
sulphur  is  united  with  the  other  element 
in  the  place  of  oxygen.  The  names  of 
the  corresponding  oxygen  acids  are  some- 
times applied  to  these  with  the  prefix 
6 


sulpho,  as  sulpho-arsenious  and  sulpho- 
arsenic  acids,  which  resemble  arsenious 
and  arsenic  acids  respectively  in  com- 
position, but  contain  sulphur  instead  of 
oxygen. 

ACIDIFI'ABLE.  Capable  of  being 
converted  into  an  acid  by  an  acidifying 
principle.  Substances  possessing  this 
property  are  called  radicals,  or  acidifiable 
bases. 

ACIDIFYING  PRINCIPLE.  That 
principle  which  is  capable  of  converting 
a  substance  into  an  acid. 

ACIDPMETRY  {acidum,  an  acid,  Me- 
rpov,  a  measure).  The  process  of  mea- 
suring the  strength  of  an  acid,  by  satura- 
ting a  given  weight  of  it  with  an  alkaline 
base  :  the  quantity  of  the  base  required 
for  saturation  is  a  measure  of  the  strength 
of  the  acid. 

ACIDULOUS.  Slightly  acid;  a  term 
frequently  applied  to  mineral  waters 
which  contain  carbonic  acid ;  and,  in 
chemical  language,  to  those  salts  in  which 
the  base  is  combined  with  such  an  excess 
of  acid,  that  they  distinctly  exhibit  acid 
properties,  as  the  super-tartrate  of  po- 
tassa. 

ACINA'CIFORM  (acinaces,  a  scimitar, 
forma,  likeness).  Scimitar-shaped ;  plane 
on  the  sides,  with  one  border  thick,  the 
other  thin,  as  the  succulent  leaves  of  the 
Mesembryanthemum  acinaciforme. 

A'CINI  (plural  of  acinus,  a  grape- 
stone).  A  term  applied  by  some  carpo- 
logists  to  the  minute  component  parts  of 
the  raspberry :  incorrectly,  however  ;  for 
these  are  drupes.  The  term  is  also  ap- 
plied to  the  secerning  parts  of  glands, 
when  they  are  suspended  like  grains  or 
small  berries  from  a  slender  stem. 

ACLI'NIC  LINE  (a,  priv.,  kXIvco,  to 
incline).  The  name  given  by  Professor 
August  to  an  irregular  curve  in  the 
neighbourhood  of  the  terrestrial  equator, 
where  a  needle  balances  itself  perfectly 
horizontally.  It  is  sometimes  called  the 
magnetic  equator. 

ACORA'CEiE.  An  order  of  Mono- 
cotyledonous  plants,  named  from  the 
genus  Acorus.  Rhizoma  jointed  ;  leaves 
ensiform ;  flowers  hermaphrodite,  sur- 
rounded with  scales  ;  spathe  leaf-like  ; 
stamens  with  2-celled  anthers,  turned  in- 
wards ;  ovaries  distinct ;  fruit  finally 
juiceless ;  seeds  albuminous. 

A'COTYLE'DON  (a,  priv.,  kotvXvSwv, 
a  seed-lobe).  A  plant  whose  embryo 
has  no  cotyledons,  or  seed-lobes.  But 
the  acotyledonous  embryo  is  not  exactly, 
as  its  name  seems  to  indicate,  an  embryo 


ACT 


ACU 


without  cotyledons;  for,  in  that  case, 
cuscuta  would  be  acotyledonous.  On  the 
contrary,  it  is  an  embryo  which  does  not 
germinate  from  two  fixed  invariable 
points,  namely,  the  plumule  and  the  ra- 
dicle, but  indifferently  from  any  point  of 
the  surface,  as  in  some  Araceae,  and  in 
all  flowerless  plants. 

ACOU'STICS  (ukovco,  to  hear).  The 
science  of  sound ;  the  laws  which  regu- 
late the  vibrations  of  air,  or  of  other 
media,  in  their  relation  to  the  organ  of 
hearing. 

A'CRITA  (a/cptTor,  indistinct).  A  pri- 
mary division  of  the  Animal  Kingdom, 
composed  of  the  lowest  classes  of  the 
radiate  animals,  and  characterized  by  an 
indistinct,  diffused,  or  molecular  condi- 
tion of  the  nervous  system,  and  by  the 
absence  of  distinct  parietes  to  the  ali- 
mentary canal.  To  this  division  belong 
the  medusa,  the  polype,  &c.  These  are 
the  cryptoneura  of  Rudolphi,  the  protozoa 
and  oozoa  of  others.    See  Nematoneura. 

A'CROGEN  (aKpov,  extreme,  yeipo/nat, 
to  grow).  Point-grower ;  the  classical  name 
of  a  plant  which  grows  only  at  its  point, 
or  upper  extremity,  as  a  fern  tree,  and  is 
thus  distinguished  from  an  endogen  on 
the  one  hand,  and  an  exogen  on  the  other. 

ACRO'LEINE  (ckpor,  extreme,  e\aiov, 
oil).  A  substance  of  a  very  pungent 
odour  given  off  by  oils  and  fats  when 
boiling  at  a  high  temperature,  and  pro- 
duced in  large  quantity  by  the  distillation 
of  pure  glycerin. 

ACRO'NYCHAL  (cUpoc,  extreme,  ™f, 
night).  A  Greek  term  denoting  the  ex- 
tremities, or  the  beginning  and  the  end, 
of  the  night.  Hence,  a  star  is  said  to  be 
acronychal,  or  to  rise  acronychally,  when 
it  rises  at  sunset,  and  consequently  sets 
at  sunrise. 

A'CROSPIRE  (a«poc,  extreme,  a-irelpa, 
a  spire).  That  part  of  a  germinating  em- 
bryo which  botanists  call  the  plumula, 
and  which  bears  the  cotyledons.  It  has 
a  curved  form,  and  makes  its  appearance 
at  the  extremity  of  the  seed. 
'  ACTERAPMIN.  A  star  of  the  third 
magnitude,  in  the  left  shoulder  of  Ce- 
pheus,  marked  a. 

ACTINE'NCHYMA  (cue™,  a  ray  of 
light,  f7X"Ma>  an  infusion).  A  term  ap- 
plied by  some  botanical  writers  to  the 
stellate,  or  star-shaped  variety  of  sphe- 
roidal cellular  tissue. 

ACTPNIA  [iatrhf,  a  ray  of  light).    A 
form  of  polype,  in  which  the  mouth  oc- 
cupies the  centre  of  the  upper  surface, 
and  is  surrounded  by  tentacuia,  which 
7 


radiate  from  the  centre,  like  the  petals  of 
a  flower.  Hence,  the  genus  has  acquired 
the  names  of  animal  flowers,  sea  ane- 
mones, &c.  From  the  fihrous  character 
which  the  substance  of  their  bodies  as- 
sumes, they  have  been  named  by  zooJo- 
gists  fleshy  polyps. 

ACTINO'CEROS  (uht'iv,  a  ray,  nepat, 
a  horn).  A  generic  term,  signifying  the 
radiated  disposition  of  the  horns  or 
feelers  of  animals. 

ACTPNOLITE  {dvrlv,  a  ray  of  light, 
\i9ov,  a  stone).  A  green-coloured  mine- 
ral, forming  a  variety  of  hornblende,  and 
usually  occurring  in  fascicular  crystals, 
which  are  arranged  in  the  form  of  rays. 
It  is  found  chiefly  in  primitive  districts 
with  a  magnesian  basis.  There  are  three 
varieties, — the  crystallized,  the  asbestous, 
and  the  glassy. 

Actinolite  slate.  A  hornblendic  rock, 
composed  of  actinolite  and  felspar,  and 
easily  recognized  by  its  light-green  colour, 
and  the  elongated  form  or  fibrous  appear- 
ance of  its  principal  constituent  mineral. 

ACTINO'METER(aKTii/,  a  ray  of  light, 
p.eTpov,  a  measure).  An  instrument  for 
measuring  the  intensity  of  light.  This 
instrument  indicates  the  force  of  sun- 
shine at  the  Cape  of  Good  Hope  as  48° 
75',  while  ordinary  sunshine  in  England 
is  only  from  25°  to  30°. 

ACTION.  The  motion  which  one  body 
produces,  or  endeavours  to  produce,  in 
another.  Mechanical  action  is  exerted 
by  percussion  or  by  pressure ;  and,  in 
either  case,  the  force  exerted  by  the  act- 
ing body  is  repelled  in  an  equal  degree 
by  the  body  on  which  it  acts  :  the  stroke 
of  the  hammer  on  a  nail,  acts  upon  the 
former  equally  as  on  the  latter.  In  all  such 
cases,  the  counteracting  force  is  termed 
re-action;  and  it  is  a  law  in  Physics  that 
"  action  and  re-action  are  equal." 

ACTIVITY,  SPHERE  OF.  The  space 
within  which  the  action  of  a  body  pro- 
duces a  sensible  effect. 

A'CUBENE.  A  star  of  the  fourth 
magnitude,  in  the  southern  claw  of  Can- 
cer, marked  a. 

ACULEA'TA  (aculeus,  a  sting).  A 
group  of  Hymenopterous  insects,  in  which 
the  abdomen  of  the  females  and  neuters 
is  armed  with  a  sting  connected  with  a 
poison  reservoir.  The  antennae  are  twelve 
in  number  in  the  female,  and  thirteen  in 
the  male. 

ACU'LEATE  {aculeus,  a  prickle). 
Prickly ;  a  term  applied,  in  botany,  to  a 
surface  covered  with  prickles,  as  the  stem 
of  the  rose. 

B4 


ADD 


AD  H 


'  ACU'LEUS  (dim.  of  acus,  a  needle). 
A  prickle ;  a  hard  conical  expansion  of 
the  bark  of  certain  plants,  as  of  the  rose. 
It  is  distinguished  from  the  thorn  or 
spine  by  the  nature  of  its  tissue :  the 
prickle  consists  of  cellular,  the  spine  of 
woody  tissue. 

ACU'MINATE  {acumen,  a  sharp  point). 
Pointed ;  ending  in  a  tapering,  acute  point, 
as  the  leaf  of  Salix  alba. 

ACU'TE  (acutus,  sharp).  This  term, 
in  Geometry,  is  opposed  to  obtuse:  an 
acute  angle  is  that  which  is  less  than  a 
right  angle,  or  does  not  subtend  an  angle 
of  90  degrees ;  an  acute-angled  triangle 
is  that  which  has  three  acute  angles  ;  an 
acute-angled  cone  is  that  whose  opposite 
sides  form  au  acute  angle  at  the  vertex. 
In  Acoustics,  the  term  acute  is  opposed 
to  grave,  and  denotes  that  the  sound  of 
the  voice  or  of  a  musical  instrument  is 
raised  with  respect  to  some  other 
sound. 

ADA'GIO.  An  Italian  term  signifying 
slowly,  and  employed  to  indicate  the 
slowest  movement  in  music.  The  de- 
grees of  movement  are  as  follows :  adagio, 
very  slow;  largo,  slow;  andante,  mode- 
rate ;  allegro,  quick ;  presto,  very  quick. 

A'DAMANT  (a,  priv.,  6afxa<a,  to  sub- 
due). This  term,  which  simply  means 
unconquerable,  is  usually  applied  to  the 
hardest  metal,  probably  steel.  By  Plato 
it  was  applied  to  a  compound  of  gold  and 
steel.  By  others  it  has  been  referred  to 
the  diamond. 

ADAMA'NTINE  SPAR.  The  crys- 
tals of  Corundum,  so  named  from  their 
approaching  to  adamant  in  hardness.  It 
is  a  variety  of  crystallized  alumina,  nearly 
resembling  the  sapphire  in  composition, 
and  is  usually  found  in  granite,  and 
sometimes  in  primary  limestone. 

ADDITION  (addo,  to  give  to.  The 
operation  of  adding,  or  taking  together, 
any  numbers  or  magnitudes,  with  the 
view  of  finding  the  resulting  number  or 
magnitude,  which  is  called  their  sum. 
The  sign  of  this  operation  is  + ,  which  is 
read  plus,  or  more :  thus,  a  +  b  signifies 
that  the  number  indicated  by  b  is  to  be 
added  to  that  indicated  by  a,  and  repre- 
sents the  sum  of  a  and  b. 

A'DDITIVE  and  SUBTRACTIVE. 
Terms  sometimes  applied  to  algebraical 
quantities,  in  the  same  sense,  respec- 
tively, as  positive  and  negative,  and  with 
the  advantage  of  greater  precision  of 
meaning. 

ADDUCTOR  MUSCLE  {adduco,  to 
draw  to).    A  muscle  whose  office  is  to 


draw  one  part  of  the  body  to  another,  as 
that  which  closes  the  two  parts  of  a 
bivalve  shell ;  in  this  case,  its  base  or 
insertion  is  indicated  by  an  irregular  de- 
pression in  each  valve,  termed  the  mus- 
cular impression.     See  Abductor. 

ADE'LPHIA  (a<kA06t,  a  brother). 
Literally,  a  brotherhood ;  a  term  applied 
in  botany  to  a  combination  of  the  fila- 
ments of  the  stamens  into  a  single  mass. 
Thus,  if  there  is  only  one  combination, 
as  in  Mallow,  the  filaments  are  said  to  be 
mon-adelphous ;  if  there  are  two,  as  in 
Pea,  they  are  di-adelphous ;  if  three,  as  in 
some  species  of  St.  John's  Wort,  they  are 
tri-adelphous ;  if  many,  as  in  Melaleuca, 
they  are  called  poly-adelphous.  The 
tube  formed  by  the  union  of  monadel- 
phous  filaments  is  termed,  by  Mirbel, 
androphorum. 

A'DEPT  (adipiscor,  to  obtain).  A 
characteristic  denomination  of  those  al- 
chemists, who  were  supposed  to  have  ob- 
tained the  grand  objects  of  their  inquiry, 
viz.  the  philosopher's  stone  and  the  uni- 
versal remedy. 

ADFE'CTED  or  AFFE'CTED.  A 
term  applied  in  Algebra  to  those  equations 
into  which  the  first  or  simple  power  enters 
as  well  as  the  square  of  the  unknown 
quantity ;  thus  a2  +  4x  =  45.  When  ap- 
plied to  a  quantity,  it  denotes  that  the 
quantity  has  a  co-efficient,  or  proper  sign ; 
thus,  in  the  quantity  +  5x,  the  quantity  x 
is  said  to  be  affected  with  the  co-efficient 
5,  and  with  the  positive  sign  +.  See 
Quadratics. 

ADHE'SION  (adhcereo,  to  stick  to). 
A  term  denoting,  in  physics,  the  force  by 
which  bodies,  whether  similar  or  dissi- 
milar, adhere  together,  when  their  sur- 
faces are  brought  in  contact.  It  differs 
from  cohesion,  which  denotes  the  force  by 
which  the  particles  of  a  body  are  held 
together.  Adhesion  relates  to  masses, 
cohesion  to  molecules :  a  drop  of  water 
maintains  its  globular  form  by  cohesion  ; 
it  moistens  other  bodies,  as  lime  and 
sand,  by  adhesion  ;  and,  on  its  solidifica- 
tion in  the  form  of  mortar,  the  adhesion 
becomes  cohesion. 

ADHE'SION,  VEGETABLE (od/^reo, 
to  stick  to).  A  property  of  vegetable 
tissue,  by  which  contiguous  parts  grow 
together.  Opposite  leaves  may  adhere, 
and  become  connate ;  sepals  may  adhere 
entirely,  forming  a  gamosepalous  calyx, 
or  partially,  and  constitute  a  labiate  ca- 
lyx ;  petals  may  adhere,  forming  a  gamo- 
petalous  corolla  ;  stamens  may  adhere, 
and    form    an    adelphia ;     carpels    may 


ADU 


AER 


adhere,  and  form  a  syncarpous  or  com- 
pound fruit. 

ADHIL.  A  star  of  the  sixth  magni- 
tude, on  the  garment  of  Andromeda. 

A'DIPOCERE  (adeps,  fat,  cera,  wax). 
The  fatty  and  spermaceti-like  substance 
into  which  muscle  is  converted  by  long 
immersion  in  water  or  spirit,  or  by  burial 
in  moist  earth. 

ADIPOCERE  MINERAL.  A  fatty 
matter,  resembling  adipocere,  found  in 
the  argillaceous  iron  ore  of  Merthyr. 

A'DIT  (aditus,  an  approach).  A  sub- 
terraneous passage,  in  mining  operations, 
beginning  at  the  bottom  of  a  valley,  and 
continued  up  to  the  vein,  for  the  purpose 
of  carrying  out  the  minerals  and  of  draw- 
ing off  the  water. 

A'DJACENT  ANGLES.  The  two 
angles  formed  at  the  point  where  one 
straight  line  falls  upon  another,  the 
former  line  constituting  one  of  the  sides 
of  each  angle,  and  the  latter  line  consti- 
tuting the  other  side  of  each.    See  Angle. 

A'DJECTIVE  (adjicio,  to  add  to).  In 
grammar,  a  word  which,  being  added  to  a 
noun,  qualifies  or  limits  its  application. 
Adjectives  are  termed  attributive,  when 
they  denote  a  quality  ;  numeral,  when 
they  refer  to  number.  The  possessive 
pronouns  might  be  termed  pronominal 
adjectives ;  the  demonstrative  and  distri- 
butive pronouns  may  also  be  referred  to 
the  adjective,  as  they  both  precede  and 
designate  nouns,  but  never  supply  their 
place. 

A'DJECTIVE  COLOURS.  Colours 
which  require  the  intervention  of  some 
base  or  mordaunt,  in  order  to  enable  them 
to  adhere  to  the  cloth,  in  the  manufac- 
ture of  dye-stuffs. 

ADNATE  {adnatus,  grown  to)  Grown 
to  any  thing,  as  the  anther  to  the  face  of 
the  filament  in  polygonum.     See  Innate. 

ADOLE'SCENCE  (adolesco,  to  grow). 
The  period  of  life  in  which  the  body  has 
acquired  its  utmost  development ;  com- 
mencing at  puberty,  and  terminating,  in 
the  male,  about  the  twenty-fifth,  and  in 
the  female,  in  the  twenty-first  year. 

ADO'PTER,  or  ADAPTER.  A  vessel 
with  two  necks  placed  between  a  retort 
and  a  receiver,  and  serving  to  measure 
the  length  of  the  neck  of  the  former. 

ADULA'RIA.  A  sub-species  of  pris- 
matic felspar,  the  finest  specimens  of 
which  are  procured  at  Adula,  on  the 
summit  of  St.  Gothard.  By  lapidaries  it 
is  termed  moonstone,  from  the  play  of 
light  exhibited  by  the  arrangement  of  its 
crystalline    structure.    A   variety    from 


Siberia  is  called  sunstone  by  jewellers, 
and  to  this  variety  the  avanturine  felspar 
of  Archangel  appears  to  belong. 

ADVENTITIOUS  (advenio,  to  come 
to).  Accidental;  casual ;  abnormal;  that 
which  comes  from  some  unusual  source. 
In  botany,  it  denotes  any  thing  developed 
out  of  the  ordinary  course,  as  aerial 
roots,  extra-axillary  buds,  &c. 

A'DVERB  (ad,  to,  verbum,  a  word). 
In  grammar,  a  word  which  qualifies  a 
verb,  adjective,  participle,  or  even  an- 
other adverb,  and  generally  indicates 
time,  place,  quantity,  or  manner.  The 
adverb  is  closely  related  to  the  adjective, 
and  seems  to  have  been  originally  con- 
trived to  express  compendiously  in  one 
word  what  must  otherwise  have  required 
two  or  more. 

jEO'LIAN  HARP  (JEolus,  the  god  of 
the  winds).  A  musical  instrument  con- 
sisting of  a  simple  box  of  wood,  with 
four  or  five  strings,  two  or  three  feet 
long,  fastened  at  each  end.  These  are 
tuned  in  unison,  so  that,  when  made  to 
vibrate  with  force,  they  produce  the  same 
tones.  But,  when  suspended  in  a  gentle 
breeze,  each  string,  according  to  the 
manner  of  force  in  which  it  receives  the 
blast,  either  sounds  as  a  whole,  or  is  di- 
vided into  several  parts. 

jE'OLI  PILE  (Moli  pila,  ball  of  iEolus). 
A  steam  globe,  or  hollow  sphere  of  copper 
or  brass,  with  a  small  orifice  for  the  in- 
sertion of  a  tube,  for  illustrating  both  the 
meohanical  and  thermal  properties  of 
steam. 

jEPI'NUS'S  THEORY.  A  theory  by 
which  the  phenomena  of  magnetism  are 
referred  to  the  agency  of  a  peculiar 
fluid,  having  properties  very  similar  to 
those  of  the  electric  fluid  in  the  hypo- 
thesis of  Franklin,  but  which  act  only 
upon  ferruginous  bodies  and  nickel.  The 
particles  of  this  fluid  repel  one  another 
with  a  force  which  decreases  as  the  dis- 
tance increases,  and  they  are  attracted  by 
the  particles  of  iron  with  a  force  varying 
according  to  the  same  law.  This  theory 
further  requires  the  supposition  that  the 
particles  of  iron  repel  one  another  accord- 
ing to  the  same  law. 

^EQUILATERAL  (aqua  latera  ha- 
bens).  Having  equal  sides,  as  applied 
to  triangles  which  have  all  their  sides 
equal. 

AERA'TION  (aer,  air).  The  impregna- 
tion of  a  liquid  with  carbonic  acid  gas ; 
or  simply  the  saturation  of  a  liquid  with 
air. 

AERIAL  ACID  (aer,  air).  A  name 
B5 


AER 


^ETH 


given  by  Bergman  n  to  carbonic  acid,  from 
an  idea  tbat  it  entered  into  the  compo- 
sition of  atmospheric  air. 

A'ERIFORM  {aer,  air,  forma,  like- 
ness). Air-like  ;  a  term  applied  to  gase- 
ous fluids,  from  their  resemblance  to 
common  air.     See  Gas. 

A'ERO-DYNA'MICS  (iJjp,  tepo?,  air, 
Suva/jus,  power).  The  science  which  treats 
of  the  motion  of  the  air,  and  of  the  me- 
chanical effects  of  the  air  in  motion. 

A'EROGRAPHY  {atjp,  atpos,  the  air, 
7pa0o>,  to  describe).  A  description  of  the 
nature,  properties,  and  limits  of  the  at- 
mosphere. 

A'EROLITE  {drjp,  aepo?,  air,  X«'0o?,  a 
stone).  A  meteoric  stone,  or  mineral 
mass,  which  falls  through  the  air,  accom- 
panied with  the  disengagement  of  light, 
and  a  noise  like  thunder.  These  masses 
invariably  contain  iron,  cobalt,  or  nickel, 
or  a  combination  of  these  three  metals* 
in  union  with  various  earthly  substances. 
They  have  a  specific  gravity  of  from  3.3 
to  4.3,  and  are  more  or  less  magnetic. 

AERO'METER  (<i;7P,  a'epop,  air,  Me- 
rpov,  a  measure).  An  instrument  con- 
structed by  Dr.  M.  Hall,  for  ascertaining 
the  changes  in  the  temperature  of  tbe 
atmosphere;  in  the  barometrical  pres- 
sure ;  in  the  external  and  internal  heights 
of  the  fluid  in  the  pneumatic  trough ; 
and,  when  this  trough  contains  water,  for 
the  elevation  and  precipitation  of  aqueous 
vapour. 

A'ERONAUTICS  {arjp,  aepor,  air, 
vaimKoc,  belonging  tc  ships).  The  art  of 
navigating  the  air,  by  means  of  a  balloon. 

A'EROPHYTES  (arjp,  afpor,  the  air, 
Qvtov,  a  plant).  Plants  which  live  ex- 
clusively in  air,  as  distinguished  from 
hydrophytes,  which  live  in  water. 

AERO'SCOPY  (u»7p,  depor,  air,  a-KOTreco, 
to  observe).     The  observation  of  the  air. 

A'EROSTAT  {^p,  tepor,  the  air, 
o-racrt?,  a  standing).  An  air-balloon,  or 
hollow  spherev  composed  of  flexible  and 
air-tight  materials,  and  filled  with  some 
elastic  fluid  whose  specific  gravity  is 
much  less  than  that  of  atmospheric  air. 
See  Montgolfier. 

A'EROSTA'TICS  {dhp,  depor,  air, 
o-Tao-tf,  a  standing).  The  science  which 
treats  of  the  equilibrium  of  air  and  other 
elastic  fluids. 
.  A'EROSTA'TION  {atjp,  aepo?,  the  air, 
o-Tdo-tp,  a  standing).  A  science  depend- 
ing on  the  statical  operations  of  our 
atmosphere,  and  exhibited  in  raising 
heavy  bodies  into  the  air,  by  the  buoyancy 
of  gases  of  small  specific  gravity.  In 
10 


other  words,  it  is  the  science  which 
teaches  the  equilibrium  of  bodies  sup- 
ported in  air. 

iERU'GO  {ces,  copper).  Verdigris; 
an  impure  subacetate  of  copper,  formed 
by  placing  plates  of  the  metal  in  contact 
with  the  vapours  of  vinegar. 

jE'SCULA'CEjE.  The  Horse-Chestnut 
tribe  of  Dicotyledonous  plants,  named 
from  the  genus  iEsculus.  Trees  or 
shrubs,  with  leaves  opposite;  flowers  un- 
symmetrical;  stamens  7  or  8,  unequal, 
hypogynous ;  ovary  3-celled ;  fruits  1-2 
or  3-valved ;  seeds  large,  with  a  broad 
hilum,  exalbuminous. 

ESTHETICS  {a'laOnw,  perception). 
That  science  which  refers  the  first  prin- 
ciples in  the  arts  to  sensation  and  senti- 
ment, as  distinguished  from  mere  in- 
struction and  utility.  "  Art,"  says  Men- 
zel,  "is  not  the  result  of  understanding 
alone ;  the  inspiration  of  the  artist  has 
been,  and  ever  must  be,  the  source  of 
that  which  gives  aesthetic  value  to  his 
productions." 

^ESTIVATION  {astivus,  belonging  to 
summer).  Prcefloration.  A  botanical 
term,  denoting  the  manner  in  which  the 
floral  envelopes  are  arranged  with  respect 
to  each  other,  before  their  expansion 
Thus,  in  the  Umbelliferae,  the  aestivation 
is  valvate ;  in  Rosa,  it  is  quincuncinl ;  in 
papilionaceous  flowers,  it  is  vexillary, 
&c.     See  Vernation. 

jE'STUARY  (cestuarium,  a  firth).  An 
arm  of  the  sea  in  which  the  tide  ebbs  and 
flows.  A  channel  of  a  river  contiguous 
to  the  sea,  in  which  the  influence  of  the 
tides  is  perceptible,  without  distinct  cur- 
rent. 

jE'THEO'GAMOUS  (d<70nf,  unusual, 
idnos,  marriage).  A  term  applied  to 
what  are  otherwise  called  cryptogamous 
plants,  from  the  notion  that  their  mode 
of  reproduction  is  of  an  unusual  rather 
than  of  a  hidden  nature.  The  term  would 
be  more  correctly  written  aetheogamous. 

jETHER  (a\0hp,  ether).  A  highly 
limpid,  volatile,  and  inflammable  fluid, 
produced  by  the  action  of  acids  on  alco- 
hol. 

JE'THIOPS  (eu0«,  to  burn,  Ss\j/,  the 
eye  or  countenance).  A  designation  of 
various  chemical  compounds,  derived 
from  their  black  appearance,  resembling 
that  of  the  jEthiop.  Thus  we  have 
cethiops  mineral,  or  the  black  sulphuret 
of  mercury ;  cethiops  per  se,  or  the  grey 
oxide  of  mercury  ;  cethiops  martial,  an 
old  name  of  the  deutoxide  of  iron ;  and 
vegetable  cethiops,  a  species  of  charcoal, 


AFF 


AFF 


prepared  by  burning  the  fucus  vesiculo- 
sus  in  the  open  air,  and  reducing  it  to  a 
black  powder. 

iE'THOGEN  {aWmv,  brilliant,  yeivofxat, 
to  become).  A  compound  of  boron  and 
nitrogen,  lately  discovered  by  Mr.  Bal- 
main.  It  gives  a  brilliant  phosphorescent 
light  when  heated  before  the  blowpipe. 

JE'THRIOSCOPE  {atOpia,  serene  wea- 
ther, o-K07rt'o>,  to  examine).  An  instru- 
ment invented  by  Sir  John  Leslie  for 
indicating  the  power  of  the  clouds  in 
preventing  radiation.  It  consists  of  the 
differential  thermometer,  having  one  of 
the  balls  excluded  from  the  light,  and 
the  other  placed  in  a  polished  metallic 
cup.  Exposed  to  a  clear  part  of  the  sky, 
the  heat  radiated  from  it  escapes  rapidly, 
and  the  temperature  falls  ;  exposed  to  a 
cloud,  the  radiated  heat  is  restored,  and 
there  is  no  reduction  of  temperature. 

jETIO'LOGY  {atria,  a  cause,  \6yos,  a 
treatise).  That  branch  of  medical  sci- 
ence which  treats  of  the  causes  of  dis- 
ease. 

AETI'TES  LAPIS  (ue-ror,  an  eagle). 
Eagle-stone;  a  variety  of  iron  ore,  so 
called  from  the  belief  that  it  was  found 
in  the  nest  of  the  eagle,  where  it  was 
supposed  to  prevent  the  eggs  from  be- 
coming rotten. 

AFFINITY,  CHEMICAL  (affinitas, 
relationship).  That  kind  of  attraction 
by  which  certain  substances,  when  placed 
in  contact,  exhibit  a  tendency  to  combine 
with  each  other,  forming  compounds  dif- 
fering in  all  their  essential  qualities  and 
actions  from  their  constituent  ingre- 
dients, and  constituting  distinct  species 
of  matter.  The  actual  phenomena  of 
combination  suggest  the  idea  of  peculiar 
attachments  and  aversions  subsisting  be- 
tween different  bodies  ;  and  it  was  in  this 
figurative  sense  that  the  terra  affinity 
was  first  applied  by  Boerhaave  to  a  pro- 
perty of  matter. 

1.  Single  affinity  is  the  property  by 
which  two  elementary  bodies  combine, 
as  when  oxygen  combines  with  lead, 
forming  a  white  oxide. 

2.  Single  elective  affinity  is  the  property 
by  which  a  body  exhibits  a  preference  in 
combining  with  another,  rather  than  with 
a  third,  a  fourth,  &c.  Thus  nitric  acid 
has  an  -affinity  for  magnesia ;  it  has  also 
an  affinity  for  lime ;  but,  on  mixing 
these  three  substances  together,  only  one 
of  the  affinities  is  obeyed  :  the  nitric  acid 
combines  with  the  lime,  leaving  the 
magnesia  altogether  unaffected. 

3.  Double  elective  affinity  is  the  pro- 

11 


perty  by  which  two  compounds  are  de- 
composed, and  a  double  affinity  exhibited. 
Thus,  when  carbonate  of  soda  is  added 
to  nitrate  of  lime,  carbonate  of  lime  is 
instantly  formed  and  precipitated,  nitrate 
of  soda  being  formed  at  the  same  time 
and  remaining  in  solution.  This  is  a 
case  of  complex  affinity,  connected  with 
double  decomposition. 

4.  Reciprocal  affinity  is  the  property 
by  which  bodies,  which  have  no  tendency 
to  unite,  are  made  to  combine  by  means 
of  a  third,  which  is  then  called  the  me- 
dium. Thus,  on  introducing  a  clean 
plate  of  platinum  into  a  mixture  of  oxy- 
gen and  hydrogen  gases,  the  gases  in 
contact  with  the  metallic  surface  in- 
stantly unite  and  form  water.  This  has 
been  termed  disposing  affinity,  and  the 
affinity  of  intermedium. 

5.  Quiescent  and  divellent  affinities  are 
terms  introduced  by  Kirwan.  The  former 
is  that  property  which  prevents  decom- 
position, by  maintaining  the  elements  of 
a  compound  body  in  their  existing  state. 
The  latter  favours  decomposition,  by 
tending  to  arrange  the  particles  of  a 
compound  in  a  new  form. 

6.  Elementary  affinity  is  that  which 
takes  place  between  the  elements  of  a 
body.  Resulting  affinity  occurs  only  in 
a  compound,  having  no  existence  with 
the  elements  of  that  compound. 

7.  Inductive  or  current  affinity  is  a  term 
expressive  of  the  peculiar  exhibition  of 
chemical  affinity  in  the  simple  voltaic 
circle.  The  idea  of  any  thing  like  a  cir- 
culation of  electricity  in  this  case  appears 
to  be  abandoned,  the  phenomena  admit- 
ting of  a  perfectly  intelligible  explanation 
when  referred  to  ordinary  chemical  affi- 
nity exerting  its  influence  at  a  dis- 
tance, by  an  inductive  or  circulating 
agency. 

AFFIRMATIVE.  A  term  employed 
in  logic  to  denote  the  essential  quality  of 
a  proposition  :  this  quality  is  affirmative 
when  the  copula  asserts  an  agreement 
between  the  predicate  and  the  subject ; 
negative,  when  it  denies  that  agreement. 
The  essential  quality  of  a  proposition  is 
therefore  determined  by  the  copula. 

1.  An  affirmative  quantity  in  algebra  is 
a  positive  quantity,  or  a  quantity  to  be 
added,  as  distinguished  from  a  negative 
quantity,  or  a  quantity  to  be  deducted. 

2.  An  affirmative  sign,  or  a  positive 
sign,  is  a  sign  of  addition,  and  is  marked 
+  ,  signifying  plus,  or  more.  See  Alge- 
braical signs. 

A'FFIX  {affigo,  to  fasten  to).    Suffix. 
B6 


AG  A 


AGO 


In  grammar,  a  particle  added  to  a  word, 
to  diversify  its  form,  or  alter  its  significa- 
tion ;  as  artful,  wealthy,  strengthen,  con- 
vulsion, &c.     See  Prefix, 

AFFLU'XUS  {affluo,  to  flow  to).  Forma 
specified.  Names  given  in  former  times 
to  a  supposed  reciprocal  influence  of  ter- 
restrial bodies ;  it  was  compared  to  the 
effect  of  a  magnet  on  iron,  and  of  amber 
on  chaff.  ' 

AGA'LMATOLI'TE  ( aTa\Ma,  an 
image,  Ai'0op,  a  stone).  Bildstein,  or 
figure-stone.  A  massive  mineral,  of  a 
grey,  brown,  flesh-red  colour,  sometimes 
spotted,  or  with  blue  veins.  It  has  been 
called  steatite  pagodite,  from  its  being 
carved  by  the  Chinese  into  grotesque 
figures.  It  is  found  at  Naygag  in  Trans- 
sylvania,  and  Glyderbach  in  Wales. 

AGA'MIDiE  {agama,  the  name  of  a 
lizard).  The  first  section,  according  to 
Cuvier,  of  the  Iguanian  Sauria,  charac- 
terized by  the  absence  of  palatal  teeth. 
All  the  agamoid  lizards  possess  the  pro- 
perty of  changing  their  colour ;  and  from 
this  circumstance,  perhaps,  the  name 
(afafiai,  to  wonder  at)  is  derived. 

A'GAMOUS  (a,  priv.,  -yd/uor,  mar- 
riage). Sexless ;  a  term  applied  by  some 
botanists  to  what  are  more  commonly 
called  cryptogamous  plants,  from  the 
notion  that  they  possess  no  sexual  cha- 
racters—that they  are  absolutely  destitute 
of  stamen  and  pistil. 

A'GARIC  (Agaria,  a  kingdom  of  Sar- 
matia).  The  generic  name  of  the  Mush- 
room tribe  of  the  Fungi  which  grow  in 
decaying  animal  or  vegetable  matter. 

AGARIC  MINERAL.  One  of  the 
purest  of  the  native  carbonates  of  lime, 
found  in  clefts  of  rocks,  and  named  from 
its  resemblance  to  the  agaric  in  texture 
and  colour.  It  has  been  considered  as  a 
variety  of  meerschaum.  The  Germans 
call  it  bergmehl,  or  mountain  meal ;  the 
Italians,  latte  di  luna,  or  moon-milk.  It 
is  the  argillo-murite  of  Kirwan,  the  talc 
pulverulent  silicifere  of  Haiiy. 

AGA'STRICA  (a,  priv.,  Yao-rJ/p,  the 
stomach).  Stomach-less ;  a  term  applied 
to  certain  animalcules,  which  were  sup- 
posed to  be  devoid  of  internal  digestive 
cavities. 

A'GATE  ('Ax«t^9,  the  name  of  a  river 
in  Sicily).  A  genus  of  semi-pellucid 
gems,  consisting  of  a  basis  of  chalcedony, 
with  variable  proportions  of  jasper,  ame- 
thyst, quartz,  opal,  heliotrope,  and  cor- 
nelian. The  finer  varieties  are  termed 
oriental ;  the  most  beautiful  British  spe- 
cimens are  known  by  the  name  of  Scotch 
12 


pebbles,  and  sometimes,  from  their  local- 
ity, Cairngorms. 

1.  Ribbon  agate  consists  of  alternate 
and  parallel  layers  of  chalcedony  with 
jasper,  quartz,  or  amethyst.  The  most 
beautiful  specimens  come  from  Siberia 
and  Saxony.  It  occurs  in  porphyry  and 
gneiss. 

2.  Brecciated  agate  consists  of  a  base 
of  amethyst,  containing  fragments  of 
ribbon  agate.     It  is  of  Saxon  origin. 

3.  Fortification  agate  is  found  in  no- 
dules of  various  imitative  shapes,  im- 
bedded in  amygdaloid.  This  occurs  at 
Oberstein  on  the  Rhine,  and  in  Scotland. 
On  cutting  it  across,  and  polishing  it, 
the  interior  zig-zag  parallel  lines  bear  a 
considerable  resemblance  to  the  plan  of  a 
modera  fortification.  In  the  very  centre, 
quartii  and  amethyst  are  seen  in  a  splin- 
tery mass,  surrounded  by  the  jasper  and 
chalcedony. 

4.  Mocha  stone  is  a  translucent  chal- 
cedony, containing  dark  outlines  of  ar- 
borization, like  vegetable  filaments,  sup- 
posed to  arise  from  mineralized  plants  of 
the  cryptogamous  class.  It  is  found  in 
Arabia. 

5.  Moss  agate  is  a  chalcedony  with  va- 
riously-coloured ramifications  of  a  vege- 
table form,  occasionally  traversed  with 
irregular  veins  of  red  jasper.  In  this 
and  the  preceding  species,  aquatic  con- 
fervas have  been  discovered,     lire. 

A'GGREGATE  {aggregatus,  herded 
together).  1.  A  term  applied  in  physics 
to  a  body  or  mass  composed  of  smaller 
bodies  or  masses.  The  smallest  parts 
into  which  an  aggregate  can  be  divided 
without  destroying  its  chemical  proper- 
ties, are  called  integrant  parts.  2.  Ag- 
gregate animals  are  animals  clustered 
together  in  a  common  enveloping  organ- 
ized substance,  as  the  polypes,  the  aca- 
lephae,  and  the  acephalous  mollusca. 
3.  In  botany,  the  term  is  applied  to 
parts  which  are  crowded  together,  as  the 
florets  of  the  compositae,  the  carpels  of 
ranunculaceae,  &c. 

AGO'MPHIA  (a,  priv.,  -yo^or,  a 
grinder).  Toothless  animals ;  a  term 
applied  by  Ehrenberg  to  those  rotifera 
whose  jaws  are  deprived  of  teeth. 

AGO'NIC  LINES  (a,  priv.,  ywi/ta,  an 
angle).  The  name  given  by  Prof.  August 
to  some  lines  existing  on  the  surface  of 
the  earth,  on  which  the  horizontal  needle 
points  to  the  true  north ;  in  other  words, 
where  the  magnetic  meridian  coincides 
with  the  geographical.  These  lines  of  no 
declination    are    two  in  number:    one, 


AIR 


ALA 


called  the  American  agone,  is  in  the 
western  hemisphere ;  the  other,  or  Asia- 
tic, is  in  the  eastern  hemisphere.  They 
extend  from  south  to  north,  but  they  do 
not  coincide  with  the  meridians  ;  for  they 
both,  especially  the  Asiatic,  intersect  the 
latter  lines  under  different  angles.  See 
Isogonic  lines. 

AIR  {di]p,  aer).  The  general  designa- 
tion of  a  gas,  or  permanently  elastic 
fluid.  Ethereal  air,  or  ether,  is  an  ima- 
ginary fluid,  supposed  to  fill  all  space 
beyond  the  atmospheres  of  the  earth  and 
other  planets.  Atmospheric  air  is  the 
gaseous  fluid  which  surrounds  the  earth, 
consisting,  when  pure,  of  20  parts  of 
oxygen,  and  80  of  nitrogen,  with  a  por- 
tion of  carbonic  acid,  varying  from  3  to  8 
parts  in  10,000  by  weight.  Air  which  is 
expanded,  or  rendered  less  dense  than 
usual,  is  said  to  be  rarefied;  that  which 
has  been  subjected  to  pressure,  is  said  to 
be  condensed. 

AIR-CELLS.  A  term  applied  to  cavi- 
ties in  the  stems  and  leaves  of  plants, 
which,  being  filled  with  air,  enable  the 
plants  to  float  in  water ;  also  to  mem- 
branous receptacles  in  birds,  by  means  of 
which  their  bodies,  being  permeated  by 
the  atmospheric  air,  are  adapted  for 
flight. 

AIR-GUN.  An  instrument  for  pro- 
jecting bullets,  resembling  a  common 
gun,  with  the  addition  of  a  hollow  ball 
or  reservoir,  into  which  air  is  introduced 
and  condensed  by  means  of  a  syringe. 
The  effects  of  the  apparatus  depend  on 
the  elasticity  and  compression  of  the 
air. 

AIR-PLANTS.  Plants  which  grow 
without  having  their  roo's  within  the 
earth.  It  was  supposed  that  they  were 
nourished  by  the  air ;  but  their  locality 
in  a  damp  atmosphere,  or  in  contact  with 
other  vegetables,  rather  suggests  the 
usual  mode  of  existence  There  are 
two  tribes  of  air-plants,  viz.,  the  Brome- 
liacece  and  the  Orchidacece. 

AIR-PUMP.  An  exhausting  syringe, 
or  pneumatic  apparatus  for  rarefying  the 
atmospheric  air  and  reducing  it  to  any 
required  degree  of  tenuity,  and  at  the 
same  time  exhibiting  the  circumstances 
which  attend  this  change  of  condition  as 
displayed  in  other  bodies. 

AIR-TIGHT.  That  degree  of  close- 
ness, in  any  vessel  or  tube,  which  pre- 
vents the  passage  of  air. 

AIR-VESSEL.  A  vessel  in  which  air 
is  condensed  by  pressure,  for  the  pur- 
pose of  employing  the  reaction  of  its 
13 


elasticity  as  a  moving  or  a  regulating 
power.  The  term  has  also  been  applied 
to  the  spiral  vessels  of  plants  and  to  the 
trachece  of  insects. 

A'LA.  The  Latin  term  for  a  wing. 
In  Ornithology,  it  denotes  the  pectoral 
extremity,  the  bones  of  which  support 
broad  folds  of  skin,  covered  with  feathers, 
and  adapted  for  flight.  In  Botany,  it  is 
the  lateral  petal  of  a  papilionaceous 
corolla. 

A'LABASTER  (d\d0a<rrpov,  a  calca- 
reous spar).  A  stone  usually  white,  re- 
sembling marble,  but  soft  enough  to  be 
scratched  by  iron.  The  term  is  said  to 
be  derived  from  Alabastron,  a  town  of 
Egypt.  1.  Gypseous  alabaster  is  a  natural 
semi-crystalline  sulphate  of  lime,  forming 
a  compact  gypsum  of  various  colours, 
and  employed  for  making  statues  and 
vases.  2.  Calcareous  alabaster  is  a  car- 
bnnate  of  lime,  deposited  by  the  dripping 
of  water  in  stalactitic  caves,  and  fre- 
quently found  as  a  yellowish-white  de- 
posit in  certain  fountains.  The  oriental 
alabaster  is  of  this  kind. 

A'LALITE.  Another  name  for  diop' 
side  or  mussite,  a  sub-species  of  oblique- 
edged  augite.  It  is  found  at  Piedmont,  in 
the  black  rock  at  Musa,  near  AH,  in  veins, 
along  with  epidote  or  pistacite,  and  hya- 
cinth-red garnets. 

ALA'NGIA'CEjE.  An  order  of  Dico- 
tyledonous plants,  named  from  Alangium, 
the  Malabar  name  of  one  of  the  genera. 
Large  trees,  with  leaves  alternate  ;  petals 
5-10 ;  stamens  2-4  times  as  numerous  as 
the  petals;  fruit  drupaceous,  esculent; 
seeds  albuminous,  fleshy,  pendulous. 

A'LANTINE.  An  amylaceous  sub- 
stance, procured  from  the  root  of  the 
Angelica  Arch  angelica,  an  umbelliferous 
plant. 

ALASMODO'NTIN^.  A  sub-family 
of  the  Unionidce,  unios,  or  river  mussels, 
named  from  the  genus  alasmodon. 

ALA'TE  (ala,  a  wing).  Winged  ;  a 
term  applied  to  any  body,  as  a  stem  or 
seed  of  a  plant,  which  is  bordered  by  a 
leafy  or  membranous  expansion  resem- 
bling a  wing. 

ALAU'DIN^E  (alauda,  a  lark).  Alau- 
dine  birds,  or  larks ;  a  family  of  the 
Cantatrices  of  Macgillivray,  intimately 
allied  to  the  Wagtails  on  the  one  hand, 
and  to  the  Thrushes  on  the  other.  They 
do  not  belong,  according  to  this  author, 
to  the  Conirostral  or  Thick-billed  birds, 
as  generally  supposed  ;  for  their  bill  i* 
differently  formed,  and  they  never  shell 
or  husk  seeds,  but  swallow  them  entire. 


AL  C 


ALE 


A'LBIN  {alius,  white).  An  opaque 
white  mineral  found  in  Bohemia.  It 
occurs  massive  in  aggregate  crystalline 
laminae. 

ALBI'NO  (albus,  white).  A  term  ap- 
plied hy  Dr.  Prichard  to  one  of  those 
varieties  of  mankind,  including  all  indi- 
viduals or  races  which  have  white  hair, 
and  are  also  distinguished  by  red  eyes. 
The  term.  Albino  is  derived  from  the  Por- 
tuguese, by  whom  it  was  applied  to  indi- 
viduals found  on  the  coast  of  Africa,  who 
resembled  the  negroes  in  every  respect 
except  in  colour.  These  negroes  were  also 
called  Leuccethiopes,  a  term  denoting 
white  negroes. 

A'LBITE.  Soda  Felspar.  A  silicate 
of  alumina,  resembling  felspar  in  its  pro- 
perties, with  the  substitution  of  soda  for 
potash.  It  occurs  in  crystals  under  the 
'form  of  hemitropes.  These  hemitropes 
are  formed  when  two  crystals  are  so 
joined  to  each  other,  that  the  upper  plane 
of  the  one  is  applied  upon  the  lower 
plane  of  the  other.    See  Cleavlandite. 

ALBU'MEN  {albus,  white).  One  of 
the  most  important  proximate  principles 
of  animal  bodies,  existing,  in  the  solid 
state,  in  several  of  the  textures  of  the 
body,  as  the  cellular  membrane,  the 
skin,  &c. ;  and,  in  the  liquid  state,  con- 
stituting the  principal  part  of  the  white 
of  egg.  Vegetable  albumen  closely  re- 
sembles animal  albumen,  and  appears  to 
be  an  ingredient  of  emulsive  seeds  gene- 
rally, and  to  exist  in  the  sap  of  many 
plants. 

ALBU'RNUM  {albics,  white).  The  ex- 
ternal, last  formed,  and  whiter  portion  of 
the  wood  of  exogenous  trees.  From  its 
being  the  channel  of  the  ascending  sap, 
it  is  commonly  called  sap-wood.  See 
Duramen. 

ALCA'RGEN;  ALCA'RSIN.  Arseni- 
cal compounds  derived  from  acetyl.  The 
former  is  synonymous  with  cacodylic 
acid  ;  the  latter,  with  oxide  of  cacodyl, 
and  known  as  the  liquor  of  Cadet. 

ALCE'DINiE  {alcedo,  the  king-fisher). 
Alcedine  birds,  or  King-fishers  ;  a  family 
of  the  order  Jaculatrices  of  Macgillivray, 
of  the  Insessores  of  other  writers.  See 
Halcyonidce. 

A'LCHEMY.  The  fanciful  search  after 
the  philosophers'  stone,  by  which  the 
baser  were  to  be  transmuted  into  the 
precious  metals ;  and  the  elixir  vitce,  by 
which  human  life  was  to  be  indefinitely 
prolonged.  Those  alchemists  who  were 
supposed  to  be  skilled  in  the  art  were 
termed  Adepts. 
14 


A'LCIlLE  {alca,  the  auk).  The  Auk 
or  Penguin  tribe ;  a  family  of  the  Nata- 
tores,  or  Swimming  birds,  which  exhibit 
the  most  remarkable  adaptation  of  struc- 
ture for  aquatic  habits,  their  short  feather- 
less  wings  being  admirable  representa- 
tives of  fins  or  paddles. 

A'LCOATES.  Crystalline  compounds 
formed  by  alcohol  with  several  of  the 
salts  which  it  dissolves.  Tney  corre- 
spond with  hydrates,  but  are  much  less 
stable. 

A'LCOHOL.  An  alchemical  term,  of 
Arabic  origin,  denoting  the  essence  of 
bodies,  separated  by  sublimation  from 
all  impurities.  It  now  signifies  ardent 
spirit  of  wine,  as  obtained  by  distillation 
and  subsequent  rectification  from  all 
liquids  which  have  undergone  vinous 
fermentation.  The  first  product  of  dis- 
tillation is  called  low  wine;  this,  on  re- 
distillation, becomes  raw  spirit,  and,  on 
repeating  the  process,  rectified  spirit.  In 
its  most  concentrated  state  it  is  termed 
absolute  alcohol,  and  is  then  free  from 
water. 

A'LCOHO'METER  {alcohol,  fxirpov,  a 
measure).  An'  instrument,  also  called 
cenometer,  for  ascertaining  the  quantity 
of  alcohol  contained  in  a  vinous  liquid. 

A'LCYONITES.  A  general  term  for 
the  fruit-like,  spongiform  fossils  common 
in  chalk  formations.  They  are  fossil 
alcyonia,  or  zoophytes  nearly  allied  to 
sponges,  the  production  or  habitation  of 
polypi. 

ALDE'BARAN.    The  Arabic  name  of 
a  star  of  the  first  magnitude,  marked  a 
Tauri,  situated  in  the  eye  of  the  constel- 
lation Taurus.    It  is  the  bright  star  in 
the  group  of  the  Hyades.     It  frequently^ 
suffers  occultation  by  the  moon,  when  the  I 
ascending  node  is  in  Virgo,  and  exhibits  \ 
the   phenomenon  of  projection   on   the  I 
moon's  disk.  — -^ 

A'LDEHYDE.  A  colourless  liquid, 
formed  by  the  action  of  oxidating  bodies 
upon  alcohol,  by  which  two  atoms  of  hy- 
drogen are  abstracted,  and  the  elements 
of  aldehyde  left.  Its  name  is  derived 
from  the  words  oZcohol  dehydrogena,- 
tus:  it  is,  in  fact,  alcohol  minus  hydro- 
gen. 

ALDERA'MIN.  A  star  of  the  third 
magnitude  in  the  northern  constellation 
Cepheus. 

ALDHA'FERA.  A  star  of  the  third 
magnitude  in  the  constellation  Leo. 

ALECTO'RIDES  (dX&rttp)  a  cock). 
A  tribe  of  gallinaceous  or  rasorial  birds, 
including  the  curassow  and  others  which 


ALG 


ALG 


resemble  the  common  fowl  in  the  form  of 
the  beak.    See  Cracidce. 

ALE'MBIC.  A  chemical  vessel,  em- 
ployed in  distillation,  and  consisting  of  a 
body,  cucurbit,  or  matrass,  which  serves 
as  a  boiler,  and  a  head,  or  capital,  with  a 
pipe  and  receiver. 

A'LEMBROTH  SALT.  A  compound 
of  bichloride  of  mercury  and  sal  ammo- 
niac ;  the  salt  of  wisdom  of  the  alchemists. 

A'LGiE  {alga,  a  sea-weed).  Algacece. 
The  Sea-weed  tribe  of  Cellular  or  Crypto- 
gamic  plants.  Leafless,  flowerless  plants, 
without  any  distinct  axi3  of  vegetation, 
growing  in  water.  Reproductive  matter, 
either  absent  or  contained  in  the  joints 
of  the  filaments,  or  deposited  in  peculiar 
thecae  formed  in  the  substance  of  the 
frond.  Sporules  without  any  proper  in- 
tegument. 

1.  Jointless  Algce.  These  comprise  all 
the  broad  membrane-like  sea  and  fresh- 
water species,  as  well  as  the  large  and 
tough  tangles  and  dulses  so  common  on 
our  coasts.  The  genera  fucus  and  ulva 
belong  to  this  division  of  algae. 

2.  Jointed  Algce.  These  are  generally 
termed  Conferva;,  and  comprise  the 
greater  number  of  fresh-water  species, 
and  many  of  marine  station.  They  con- 
sist of  thread-like  jointed  tubes. 

3.  Disjointed  Algce.  These  are  cha- 
racterized by  their  original  or  final  spon- 
taneous separation  into  distinct  frag- 
ments, which  have  a  common  origin,  but 
an  individual  life.  They  constitute  the 
organic  limits  of  the  animal  and  the 
vegetable  kingdoms. 

A'LGAROTH,  POWDER  OF.  An 
oxichloride  of  antimony,  precipitated  on 
throwing  a  concentrated  solution  of  the 
chloride  into  water,  and  named  after  a 
physician  of  Verona. 

A'LGEBRA.  The  science  which  teaches 
to  reason  about  indeterminate  quantities 
by  means  of  letters  of  the  alphabet,  and 
certain  signs  and  symbols,  which  are  em- 
ployed to  represent  both  the  quantities 
themselves  and  the  manner  in  which 
they  are  connected  with  other  quantities. 
It  is,  in  fact,  universal  arithmetic.  The 
term  algebra  is  derived  from  some  Arabic 
words,  signifying  restoration  and  reduc- 
tion. 

ALGEBRA'IC.  An  expression  is  said 
to  be  algebraic,  as  distinguished  from 
transcendental,  when  its  number  of  terms 
is  finite,  and  when  each  term  contains 
only  addition,  subtraction,  multiplica- 
tion, and  division,  and  extraction  of 
roots,  the  exponents  of  which  are  given. 
15 


Thus,  all  infinite  series,  as  well  as  ex- 
pressions containing 

log.  x,  a*,  sin.  x,  cos.  x,  &c, 
though  used  in  Algebra,  in  the  widest 
sense  of  the  word,  are  properly  said  to  be 
not  algebraic,  but  transcendental.  Simi- 
larly, a  curve  is  said  to  be  algebraic  when 
its  equation  contains  no  transcendental 
quantities. 

ALGEBRA'IC  CURVE.  A  curve  of 
which  the  relation  between  the  abscissa 
and  the  ordinates  is  expressed  by  an 
algebraic  equation,  or  an  equation  of 
which  the  terms  contain  only  algebraic 
quantities.  This  is  also  called  a  geome- 
trical curve,  in  contradistinction  to  a 
mechanical  or  transcendental  curve. 

ALGEBRAIC  GEOMETRY.  A  name 
given  to  the  application  of  Algebra  to  the 
solution  of  geometrical  problems. 

ALGEBRA'ICAL     SIGNS.       Certain 
signs  used  in    algebraical    and    mathe- 
matical operations,  to  denote  the  relation 
of  numbers,  magnitudes,  and  quantities. 
The  characters  with  which  they  are  used 
are  either  the    arithmetical   figures,   as 
denoting  numbers,  or  the  letters  of  the 
alphabet,    as    denoting    magnitudes    or 
quantities.      The  explanation    of  these 
signs  is  as  follows  : — 
=  Equality,  denotes  that  the  numbers 
or    quantities    between    which   it    is 
placed  are  equal  to  each  other :  as  2 
and  2  =  4. 
+  Addition,    generally    called    plus,    a 
Latin  word  for  more:  it  denotes  that 
the  numbers,  or  quantities  between 
which  it  is  placed,  are  to  be  added  to- 
gether :   as  3  +  2,   or  3  more  2,   are 
equal  to  5  ;  or  3  +  2=5. 
—  Subtraction,   called    minus,  meaning 
less :  it  is  placed  between  numbers  or 
quantities,  and  denotes  that  the  num- 
ber, &c,  placed  after  it,  is  to  be  sub- 
tracted from  that  which  is  before  it  • 
as  5  — 2=  3. 
X  or  •  ,  Composition,  or  Multiplication, 
denotes    that  the  numbers    between 
which  it  is  placed  are  to  be  multiplied 
by  each  other,  or  together:  as  5x3, 
or  5  •  3  =  15.     In  numbers  it  is  best 
to  use  x,  as  •  is  apt  to  be  mistaken 
for  a  decimal  point.    With  letters  it 
is    indifferent  which    is    used ;    and 
single  letters   are  understood    to  be 
multiplied  where  there  is  no  sign  be- 
tween them :  as  a  b  denotes  the  pro- 
duct or  result  of  the  multiplication  of 
the  two  numbers  represented    by  a 
and  b.    Numbers  multiplied  together 
are  called  factors. 


ALGEBRAICAL      SIGNS. 


-5-  Resolution,  or  Division,  denotes  that 
the  number  before  it  is  to  be  divided 
by  the  number  after  it :  as  15  -j-  3  =  5. 
When  the  number  after  the  sign  is 
greater  than  that  before  it,  the  quo- 
tient, or  result  of  the  division,  cannot 
be  expressed  in  a  common  number, 
because  it  is  less  than  1,  which  is  the 
least  common  number.  In  these  cases 
the  quotient  is  indicated  by  placing 
the  number  to  be  divided  above  a  line, 
and  the  divisor  below.  Thus  the  quo- 
tient of  3  -J-  4  is  expressed  by  f .  When 
we  require  only  to  express  the  divi- 
sion and  not  perform  it,  the  fraction 
♦  is  sufficient :    as  ^  is   the   same   as 

15  +-  3.  Arithmetical  operations  can- 
not be  performed  with  letters,  and 
thus  the  fraction  is  the  only  form  in 
which  we  can  point  out  the  dividing 
of  one  letter  by  another :  as  ~  is  the 
only  way  in  which  we  can  express  the 
quotient  of  a-i-b. 
I  Ratio,  denotes  that  the  numbers  or 
quantities  between  which  it  is  placed 
have  some  relation  or  proportion  to 
each  other.  In  expressing  ratios  that 
are  equal,  instead  of  =,  the  usual  sign 
of  equality,  ;  ;  is  used.  Thus  the 
expression  a  \  b  \\  c  \  d,  means 
that  as  a  is  to  b  so  is  c  to  d;  and 
2  ;  4  ::  6  :  12,  as  2  is  to  4  so  is  6 
to  12.  Any  one  relation  of  the  mag- 
nitude or  value  of  one  thing,  or  quality, 
is  called  a  ratio. 

>  Majority,  denotes  that  the  number  or 
quantity  which  is  placed  before  it  is 
greater  than  that  which  follows:  as 
a  >  b,  that  the  quantity  expressed 
by  a  is  greater  than  that  represented 
by  b. 

<  Minority  is  the  reverse  of  majority, 
as  c  K.  d  expresses  that  the  quantity 
c  is  less  than  that  of  d. 

=,  >•  and  <,  are  used  to  denote  the  re- 
lations of  ratios,  or  proportions,  as 
well  as  of  single  numbers  and  quan- 
tities :  thus  a  \  b  =  c  \  d,  means  that 
a  is  the  same  part  or  portion  of  b  that 
c  is  of  d;  a  \  b>  c  \  d,  means  that 
a  is  a  greater  part  of  b  than  c  is  of  d ; 
and  a  '.  b  <  c  '.  d,  means  that  a  is  a 
less  part  of  b  than  c  is  of  d.  The 
same  may  be  expressed  by  making 
the  first,  or  antecedent  term  of  each 
ratio,  numerator  of  a  fraction,  and  the 
last  or  consequent  term,  denominator. 

Thus  "J  -5-i    *>J'andT<^'are 
respectively  the  same  as,  a  *  b  —  c  \  d, 
16 


a  \  b  >  c  ;  d,  and  a  *  b  <  c  \  d. 
When  ratios  vary,  the  signs  are  con- 
veniently written  =  ,  >,   <. 

Connexion  {vinculum,  or  tie)  drawn 

over  numbers  or  quantities,  connected 
by  signs,  or  the  enclosing  of  such  be- 
tween parenthetical  characters,  de- 
notes that  they  are  to  be  taken  as 
one,  that  is,  as  the  single  number  or 
quantity  that  would  result  after  all 
the  operations  were  performed.  Thus, 
8+6TT,  or  (8+fi)+-7,  denotes  that 
the  sum  of  8  and  6  is  to  be  divided 
by  7,  and  is  the  same  as  \f,  or  2 ;  but 
8+6 +-7,  without  the  sign  of  con- 
nexion, is  8f.  Again,  24  — 3  x  8,  or 
(24— 3)x8,  is  the  same  as  21x8,  that 
is,  168;  but  if  the  sign  of  connexion 
be  taken  away,  it  becomes  24 — 24, 
or  0. 

*  a  Power.  A  number  or  letter  written 
over  the  right  of  another  in  a  smaller 
character  is  called  an  exponent,  and 
denotes  that  the  number  or  letter 
over  which  it  is  written  is  understood 
to  be  used  as  a  factor  in  multiplica- 
tion as  often  as  is  expressed  by  the 
exponent.  Thus  43  is  the  same  as 
4x4x4,  or  64.  An  expression  of 
this  kind  is  called  a  power  of  the 
number  or  quantity  to  which  the  ex- 
ponent is  affixed,  and  that  number  or 
quantity  is  called  the  root.  The  per- 
forming of  the  multiplications  is 
called  involution;  and  the  number  of 
multiplications  is  always  one  less  than 
the  number  expressed  by  the  expo- 
nent, because  two  factors  are  required 
for  the  first  multiplication,  and  one 
additional  factor  for  every  succeeding 
one.  If  the  root  consist  of  several 
numbers  or  letters,  they  must  be  in- 
closed in  parentheses,  or  placed  under 
a  vinculum. 

\/  a  Root.  When  a  number  or  letter  is 
considered  as  a  power,  the  root  of  it 
is  denoted  by  placing  the  sign  *J 
before  it,  and  writing  the  exponent 
over  the  sign,  in  the  place  of  the  small 
letter  n :  thus  ^/64  is  the  third  root 
of  64,  that  is,  it  is  4.  If  the  power 
consist  of  several  numbers  or  let- 
ters, they  must  be  connected.  Thus, 
2/4+12,  or  ^(4  +  12),  is  4;  but 
1^/4+12,  without  the  connexion,  is 
14.  For  the  second  root,  or,  as  it  is 
called,  the  square  root,  the  sign  is 
used  without  the  exponent :  as 
^/9=3.    Roots  are  also  expressed  by 


/jJJkMM 


ALK 

fractional  exponents,  over  the  right : 

as  a?  is  the  same  as  \J  a. 
oo  Indefinitude,  denotes  that  the  quan- 
tity before  which  it  is  put,  is  greater 

or  less  than  any  value  that  can  be 

assigned :  as  ^,  or  j. 

A'LGENIB.  A  star  of  the  second 
magnitude,  on  the  right  side  of  Perseus. 

A'LGOL.  Medusa's  Head.  A  variable 
star  in  the  constellation  Perseus. 

A'LGORAB.  A  star  of  the  third  mag- 
nitude, in  the  right  wing  of  Corvus. 

A'LGORITHM.  An  Arabic  term  ex- 
pressing numerical  computation,  and  now 
generally  used  to  denote  the  operative 
part  of  arithmetic  or  of  algebra. 

A'LIFORM  (ala,  a  wing,  forma,  like- 
ness).    Wing-like;  shaped  like  a  wing. 

A'LILACE.  An  Arabic  term  for  the 
index  which  traverses  the  centre  of  an 
astrolabe  or  quadrant,  carrying  the  sights 
or  telescope,  and  indicates  on  the  limb  of 
the  instrument  the  number  of  degrees 
and  minutes  which  an  object  is  elevated 
above  the  horizon. 

A'LIQUOT  PART  {aliquot,  some). 
A  number  which  divides  a  given  num- 
ber without  leaving  a  remainder :  thus, 
2,  4,  5,  and  10  are  aliquot  parts  of  20.  All 
the  aliquot  parts  of  any  number  may  be 
thus  found :— divide  the  given  number 
by  its  least  divisor ;  then  divide  the  quo- 
tient also  by  its  least  divisor;  and  so  on, 
always  dividing  the  last  quotient  by  its 
least  divisor,  till  the  quotient  1  is  ob- 
tained ;  all  the  divisors  thus  taken  are 
the  prime  aliquot  parts  of  the  given 
number. 

ALISMA'CEvE.  The  Water-Plantain 
tribe  of  Monocotyledonous  plants,  named 
from  the  genus  Alisma.  Floating  plants, 
having  leaves  with  parallel  veins ;  petals 
and  sepals  3  ;  stamens  definite  or  indefi- 
nite ;  ovaries  superior ;  fruit  dry,  indehis- 
cent;  seeds  exalbuminous ;  embryo  shaped 
like  a  horse-shoe. 

A'LIZARIN.  A  peculiar  colouring 
principle  obtained  from  madder,  and 
named  from  alizari,  the  commercial 
name  for  madder  in  the  Levant. 

AL'KAHEST.  An  Arabic  term,  de- 
noting the  pretended  universal  solvent 
or  menstruum  of  the  old  chemists. 

ALKALE'SCENT.  A  term  applied  to 
substances  on  which  alkaline  (ammo- 
niacal)  properties  are  beginning  to  be 
developed. 

ALKALI  PRUSSIAN.   Phlogisticated 

alkali.  A  name  formerly  given  to  a  fixed 

alkali,  when  ignited  with  some  animal 

substance,  and  lixiviated.     It  is  found 

17 


ALL 

to  be  in  a  great  measure  saturated  with 
Prussic  acid. 

A'LKALIES  (al,  the  Arabic  definite 
article,  and  kali,  the  name  of  a  plant 
from  which  the  alkali  is  obtained  by 
burning,  and  an  old  name  for  potash). 
A  class  of  bodies,  which  possess  a  strong 
acrid  and  powerfully  caustic  taste,  and 
exercise  a  corrosive  action  upon  all 
animal  matter;  they  turn  the  infusions 
of  blue  vegetable  colours  to  green,  and 
combine  with  the  various  acids,  forming 
an  extensive  class  of  compounds  called 
salts.    There  are  three  alkalies  : 

1.  The  Vegetable,      ror/x,d  alkalies, 

or  Potash,  be^  lefJm,theA 

2.  The  Mineral,      ^  asl>es    of    in,land 

or  Soda,  .and  marine  plants 

^respectively. 

3.  The  Animal,  or  Ammonia,  or  vola- 
tile alkali,  being  raised  by  distillation 
from  hartshorn,  &c. 

ALKALl'METRY  {alkali,  and  fierpov, 
a  measure).  The  method  by  which  the 
value  of  the  alkalies,  or  carbonated  alka- 
lies, is  determined.  By  means  of  an  in- 
strument, called  an  alkalimeter,  the 
quantity  of  alkali  in  a  given  substance  is 
ascertained  by  the  quantity  of  dilute  sul- 
phuric acid  of  a  known  strength  which 
a  certain  weight  of  them  can  neutralize. 

A'LKALINE  AIR.  The  term  by 
which  Priestley  first  described  ammonia, 
or  ammoniacal  gas,  the  volatile  alkali. 

A'LKALINE  EARTHS.  A  term  ap- 
plied to  magnesia,  lime,  baryta,  and 
strontia,  from  their  earthy  character  and 
alkaline  properties. 

ALKALFNITY.  The  property  of  an 
alkali,  viz.  that  of  turning  vegetable 
blues  into  green. 

ALKALIZA'TION.  The  impregna- 
tion of  any  substance  with  an  alkali. 

A'LKALOIDS  {alkali,  eido?,  likeness). 
Vegeto-alkalies.  A  general  term  for  cer- 
tain bodies  containing  nitrogen,  which 
have  the  properties  of  the  basic  or  me- 
tallic oxides,  and  form  salts  with  acids. 
They  are  produced  in  plants  during  vege- 
tation. 

A'LKANET.  A  reddish  purple  dye, 
obtained  fron  the  roots  of  the  Anchusa 
tinctoria. 

A'LKER.  A  star  of  the  third  magni- 
tude in  the  constellation  Crater. 

A'LLAGITE  A  mineral  of  a  brown 
or  green  colour,  consisting  of  a  carbo- 
silicate  of  manganese. 

A'LLANITE.  A  mineral  containing 
cerium,  found  in  Greenland,  and  named 
from  Mr.  Allan. 


ALL 


ALM 


ALLANTOIC  ACID  {allantois,  a 
membrane  situated  between  the  amnion 
and  the  chorion).  A  white  crystallizable 
acid,  described  by  Vauquelin  under  the 
name  of  amniotic  acid,  and  said  to  exist 
in  the  liquor  amnii  of  the  cow.  This 
fluid  contains  a  crystalline  substance 
called  allantoin. 

ALLEGORY  (dW^yopia,  a  descrip- 
tion of  one  thing  under  the  image  of  an- 
other). In  Rhetoric,  a  figurative  repre- 
sentation by  which  some  meaning  is 
signified  beyond  what  is  expressed:  as 
in  the  "  Fairy  Queen"  of  Spenser,  and 
Swift's  "  Tale  of  a  Tub." 

ALLE'GRO.  An  Italian  adjective, 
signifying  gay,  sportive,  and  denoting, 
in  music,  quick  time.  Allegretto  is  a 
diminutive  of  allegro,  and  denotes  a  tune 
rather  quick  and  sportive,  but  less  so 
than  that  indicated  by  the  term  allegro. 

ALLIA'CEOUS  {allium,  garlic).  A 
term  applied  to  any  thing  which  has  the 
odour  of  garlic.  In  botany,  \\  denotes 
plants  which  partake  of  the  properties  of 
garlic  or  of  the  onion. 

ALLIGA'TION  (alligo,  to  bind  toge- 
ther or  unite).  A  rule  in  arithmetic, 
applied  only  in  commerce,  by  which  the 
price  of  a  mixture  is  found,  when  the 
price  of  the  ingredients  is  known.  Me- 
dial alligation  is  the  method  of  finding 
the  rate  or  quality  of  a  compound,  from 
the  given  rates  and  quantities  of  the  in- 
gredients. Alternate  alligation  is  the 
method  of  finding  the  quantities  of  ingre- 
dients necessary  to  form  a  compound  of 
a  given  rate. 

A'LLIOTH.  A  star  of  the  third  mag- 
nitude in  the  tail  of  the  Great  Bear. 

ALLITERATION  (ad,  to,  litera,  a 
letter).  In  composition,  the  frequent 
recurrence  of  the  same  letter  at  the  com- 
mencement of  words,  as  in  the  line  of 
Churchill, 

**  And  apt  alliteration's  artful  aid." 

A'LLOCHRO'ITE  ('d\\o?,  another, 
Xpoa,  colour).  A  mineral  allied  to  the 
garnet,  exhibiting  several  changes  of 
colour,  when  melted  with  phosphate  of 
soda  before  the  blowpipe. 

A'LLOPHANE  (ciWoc,  different,  <pai- 
vofxai,  to  appear).  A  mineral  of  a  blue, 
green,  or  brown  colour,  formerly  called 
Riemannite,  and  found  in  a  bed  of  iron- 
shot  lime-stone  in  Greywacke  slate,  in 
the  forest  of  Thuringia. 

A'LLOTROPIC  STATE  (&XXoc,  an- 
other, TpoiTof,  condition).  A  term  applied 
to  the  dissimilar  condition  observed  in 
certain  elements  of  which  the  various 
18 


forms  of  carbon,  as  diamond,  graphite, 
&c,  afford  a  well-known  example.  This 
is  one  of  the  causes  of  the  isomerism  of 
their  compounds. 

ALLO'XAN;  ALLOXA'NTIN.  Com- 
pounds containing  cyanogen  and  carbonic 
oxide,  and  discovered  in  the  decomposi- 
tion of  uric  acid.  Alloxan  is  another 
name  for  the  erythric  acid  of  Brugna- 
telli.  Alloxanic  acid  is  produced  by  the 
metamorphosis  of  alloxan  by  caustic 
alkalies. 

ALLO'Y  (alloyer,  French,  to  mix  one 
metal  with  another,  for  the  purpose  of 
coinage).  A  natural  or  artificial  com- 
pound of  two  or  more  metals,  as  brass, 
bell-metal,  bronze,  &c.  But  the  term  is 
not  employed  when  mercury  enters  into 
the  compound ;  it  is  then  called  an  amal- 
gam. 

ALLU'VIUM  (alluo,  to  wash  upon). 
A  general  designation  of  earth,  sand, 
gravel,  stones,  and  other  transported 
matter,  which  have  been  washed  away 
and  thrown  down  by  rivers,  floods,  or 
other  causes,  upon  land  not  permanently 
submerged  beneath  the  waters  of  lakes 
and  seas. 

Alluvial  Deposits.  These  are  divided 
by  many  authors  into  two  kinds.  1.  Old 
Alluvium,  or  Diluvium,  which  is  gene- 
rally referred  to  the  tertiary  series,  and 
often  contains  remains  of  animals,  more 
or  less  resembling  those  living  at  the 
present  day.  2.  Recent  Alluvium,  or 
deposits  of  the  same  nature,  but  pro- 
duced by  causes  which  are  in  operation 
at  the  present  day. 

ALMAAC.  A  star  of  the  second  mag- 
nitude in  the  northern  constellation  An- 
dromeda 

ALMACA'NTER.  An  Arabic  term 
formerly  employed  in  astronomy  to  de- 
note a  small  circle  of  the  sphere  parallel 
to  the  horizon.  Two  stars  which  have 
the  same  almacanter,  have  the  same  alti- 
tude, and  hence  the  term  almacanter  sig- 
nifies a  circle  of  altitude,  just  as  a  small 
circle  parallel  to  the  equator,  all  whose 
points  have  therefore  the  same  declina- 
tion, is  called  a  circle  of  declination. 

A'LMANAC.  An  Arabic  term  signi- 
fying reckoning,  and  applied  to  a  calen- 
dar, wherein  the  days  of  the  month,  fes- 
tivals, lunation,  motion  of  the  heavenly 
bodies,  eclipses,  &c,  are  reckoned  for 
each  year.     See  Era. 

A'LMANDINE.  A  designation  of  pre- 
cious or  noble  garnet,  occurring  in  pri- 
mitive rocks  and  primitive  metalliferous 
|  beds,  and  used  for  ring-stones. 


ALT 


ALU 


ALOE'TIC  ACID.  The  bitter  prin- 
ciple of  aloes  ;  a  precipitate  procured  by 
heating  nitric  acid  on  aloes. 

ALPHABET.  A  term  derived  from 
the  first  two  letters  of  the  Greek  lan- 
guage, alpha,  beta,  or  from  the  cor- 
responding Hebrew  letters,  aleph,  beth; 
and  applied  to  the  series  of  letters  used 
in  different  countries.  The  term  corre- 
sponds with  our  familiar  expression,  the 
A,  B,  C ;  and  some  writers  have  assigned 
an  analogous  origin  to  the  Latin  name 
given  to  the  letters,  viz.  elementa,  which 
corresponds  with  the  pronunciation  of 
the  three  liquids,  /,  m,  n. 

ALPHAORCEIN ;  BETAORCEIN. 
Terms  applied  by  Dr.  Kane  to  two  sub- 
stances composing  the  orcein  of  archil : 
the  latter  is  produced  by  oxidation  of  the 
former,  and  is  the  orcein  of  chemists. 

A'LPHERATZ.  A  star  of  the  second 
magnitude  in  the  head  of  Andromeda. 

ALPHO'NSINES.  A  series  of  astro- 
nomical tables  drawn  up  by  order  of 
Alphonso  X.  of  Castile,  in  the  year  1252. 
They  contain  the  places  of  all  the  fixed 
stars,  and  all  the  methods  and  tables 
then  in  use  for  the  computation  of  the 
places  of  the  planets. 

ALPINE  PLANTS.  Plants  which 
grow  naturally  in  mountainous  situa- 
tions, where  they  are  covered  with  snow 
during  the  winter. 

ALSINA'CEjE.  The  Chickweed  tribe 
of  Dicotyledonous  plants.  A  section  of 
the  Caryophyllaceae,  in  which  the  sepals 
are  disunited.     See  Silenacece. 

A'LTAN.  A  star  of  the  first  magni- 
tude in  the  northern  constellation  Aquila, 
the  eagle  with  Antinous. 

ALTERATIVES  {altero,  to  change). 
Remedies  which  produce  a  change.  Re- 
medies which  very  gradually  re-establish 
the  health,  as  a  drop  of  water,  by  fre- 
quently falling,  hollows  a  stone. 

ALTE'RNATE  {alternatus,  changed 
by  turns).  A  term  applied  in  geometry 
to  the  angles  which  are  made  by  two  lines 
with  a  third,  on  opposite  sides  of  it.  In 
algebra,  those  terms  of  a  proportion  are 
said  to  be  alternate,  which  are  separated 
from  one  another  by  another  term :  thus, 
in  the  proportion 

2 : 4 : :  8 :  i6, 

2  and  8  are  alternate  terms,  as  also  are 
4  and  16.  'If  alternate  terms  be  rendered 
consecutive,  and  consecutive  terms  alter- 
nate, the  proportion  is  still  maintained: 
thus, 

2 : 8 : :  4 :  i6.  N 

This  relation  is  referred  to  in  the  fifth 
19 


book  of  Euclid  by  the  Latin  word  alter- 
nando,  which  signifies  "  by  alternation," 
or  alternately. 

1.  Alternate,  in  Botany.  That  position 
of  leaves  upon  the  stem,  in  which  one 
leaf  is  placed  above  or  below  another, 
and  on  the  opposite  side.  The  term  is 
generally  employed  in  distinction  to  oppo- 
site, or  that  arrangement  in  which  two 
leaves  are  developed  from  the  same  plane. 

2.  Alternately  pinnate.  A  term  used 
in  botany,  where  the  leaflets  of  a  pinnate 
leaf  are  placed  alternate^  on  the  common 
petiole,  as  in  potentilla  rupestris. 

ALTHE'INE.  A  supposed  new  vege- 
table principle,  extracted  from  the  roots 
of  althea  officinalis,  and  found  to  be  iden- 
tical with  asparagin. 

ALTHIO'NIC  ACID.  An  acid  found 
in  the  residue  of  the  preparation  of  de- 
fiant gas,  by  means  of  alcohol  and  sul- 
phuric acid,  and  named  from  the  words 
alcohol  and  ethionic. 

A'LTITUDE  (altus,  high).  A  term 
applied  in  Astronomy  to  the  angle  of 
elevation  of  a  celestial  body  above  the 
horizon,  measured  in  the  arc  of  that 
vertical  circle  which  passes  through  the 
body. 

1.  The  apparent  altitude  of  a  star  is 
the  angle  found  by  immediate  observa- 
tion ;  the  real  altitude  is  ascertained  by 
correcting  the  apparent  altitude  for  re- 
fraction, parallax,  &c. 

2.  The  altitude  of  the  pole  is  the  geo- 
graphical latitude  of  the  place  of  observa- 
tion, and  remains  the  same  throughout 
the  twenty-four  hours. 

3.  In  Geometry,  the  term  altitude  is 
synonymous  with  height.  Thus,  the  alti- 
tude of  a  triangle  is  measured  by  the 
straight  line  drawn  from  the  vertex  per- 
pendicular to  the  base ;  that  of  a  cone,  by 
the  straight  line  drawn  from  the  vertex 
perpendicular  to  the  plane  of  the  base ; 
that  of  a  parallelogram,  by  the  perpen- 
dicular drawn  from  its  base  to  the  oppo- 
site side;  that  of  a  prism,  by  the  perpen- 
dicular distance  between  its  bases. 

A'LUDEL.  A  pear-shaped  vessel  re- 
sembling the  alembic,  and  used  by  the 
old  chemists  in  the  process  of  sublima- 
tion. 

A'LULA  (dim.  of  ala,  a  wing).  A 
little  wing. 

A'LUM.  Alumen.  A  salt  consisting 
of  a  ternary  compound  of  alumina,  or 
pure  argillaceous  earth,  potass,  and  sul- 
phuric acid.  Alum  is  the  base  of  pure 
Way.  The  indurated  beds  of  clay  em- 
ployed for  obtaining  the  alum  are  called 


AM  A 


AMB 


alum-stone,  a  siliceous  subsulphate  of 
alumina.  Alum-slate  is  a  rock,  from 
which  alum  is  prepared. 

Rock  alum  is  a  variety  of  alum 
brought  from  Roccha,  formerly  Edessa, 
in  Syria  Roman  alum  is  the  purest 
variety  of  alum,  containing  no  ammonia 
in  its  composition.  Ammonia  alum  is  a 
double  salt,  consisting  of  the  sulphates  of 
ammonia  and  of  alumina.  Soda  alum  is 
a  double  salt,  consisting  of  the  sulphates 
of  alumina  and  of  soda.  Iron  alum, 
manganese  alum,  and  chrome  alum  are 
salts  of  alumina,  to  which  the  generic 
term  alum  is  applied,  their  specific  dif- 
ferences being  denoted  by  the  name  of 
the  metallic  peroxide  which  they  respect- 
ively contain. 

ALU'MINA.  The  earthy  oxide  of 
aluminum ;  a  primitive  earth,  constitut- 
ing the  plastic  principle  of  all  clays,  loams, 
and  boles,  and  her.ce  termed  argil,  or 
argillaceous  earth.  The  name  alumina 
is  derived  from  alumen,  or  alum,  the  salt 
from  which  it  is  generally  obtained  in  a 
pure  state. 

ALU'MINITE.  The  name  by  which 
mineralogists  designate  the  native  hy- 
drated  subsulphate  of  alumina. 

ALU'MINUM.  A  metallic  substance 
resembling  platinum,  constituting  the 
base  of  alumina,  and  obtained  from  its 
chloride  by  the  action  of  potassium. 

ALUTA'CEOUS  {aluta,  tanned  leather). 
Of  a  pale  brown  colour,  like  that  of  tanned 
leather. 

A'LVEOLATE  {alveolus,  a  socket  or 
cavity).  A  term  applied  in  Botany  to  a 
surface  covered  with  cavities,  as  the 
receptacle  of  some  species  of  the  Com- 
positae. 

A'MADOU.  A  variety  of  the  boletus 
igniarius,  found  on  old  ash  and  other 
trees.  By  means  of  nitre  it  is  converted 
into  German  tinder. 

AMA'LGAM  (a/j.a,  together,  yafiea), 
to  unite).  A  compound  of  mercury  with 
other  metals.  A  native  amalgam,  which 
is  of  silver,  occurs  in  Hungary  and  Swe- 
den, in  various  forms.  The  amalgam 
employed  in  electrical  apparatus  con- 
sists of  one  part  of  tin,  two  of  zinc, 
and  six  of  mercury,  mixed  with  some 
unctuous  matter,  and  spread  on  silk  or 
leather. 

AMALGAMATION.  The  process  of 
making  an  amalgam,  or  mixture  of  mer- 
cury with  some  other  metal,  for  the  pur- 
pose of  separating  silver  and  gold  from 
their  ores.  The  operation  is  founded  on 
the  property  which  mercury  possesses  of 
20 


dissolving  these  metals  out  of  the  mine- 
rals with  which  they  are  associated. 

AMARANTA'CE^E.  The  Amaranth 
tribe  of  Dicotyledonous  plants.  Herbs 
or  shrubs,  with  leaves  simple,  exstipu- 
late  ;  flowers  in  heads  or  spikes ;  stamens 
hypogynous  ;  ovary  superior ;  fruit  a 
utricle ;  seeds  lentiform,  with  farinaceous 
albumen  ;  embryo  curved  round  the  cir- 
cumference. 

AMARYLLIDA'CE^E.  The  Narcissus 
tribe  of  Monocotyledonous  plants.  Gene- 
rally bulbous,  sometimes  fibrous-rooted, 
occasionally  with  a  lofty  stem.  Leaves 
ensiform ;  calyx  and  corolla  equally 
coloured,  superior;  stamens  6;  anthers 
bursting  inwardly  ;  stigma  3-lobed  ;  albu- 
men fleshy  or  horny. 

AMA'RYTHRIN  (amarus,  bitter,  ery- 
thrin).  A  bitter  extractive  matter  pro- 
cured from  erythrin,  sometimes  termed 
erythrin  bitter. 

AMAZO'NIAN  STONE.  A  beautiful 
green  felspar,  occurring  in  rolled  masses 
near  the  Amazon  river. 

A'MBER.  Succinum.  A  hard,  brittle, 
transparent  or  opaque  substance,  of  an 
orange  colour,  considered  to  be  an  indu- 
rated vegetable  juice,  or  concreted  balsam. 
By  destructive  distillation  of  this  sub- 
stance, a  light  yellow  sublimate  is  pro- 
cured, called  amber  camphor,  or  volatile 
resin  of  amber. 

A'MBERGRIS  (ambre  gris,  grey  am- 
ber). A  sebaceous  substance  supposed 
to  be  formed  in  the  intestines  of  the 
physeter  macrocephalus,  or  spermaceti 
whale,  and  sometimes  found  floating  in 
the  sea,  or  thrown  upon  the  shore.  The 
Japanese  call  it  whale's  dung. 

A'MBITUS  (ambio,  to  encompass). 
The  circumference,  or  bounding  line,  of 
a  surface,  as  of  a  leaf. 

AMBLY'GONITE.  A  rare  mineral, 
consisting  of  a  phosphate  of  alumina 
and  lithia,  and  occurring  in  granite,  in 
Saxony.  It  appears  to  be  a  species  of 
spodumene. 

A'MBREIN.  A  peculiar  substance 
obtained  by  digesting  ambergris  in  hot 
alcohol.  By  absorption  of  oxygen  it  is 
converted  into  an  acid  called  ambreic 
acid. 

AMBULA'CRA  (ambulacrum,  an  al- 
ley). The  narrow  longitudinal  portions 
of  the  shell  of  the  echinus,  or  sea-urchin, 
which  are  perforated  by  small  orifices, 
traversed  by  tentacular  suckers,  and 
alternated  with  the  broad  tuberculate 
spine-bearing  portions. 

A'MBULATORY  {ambulo,  to  walk). 


AMI 


AMN 


Formed  for  walking ;  as  applied  to  the 
feet  of  those  birds  in  which  the  toes  are 
placed  three  before  and  one  behind. 
Such  birds  were  called  by  Illiger  ambu- 
latores. 

AME'NTUM.  A  catkin;  a  form  of 
inflorescence,  in  which  the  flowers  of  a 
spike  are  destitute  of  calyx  and  corolla, 
the  place  of  which  is  occupied  by  bracts, 
and  the  whole  inflorescence  falls  off  in  a 
single  piece,  either  after  flowering  or  the 
ripening  of  the  fruit,  as  in  the  hazel  and 
the  willow.  Plants  which  have  this  kind 
of  inflorescence  were  formerly  called 
amentaceous. 

AME'RICAN  RACE.  One  of  the  five 
principal  varieties  of  mankind,  originally 
spread  over  the  whole  of  the  Americas, 
south  of  the  sixtieth  degree  of  north  lati- 
tude. This  variety  is  characterized  by  a 
reddish-brown  complexion,  long  black 
lank  hair,  deficient  beard,  eyes  black 
and  deep-set,  receding  brow,  cheek- 
bones prominent,  but  more  arched  and 
rounded  than  in  the  skull  of  the 
Mongolian,  aquiline  nose,  small  skull, 
with  the  apex  high  and  the  back  part 
flat,  large  mouth,  and  tumid  lips,  with 
fine  symmetrical  frames  of  middle 
height. 

AMETA'BOLA  (a,  priv.,  ne-raftoX^, 
change).  A  term  applied  by  zoological 
writers  to  those  genera  of  insects  which 
do  not  undergo  metamorphoses;  which 
escape  from  the  egg  nearly  under  the 
same  form  as  they  preserve  through  life, 
and  which,  on  reaching  their  perfect 
state,  do  not  acquire  wings.  See  Meta- 
bola. 

A'METHYST  (a,  priv.,  ^ed'ro,  to  be 
intoxicated).  The  oriental  amethyst  is 
a  rare  violet-coloured  gem,  called  corun- 
dum, or  adamantine  spar,  with  the  qua- 
lities of  the  sapphire  or  ruby.  The  occi- 
dental or  common  amethyst  is  merely 
a  coloured  crystal  or  quartz.  The  name 
is  derived  from  its  reputed  virtue  of  pre- 
venting intoxication. 

AMIA'NTHOIDE.  A  flexible,  fila- 
mentous mineral,  of  an  olive  green 
colour,  found  at  Oisans  in  France. 

AMIA'NTHUS  (a,  priv.,  fuaitm,  to 
corrupt).  Mountain  flax.  An  incom- 
bustible mineral,  consisting  of  very  deli- 
cate and  regular  silky  fibres.  The  term 
appears  to  have  been  derived  from  the 
circumstance  that  soiled  cloths,  made 
of  this  substance,  are  better  cleansed  by 
being  thrown  into  the  fire,  than  by  wash- 
ing.    See  Asbestos. 

A'MIATITE.    Fiorite,  or  pearl-sinter ; 
21 


a  volcanic  production,  chiefly  silica,  in  a 
stalactitical  form. 

A'MIDES.  A  series  of  saline  com- 
pounds, in  which  the  compound  of  nitro- 
gen and  hydrogen  occurs,  containing  an 
atom  less  of  hydrogen  than  ammonia. 
The  term  amidogen  has  been  applied  to 
their  radical. 

A'MIDIN  (amidon,  starch).  Gelati- 
nous starch  ;  the  soluble  part  of  starch ; 
a  substance  intermediate  between  gum 
and  starch. 

A'MILENE.  A  liquid  hydrocarbon, 
obtained  by  distilling  hydrate  of  oxide  of 
amyl  repeatedly  with  anhydrous  phos- 
phoric acid. 

A'MMELIDE:  A'MMELINE.  Two 
of  the  products  of  the  decomposition  of 
sulpho-cyanogen.     See  Melam. 

AMMO'NIA.  Ammoniacal  Gas.  A 
transparent,  pungent  gas,  formed  by  the 
union  of  nitrogen  and  hydrogen,  and 
named  from  the  substance  sal  ammoniac, 
of  which  it  constitutes  the  basis.  It  has 
also  been  termed  alkaline  air,  and  the 
volatile  alkali. 

AMMONI'ACAL  AMALGAM.  A  sub- 
stance formed  by  the  action  of  galvanism 
on  a  salt  of  ammonia,  in  contact  with  a 
globule  of  mercury. 

AMMONI'ACO.  A  term  prefixed  to 
the  names  of  salts,  in  which  ammonia 
has  been  added  in  sufficient  quantity  to 
combine  with  both  the  acid  and  the  base. 
A'MMONITE.  An  extinct  and  very 
numerous  genus  of  molluscous  animals, 
called  Cephalopoda,  allied  to  the  modern 
genus  Nautilus,  which  inhabited  a  cham- 
bered shell,  curved  like  a  coiled  snake. 
Species  of  it  are  found  in  all  geological 
periods  of  the  secondary  strata ;  but  they 
have  not  been  found  in  the  tertiary  beds. 
From  its  resemblance  to  the  horns  of  the 
statues  of  Jupiter  Ammon,  it  is  called 
cornu  Ammonis;  from  its  coiled  form,  it 
is  popularly  called  snake-stone. 

AMMO'NIUM.  A  hypothetical  com- 
pound of  nitrogen  and  hydrogen.  It  is 
not  an  elementary  body,  and  possibly  not 
even  a  metal.  Berzelius,  however,  con- 
sidered it  the  metallic  base  of  ammonia. 
AMMONIU'RET.  A  compound  con- 
taining ammonia  and  a  salifiable  base,  or 
other  substance  not  acid. 

A'MNIOS.  In  Botany,  a  gelatinous 
substance,  in  which  the  embryo  of  a  seed 
is  at  first  suspended.  It  is  subsequently 
absorbed,  or  solidified  in  the  form  of 
albumen. 

AMNIOTIC  ACID.  An  acid  supposed 
to  be  found  in  the  liquor  amnii  of  the 


AMP 


AMP 


cow,  but  actually  belonging  to  the  liquor 
of  the  allantois. 

AMO'RPHOUS  (a,  priv.,/iop0»/,form). 
Shapeless,  irregular  ;  a  term  applied  to 
mineral  and  other  substances  which  oc- 
cur in  forms  not  easy  to  be  defined. 

AMO'KPHOZO'A  (anopcpo?,  shapeless, 
£wov,  animal).  Shapeless  animals ;  a  term 
applied  by  Blainville  to  the  Porifera  of 
other  writers,  including  the  sponges. 

A'MPELIC  ACID.  An  acid  obtained 
from  the  oils  of  bituminous  schist.  The 
term  ampelin  denotes  an  oily  matter  pre- 
pared from  the  same  substance. 

AMPE'LID^E  {ampelis,  the  chatterer). 
Chatterers;  a  family  of  the  Insessores, 
or  perching  birds,  or  the  Cantatrices  of 
Macgillivray,  distinguished  by  the  enor- 
mous width  of  their  gape,  which  in  many 
extends  beyond  the  eye,  and  in  some  is 
nearly  as  wide  as  in  the  goatsucker. 
They  belong,  generally,  to  tropical  Ame- 
rica ;  only  one,  the  waxwing,  is  found  in 
Europe.     See  Dentirostres. 

A'MPELITE  (ci^TreAo?,  a  vine).  A 
kind  of  slate,  found  in  the  fossililerous 
and  in  the  metamorphic  series  of  rocks. 
The  aluminous  variety  is  the  alum  slate ; 
the  graphic,  the  graphic  slate. 

AMPERE'S  THEORY.  An  electro- 
dynamic  theory,  by  which  the  mutual 
attraction  or  repulsion  of  two  magnets  is 
referred  to  the  mutual  action  of  electric 
currents,  according  to  a  certain  funda- 
mental law,  in  a  manner  resembling 
the  polar  attraction  of  statical  electricity, 
i.  e.  of  electricity  in  a  state  of  tension. 
In  following  out  this  theory,  it  was  sup- 
posed by  Ampere,  that  around  each  par- 
ticle of  a  body,  which  has  been  consti- 
tuted a  magnet,  there  is  constantly  cir- 
culating, in  a  certain  stated  direction,  a 
small  current  of  electric  fluid. 

A'MPHI-;  A'MPHIS-  (dufl,  d/x^i'O. 
The  former  of  these  prefixes  is  a  Greek 
preposition,  signifying  on  both  sides, 
around,  that  which  may  be  understood  in 
two  ways.  The  latter  prefix  has  strictly 
the  same  meanings,  but  is  mostly  used 
as  an  adverb. 

1.  Amphi-bia  (plot,  life).  The  second 
class  of  the  Vertebrata,  comprising  ani- 
mals which  commence  their  larva  state 
as  fishes,  and  undergo  various  stages  of 
metamorphosis  in  advancing  towards  the 
condition  of  reptiles,  their  most  striking 
peculiarity  consisting  in  the  change  from 
aquatic  respiration  by  branchiae  to  an 
atmospheric  respiration  by  true  lungs, 
They  are  consequently  designated  as  ani- 
mals having  a  double  life. 
22 


2.  Amphi-bole.  A  silicate  of  lime  and 
magnesia,  otherwise  called  hornblende. 
The  derivation  of  this  term  is,  perhaps, 

4upl/3o\os,  equivocal,  from  the  liability 
of  this  mineral  to  be  mistaken  for  augite, 
which  is  similarly  constituted. 

3.  Amphi-bolia  (dfi<pl(3o\os,  equivocal). 
The  "fallacia  amphiboliae"  of  logicians 
is  seen  in  those  amphibolous  sentences 
which  are  capable  of  two  meanings,  not 
from  the  double  sense  of  any  of  the  words, 
but  from  their  admitting  of  a  double 
construction,  as  in  the  witch-prophecy  of 
Shakspere,  "The  duke  yet  lives  that 
Henry  shall  depose."  This  is  what  the 
French  call  "  construction  louche,"  a 
squinting  construction;  i.  e.  where  some 
word  or  words  may  be  referred  either  to 
the  former  or  latter  clause  of  the  sen- 
tence. 

4.  Amphi-bolites.  Trap-rocks,  the  basis 
of  which  is  amphibole  or  hornblende,  a 
silicate  of  lime  and  magnesia.  The  deri- 
vation is  the  same  as  that  of  amphibole. 

5.  Amphi-gamous  (yd/jLos,  nuptials).  A 
term  applied  by  De  Candolle  to  those 
cellular  cryptogamous  plants,  which  have 
no  trace  whatever  of  sexual  organs,  as 
distinguished  from  the  other  cryptoga- 
mous plants,  which,  from  the  unusual 
character  of  their  fructification,  are  called 
cetheogamous. 

6.  Amphi-gen  (jevos,  a  kind).  A  double 
silicate  of  potash  and  alumina,  other- 
wise called  leucite  or  Vesuvian.  The 
name  appears  to  be  derived  from  its  com- 
position, the  oxygen  of  the  silica  being 
equal  to  that  of  the  bases. 

7.  Amphi-pneurta  (irveut,  to  breathe). 
An  order  of  amphibious  animals,  includ- 
ing the  proteus  and  the  siren,  which  re- 
tain their  gills  during  life,  and  acquire 
lungs  in  addition  by  the  partial  meta- 
morphosis which  they  undergo. 

8.  Amphi-poda  (irovs,  nodos,  a  foot). 
A  group  of  crustaceous  animals,  which 
have  feet  for  both  walking  and  swimming. 
The  best  known  British  species  is  the 
sand-hopper,  which  burrows  in  the  sand, 
and  which,  unlike  most  of  the  group, 
seldom  enters  the  water. 

9.  Amphi-sarca  [a «p£,  <rapKor,  flesh).  In 
botany,  a  compound  fruit,  many-celled, 
many-seeded,  superior,  indehiscent;  in- 
durated or  woody  externally,  pulpy  inter- 
nally, as  in  adansonia. 

10.  Amphis-btenidce  (ftalvta,  to  walk). 
Double-walkers  ;  a  small  family  of  Ophi- 
dian reptiles,  intermediate  in  some  re- 
spects between  the  true  serpents  and  the 

I  slow-worms.    They  derive    their    name 


AMY 


ANA 


from  their  power  of  moving  either  back- 
wards or  forwards  with  equal  facility. 
The  group  is  restricted  to  the  warmest 
parts  of  South  America. 

11.  Amphi-scians  {ama,  shadow).  A 
designation  of  the  people  who  inhabit  the 
torrid  zone,  and  are  so  called  because 
they  have  their  shadows  at  noon  turned 
sometimes  one  way,  sometimes  another, 
or  north  and  south — that  is,  to  the  north, 
when  the  sun  at  noon  is  to  the  south  of 
their  zenith,  and  vice  versa. 

12.  Amphi-spermium  (a-7r«?p^.a,  seed).  A 
term  applied  by  Link  to  a  pericarp  which 
is  of  the  same  figure  as  the  seed  it  con- 
tains. 

13.  Amphi-stoma  (oro/ia,  the  mouth). 
A  genus  of  suctorial  parasitic  worms, 
which  have  pores,  like  mouths,  at  both 
ends  of  the  body. 

14.  Amphi-tropal  (tpotto?,  a  turn).  That 
which  is  curved  round  the  body  to  which 
it  belongs ;  a  term  applied  to  tlie  embryo 
of  the  seed,  when  curved  round  the  al- 
bumen, so  that  its  two  ends  are  presented 
to  the  same  point. 

15.  Amphi-tropous  (tpotto?,  a  turn).  A 
term  applied  to  the  ovule  of  plants,  when 
the  foraminal  and  chalazal  ends  are 
transverse  with  respect  to  the  hilum. 

AMPLE'XICAUL  {amplector,  to  em- 
brace, caulis,  a  stem).  Stem-embracing; 
as  applied  to  leaves  which  sheathe  the 
stem,  as  in  many  ranunculaceous  plants. 

A'MPLITUDE  {amplus,  large).  A 
term  applied,  in  astronomy,  to  the  angu- 
lar distance  of  a  celestial  body,  at  the 
time  when  it  rises  or  sets,  from  the 
east  or  west  point  of  the  horizon.  The 
amplitude  is  measured  by  the  arc  of  the 
horizon  intercepted  between  the  east  or 
west  point,  and  the  centre  of  the  celes- 
«  tial  body,  at  the  period  of  its  rising  or 
setting  on  any  particular  day.  See 
Horizon. 

Amplitude  magnetic.  A  term  applied 
to  the  distances  of  the  points  of  rising  or 
setting,  from  the  east  or  west,  as  shown 
by  the  compass. 

AMPULLA'RINTE.  Apple-snails;  a 
sub-family  of  the  Turbidce,  named  from 
the  genus  ampullaria :  these  animals 
have  a  respiratory  siphon ;  the  shell  is 
globular  or  turbinate. 

AMY'GDALE.E  (duvyidXa,  an  al- 
mond). The  almond  tribe  of  Dicotyledon- 
ous plants,  a  sub-order  of  the  Rosacese. 
Trees  or  shrubs  with  leaves  alternate ; 
corolla  polypetalous ;  stamens  perigynous ; 
ovary  superior,  solitary,  simple ;  fruit 
drupaceous. 
23 


AMY'GDALIN  {duvyddXa,  an  almond). 
A  principle  found  in  the  bitter  almond 
and  the  berries  of  the  cherry-laurel.  By 
the  action  of  alkalies  on  amygdalin,  an 
acid  is  obtained  called  amygdalic  acid. 

AMY'GDALOID  {d/jivyddXa,  an  al- 
mond, et(3o?,  likeness).  One  of  the  forms 
of  the  Trap-rocks,  in  which  agates  and 
simple  minerals  appear  to  be  scattered, 
like  almonds  in  a  cake.  Such  rocks  are 
termed  amygdaloidal  claystone,  amygda- 
loidal  felspar,  &c.  Also,  a  compound 
mineral,  consisting  of  lithomarge,  green 
earth,  calc  spar,  steatite,  and  sometimes 
hornblende,  imbedded  in  greenstone  or 
wacke. 

A'MYL  (anvXov,  fine  meal,  vXt],  matter 
or  principle).  The  hypothetical  radical 
of  a  series  of  amylaceous  compounds, 
generally  considered  as  an  alcohol,  from 
the  analogy  which  exists  between  oil  of 
potatoes,  or  hydrate  of  oxide  of  amyl,  and 
ordinary  alcohol. 

A'MYLIC  ACID  {amylum,  starch). 
A  volatile  acid,  procured  by  digesting 
moistened  starch  with  peroxide  of  man- 
ganese. 

AMYRIDA'CEiE.  An  order  of  fra- 
grant Dicotyledonous  plants,  named  from 
the  genus  Amyris.  Trees  or  shrubs,  with 
leaves  compound,  with  pellucid  dots ; 
corolla  polypetalous ;  stamens  hypogy- 
nous  ;  ovary  superior  ;  fruit  sub-drupa- 
ceous, samaroid,  or  leguminous. 

ANACARDIA'CE,E.  The  Cashew 
tribe  of  Dicotyledonous  plants,  abound- 
ing in  a  resinous,  sometimes  acrid,  highly 
poisonous  juice.  Trees  or  shrubs  with 
leaves  alternate;  flowers  usually  uni- 
sexual ;  stamens  perigynous  ;  ovary  su- 
perior ;  fruit  generally  drupaceous. 

ANACOLU'THON  ( uvaKoXovOeco, 
not  to  follow).  A  grammatical  term, 
denoting  a  want  of  sequence  in  the 
parts  of  a  sentence.  It  occurs  when  the 
latter  part  of  a  sentence  does  not  agree  in 
syntax  with  the  former,  which  sometimes 
happens  when  a  parenthetical  clause  has 
intervened,  so  that  the  author  has  lost 
sight  of  the  construction  with  which  he 
set  out. 

ANAI'MA  (a  priv.,  al/xa,  blood).  The 
name  by  which  Aristotle  designated 
those  animals  which  have  no  red  blood, 
and  which  he  therefore  supposed  to  be 
without  blood. 

ANA'LCIME.  A  simple  mineral  of 
the  Zeolite  family,  also  called  cubizite, 
of  frequent  occurrence  in  the  trap-rocks. 
It  is  found  in  grouped  crystals  deposited 
by  water,  in  the  fissures  of  hard  lavas. 


ANA 


ANA 


In  chemical  language,  it  is  the  soda  sili- 
cate proportionate  to  amphigen. 

ANALE'MMA  {dvaKnuna,  a  pedestal 
for  a  sun-dial).  A  projection  of  the  sphere 
on  the  plane  of  the  meridian,  made  by 
straight  lines  and  ellipses,  the  eye  being 
supposed  at  an  infinite  distance,  and  in 
the  east  and  west  points  of  the  horizon. 
Also,  an  instrument  of  brass  or  wood,  on 
which  the  projection  is  made  (the  plane 
of  projection  being  the  solstitial  colure), 
with  a  moveable  horizon  attached  to  it. 

ANALE'PTICS  (dvaXan^dvu,  to  re- 
store). Restoratives  ;  tonic  remedies  for 
restoring  the  health,  when  it  has  been 
impaired  by  disease  or  other  causes. 

ANA'LOGOUS  NOUN  (dvd\oyo?t  ac- 
cording to  rule).  A  logical  term,  applied 
to  a  noun  which  has  only  one  significa- 
tion, but  admits  of  being  applied  in  a 
modified  or  subordinate  sense,  to  objects 
which  bear  no  more  than  an  analogy  or 
similarity  to  its  original  signification  :  as 
the  noun  sting— of  an  animal— of  con- 
science— of  an  epigram. 

A'NALOGUE  {dvdXoyos,  according  to 
rule).  A  body  which  resembles  or  cor- 
responds with  another  body :  a  recent 
shell  of  the  same  species,  as  a  fossil  shell 
is  the  analogue  of  the  latter.  A  part  or 
organ  in  one  animal  which  has  the  same 
function,  as  another  part  or  organ  in  a 
different  animal  is  an  analogue  of  the 
latter.     See  Homologue. 

ANA'LOGY  (uvdAoYoc,  according  to 
rule).  A  term  denoting,  in  common  ac- 
ceptation, an  imperfect  degree  of  resem- 
blance between  different  objects.  In 
Geometry  it  signifies  proportion,  simili- 
tude, or  equality  of  ratios  or  relations. 
In  Zoology  it  indicates  the  relation  which 
animals  bear  to  one  another  in  conse- 
quence of  their  resemblance  in  the  early 
period  of  development,  or  in  the  less  pro- 
portion of  their  organization,  and  must 
not  be  confounded  with  affinity :  thus,  a 
whale  is  analogous  to  a  fish,  from  its 
general  resemblance  and  its  habitation, 
but  it  belongs  to  the  class  Mammalia, 
which  includes  no  fishes. 

ANA'LYSIS  (dvaXum,  to  resolve).  A 
method  of  instruction,  which  begins  with 
those  objects  which  are  most  known ; 
examines  their  properties  and  relations  ; 
compares  them  together;  traces  back 
effects  to  causes ;  and  thus  proceeds  by  a 
path  opposite  to  the  course  of  nature, 
until  it  arrives  at  general  principles  and 
laws.  This  is  the  process  of  induction. 
The  synthetic  method  is  the  reverse  of 
the  analytic,  as  it  proceeds  from  general 
24 


to  subordinate  truths,  from  universals  to 
particulars,  from  causes  to  effects. 

1.  Geometrical  Analysis  is  defined  by 
Pappus,  as  "  the  course  which,  setting 
out  from  the  thing  sought,  and  which  for 
the  moment  is  taken  for  granted,  con- 
ducts by  a  series  of  consequences  to 
something  already  known,  or  placed 
among  the  number  of  principles  admitted 
to  be  true.  By  this  method,  therefore, 
we  ascend  from  a  truth  or  a  proposition 
to  its  antecedents  ;  and  we  call  it  analy- 
sis, or  resolution,  as  if  indicating  an 
inverted  solution.  In  synthesis,  on  the 
contrary,  we  set  out  from  the  proposition 
which  is  the  last  in  the  analysis,  and 
proceed  by  arranging,  according  to  their 
nature,  the  antecedents  which  present 
themselves  as  consequents  in  the  ana- 
lytic method,  and  combining  them  to- 
gether till  we  arrive  at  the  conclusion 
sought." 

2.  Chemical  Analysis.  The  resolution  of 
compounds  into  their  elementary  parts. 
When  merely  the  number  and  nature  of 
these  are  ascertained,  it  is  termed  quali- 
tative analysis ;  when  their  proportions 
also  are  determined,  the  analysis  is  quan- 
titative. Every  distinct  compound,  which 
exists  really  formed,  is  called  a  proxi- 
mate or  immediate  principle,  and  the  pro- 
cess of  procuring  it  is  termed  proximate 
analysis.  The  reduction  of  the  proxi- 
mate principles  into  their  simplest  parts 
constitutes  ultimate  analysis.  Lee  Syn- 
thesis. 

ANAMORPHO'SIS  (dvd,  again,  n6p- 
0axrtf,  formation).  A  distorted  repre- 
sentation of  an  object,  which  is  capable, 
however,  of  assuming  its  proper  appear- 
ance, when  viewed  in  a  particular  direc- 
tion or  through  a  particular  medium. 
The  figure  is  also  restored,  in  some* 
cases,  by  causing  the  anamorphosis  to  be 
reflected  from  specula  with  certain  sur- 
faces, as  those  of  cones  and  cylinders. 
The  term  catoptric  anamorphosis  is  ap- 
plied to  a  drawing  which  has  been  dis- 
torted according  to  regular  laws,  in  order 
to  produce  this  effect ;  and  also  to  its  re- 
flected image  in  a  cylindrical  or  conical 
mirror. 

ANASTATIC  PRINTING  {ixv'una- 
fiai,  to  rise  up).  A  recently  invented 
process  for  copying  from  a  printed  page 
of  any  size,  from  a  line  engraving,  or 
from  any  other  print,  founded  on  the  re- 
pulsion of  dissimilar,  and  the  mutual 
attraction  of  similar,  particles,  as  exhi- 
bited by  water,  oil,  and  gum  arabic.  The 
term  is  derived  from  the  technical  ex- 


ANC 


ANF 


pression  of  setting  off,  applied  to  that 
part  of  the  process  by  which  a  slight  film 
of  ink  is  communicated  by  the  copy  to  a 
zinc  plate. 

ANA'STOMOSE  (ui/ci,  through,  arofxa, 
the  mouth).  A  term  denoting  that  the 
mouths  of  two  vessels  come  into  contact 
and  blend  together,  or  that  two  vessels 
unite  as  if  such  kind  of  union  had  taken 
place. 

A'NATASE.  A  pure  oxide  of  tita- 
nium, having  the  property  of  exhibiting 
various  colours  by  reflected  light,  from 
indigo  blue  to  reddish-brown.  It  occurs 
in  granite,  gneiss,  mica  slate,  and  transi- 
tion limestone. 

ANA'TID^E.  The  Duck  tribe;  a 
family  of  the  Natatores,  distinguished 
by  a  thick  bill,  wrhich  is  horny  only  at  its 
extremity ;  the  remainder  of  the  man- 
dibles being  invested  with  a  soft  skin, 
which  in  other  birds  is  found  only  at 
their  hinder  part.  Under  the  general 
designation  of  ducks,  geese,  and  swans, 
all  the  birds  of  this  family  may  be  ar- 
ranged. 

ANATFFIDA.  An  order  of  Cirrho- 
pods,  named  from  the  genus  anatifa,  and 
characterized  by  the  peduncle  by  which 
the  animal  is  attached  to  its  shell.  See 
Cirrhopoda. 

ANATOMICAL  SYPHON.  An  ap- 
paratus invented  by  Wolf,  for  the  pur- 
pose of  illustrating  the  exertion  of  a  very 
great  pressure,  by  means  of  a  small  quan- 
tity of  liquid. 

ANATOMY  (dva,  through,  tf/xvoj,  to 
cut).  A  term  simply  meaning  dissection, 
but  generally  applied  to  the  whole  science 
of  organization — the  science  whose  object 
is  the  examination  of  the  organs  or  in- 
struments of  life.  Animal  anatomy  is 
•  distinguished  into  human  anatomy  and 
comparative  anatomy,  according  as  it 
treats  of  the  organization  of  the  human 
body,  or  of  that  of  other  animals. 

ANA'TROPOUS  (di/aTp<?7ra>,  to  turn 
upside  down).  Inverted;  turned  entirely 
over  ;  a  term  applied  to  the  condition  of 
ovules  in  many  plants,  as  in  the  apple. 
The  inversion  is  occasioned  by  the  con- 
tinued growth  of  only  one  side  of  the 
ovule,  until  that  portion  of  it  which  was 
originally  near  the  apex  is  brought  down 
to  the  hilum ;  the  base  of  the  nucleus 
is  then  at  the  apex  of  the  ovule. 

ANCELLA'RIN^.  An  aberrant  sub- 
family of  the  Volutidce,  or  volutes,  named 
from  the  genus  ancellaria,  having  the 
aperture  wide,  and  the  base  of  the  pillar 
alone  thickened  and  striated. 
25 


ANDALU'SITE.  A  massive  mineral, 
of  a  red  colour,  first  found  in  Andalusia 
in  Spain. 

ANDA'NTE  (andare,  Ital.,  to  go).  A 
term  employed  in  Music,  to  denote  a 
medium  movement  between  the  extremes 
of  slow  and  quick.     See  Adagio. 

ANDR^EA'CEiE.  An  order  of  Cryp- 
togamous  plants,  named  from  the  genus 
Andrsea.  Branching  moss-like  plants, 
having  a  four-valved  theca,  without  oper- 
culum or  peristome. 

ANDRE'OLITE.  A  mineral  first 
found  at  Andreasberg,  in  the  Hartz  ;  also 
called  harmotone,  and,  from  the  form  of 
its  crystals,  cross-stone. 

ANDROCE'UM  (u'i%>>  a  man,  olnot,  a 
house).  A  term  applied  to  the  male  ap- 
paratus in  plants,  commonly  called  the 
stamens — the  apices  of  old  botanists. 

ANDRO'GYNOUS  {wnp,  a  man,  <ytm/, 
a  woman).  A  term  applied  to  a  herma- 
phrodite, or  animal  which  possesses  the 
generative  organs  of  both  sexes. 

ANDRO'MEDA.  A  northern  constel- 
lation, so  called  by  the  Greeks  from 
Andromeda,  the  daughter  of  Cepheus. 
It  contains  sixty-six  stars. 

ANDRO'PHORUM  (avtjp,  a  man, 
<}){pa>,  to  bear).  A  term  applied  in 
Botany,  by  Mirbel,  to  the  tube  formed 
by  the  union  of  the  filaments  in  a  mon- 
adelphous  combination,  as  in  passiflora. 
ANEMO'METER  (ai/e/uof,  the  wind, 
nerpov,  a  measure).  An  apparatus  for 
measuring  the  force  of  the  wind,  and  in- 
dicating its  direction  at  every  minute  of 
the  day.  An  exterior  vane  is  connected 
with  an  index,  which  traverses  a  sheet  of 
paper  in  a  room  beneath.  The  index 
being  influenced  by  the  movements  of  a 
clock,  and  the  paper  being  marked  into 
divisions  for  every  hour  of  the  day,  an 
accurate  record  is  effected 

A'NEMOSCOPE  (aveixo?,  the  wind, 
a-icoTreu},  to  examine).  An  instrument 
for  determining  the  direction  of  the  wind, 
and  so  constructed  that  the  spindle  of  a 
weathercock  is  connected  with  the  hand 
of  a  dial  on  which  the  points  of  the  com- 
pass are  marked. 

ANE'NTEROUS  (a,  priv.,  evrepa, 
bowels).  A  term  applied  to  the  infuso- 
rial animalcules,  which  have  no  intestinal 
canal. 

ANFRA'CTUOUS  {anfractus,  a  wind- 
ing backward  and  forward).  Spiral ;  re- 
sembling in  direction  the  spire  of  a  cork- 
screw, as  applied  in  Botany  to  the  direc- 
tion of  a  stem  ;  or  folded  back  upon  itself, 
as  the  anther  of  cucumis. 

C 


AN  G 


ANG 


ANGEI'OCARPOUS  (dyyelov,  a  ves- 
sel, Kdpiros,  fruit).  A  term  applied  by 
Mirbel,  in  Carpology,  to  those  plants 
which  have  their  fruit  seated  in  enve- 
lopes not  forming  part  of  the  calyx :  as 
the  filbert,  which  is  enveloped  in  a  husk; 
the  acorn,  which  is  seated  in  a  cupula. 

ANGEI'OSFE'RMIA  {dyyelov,  a  ves- 
sel, cnripua,  seed).  A  term  applied  to 
all  those  plants  which  have  their  seeds 
enclosed  in  a  vessel,  or  pericarp,  as  dis- 
tinguished from  those  which  have  no 
such  protection,  and  are  termed  gymno- 
spermia.  Thus,  the  leguminosa;  are 
angeiospermous,  the  coniferae  gymno- 
spermous. 

A'NGLE  (angulus,  a  corner).  A  plane 
angle,  according  to  Euclid,  is  "  the  in- 
clination of  two  lines  to  one  another, 
which  meet  together,  but  are  not  in  the 
same  direction."  The  point  at  which 
they  meet  is  called  the  vertex  of  the 
angle ;  and  the  angle,  there  formed,  is 
greater  or  less,  according  as  the  lines 
torming  it  diverge  more  or  less  from  each 
other. 

I.  In  Mathematics. 

1.  A  Right  Angle  is  formed  when  one 
straight  line  meets  another  straight  line 
perpendicularly,  and  it  contains  90  de- 
grees, or  the  quarter  part  of  a  circle.  An 
obtuse  angle  is  that  which  is  greater  than 
a  right  angle ;  an  acute  angle,  that  which 
is  less  than  a  right  angle. 

2.  Angle,  Spherical.  In  Trigonometry, 
the  angle  formed  by  the  meeting  of  two 
lines  on  the  surface  of  a  sphere  or  globe. 
Trace  any  two  meridians  on  the  terres- 
trial globe,  as  those  of  London  and  Peters- 
burg, from  the  equator  northwards ; 
they  will  meet  at  the  north  pole,  and 
there  form  a  spherical  angle,  which, 
measured  on  the  equator,  will  be  found 
equal  to  30°. 

3.  Angle,  Solid.  The  angle  formed  by 
three  or  more  planes  which  meet  at  the 
same  point,  as  the  angles  of  solid 
bodies. 

4.  Angle,  Re-entrant.  An  angle  whose 
vertex  is  turned  inwards,  and  which  is 
consequently  greater  than  two  right 
angles.     It  is,  in  fact,  a  convex  angle. 

5.  Angle  of  Contingence,  or  Contact. 
The  angle  made  by  a  curved  line  and  its 
tangent  to  it.  at  the  point  of  contact. 

6.  Angle,  Rectilinear,  Curvilinear,  Mix- 
tilinear.  1.  The  first  is  formed  by  the 
inclination  of  two  right  lines  to  each 
other,  which  meet  together,  but  are  not 
in  the  same  right  line.  2.  The  second  is 
formed  by  the  tangents  of  two  curves, 

26 


where  they  meet  each  other.  3.  The 
third  is  formed  by  the  meeting  of  a  right 
line  and  a  curved  line. 

7.  Angles,  Adjacent  and  Contiguous. 
1.  When  a  side  of  one  angle,  being  pro- 
duced, forms  a  side  of  another,  the  two 
angles  are  said  to  be  adjacent.  Hence, 
adjacent  angles  are  supplements  to  each 
other,  making  together  180°,  or  two  right 
angles.  2.  When  two  angles  have  the 
same  vertex,  and  one  side  common  to 
both,  they  are  said  to  be  contiguous. 

8.  Angles,  Opposite  and  Alternate. 
1.  When  two  angles  have  their  sides  mu- 
tually continuations  of  each  other,  they 
are  said  to  be  vertical  or  opposite,  and  it 
may  be  shown  that  opposite  angles  are 
equal,  because  they  have  a  common  sup- 
plement. 2.  The  angles  which  are  made 
on  the  opposite  sides  of  a  line  cutting 
two  parallel  lines,  are  called  alternate. 

9.  Angles,  Supplemental  and  Comple- 
mental.  1.  When  two  angles  are  toge- 
ther equal  to  two  right  angles,  they  are 
said  to  be  supplemental,  and  one  is  called 
the  supplement  of  the  other.  2.  When  two 
angles  are  together  equal  to  a  right  angle, 
they  are  said  to  be  complemental,  and  one 
is  said  to  be  the  complement  of  the  other. 

II.  In  Optics. 

10.  Angle  of  Vision.  The  angle  con- 
tained between  lines  coming  from  op- 
posite parts  of  an  object  and  meeting  in 
the  eye.  On  the  magnitude  of  this  angle 
depends  the  apparent  magnitude  of  all 
objects  perceptible  to  the  sight. 

11.  Angle  of  Incidence.  The  angle 
contained  between  the  line  described 
by  the  incident  ray,  and  a  line  per- 
pendicular to  the  surface  on  which  the 
ray  strikes,  raised  from  the  point  of  in- 
cidence. • 

12.  Angle  of  Reflection.  The  angle 
contained  between  the  line  described  by 
the  reflected  ray,  and  a  line  perpen- 
dicular to  the  reflecting  surface,  at  the 
point  from  which  the  ray  is  reflected. 

13.  Angle  of  Refraction.  The  angle 
contained  between  the  line  described  by 
the  refracted  ray,  and  a  line  perpendicu- 
lar to  the  refracting  surface  at  the  point 
in  which  the  ray  passes  through  that 
surface. 

III.  In  Astronomy. 

14.  Angle  at  the  Sun.  The  angle  under 
which  the  distance  of  a  planet  from  the 
ecliptic  appears  at  the  sun. 

15.  Angle  of  Longitude.  The  angle 
formed  by  the  circle  of  a  star's  longitude 


ANG 


ANI 


with  the  meridian  at  the  pole  of  the 
ecliptic. 

16.  Angle,  Horary.  The  angle  formed 
with  the  meridian  of  any  place  by  a  great 
circle,  which  passes  through  a  star  and 
the  pole. 

17.  Angle  of  Commutation.  The  angle 
at  the  sun,  formed  by  two  lines,  one 
drawn  from  the  earth,  and  the  other 
from  the  place  of  the  planet  reduced  to 
the  ecliptic,  meeting  in  the  sun's  centre. 

18.  Angle  of  Elongation.  The  angle 
formed  by  two  lines  drawn  from  the 
earth,  the  one  to  the  sun,  and  the  other 
to  the  planet ;  or  it  is  the  difference  be- 
tween the  sun's  place  and  the  geocentric 
place  of  the  plaaet. 

19.  Angle  of  Erection.  An  inequality 
in  the  motion  of  the  moon,  by  which, 
at  or  near  her  quadratures,  she  is  not 
in  the  line  drawn  through  the  centres 
of  the  earth  and  sun,  as  she  is  at  the 
syzygies,  but  makes  an  angle  with  that 
line  of  about  2°  51'. 

IV.  In  Mechanics. 

20.  Angle  of  Draught.  A  term  applied 
to  express  that  direction  of  a  drawing 
power  which  is  best  adapted  to  overcome 
friction  and  weight ;  and  this  is  found  to 
be  the  angle  made  by  the  line  of  direc- 
tion with  a  line  upon  the  plane  4\er 
which  the  body  is  drawn,  and  perpendi- 
cular to  that  line  of  direction 

21.  Angle  of  Direction  and  of  Elevation. 

1.  In  mechanics,  the  angle  of  direction 
is  that  comprehended  between  the  lines 
of   direction  of  two   conspiring    forces. 

2.  The  angle  of  elevation  is  that  which  is 
comprehended  between  the  line  of  direc- 
tion and  any  plane  upon  which  the  pro- 
jection is  made,  whether  horizontal  or 
oblique. 

22.  Angle  of  Incidence  and  of  Reflection. 
When  an  elastic  body  strikes  an  elastic 
plane  at  a  certain  angle,  this  body  re- 
turns under  the  same  angle,  but  in  the 
opposite  direction ;  the  former  is  called 
the  angle  of  incidence,  the  latter  the 
angle  of  reflection. 

V.  In  Zoology. 

23.  Angle,  Facial.  An  angle  com- 
posed of  two  lines,  one  drawn  in  the 
direction  of  the  basis  of  the  skull,  from 
the  ear  to  the  roots  of  the  upper  incisor 
teeth,  and  ,the  other  from  the  latter  point 
to  the  most  projecting  part  of  the  fore- 
head. 

24.  Angle,  Frontal.  In  Ornithology,  the 
angle  which  the  culmen,  or  upper  part  of 
the  beak,  makes  with  the  forehead. 

27 


VI.  In  Fortification. 

25.  Angles  in  Fortification.  These  are 
of  two  sorts,  real  and  imaginary.  1.  Real 
angles  are  those  which  actually  exist  and 
appear  in  the  wor^s,  as  the  flanked  angle, 
the  angle  of  the  epaule,  the  angle  of  the 
flank,  and  the  re-entering  angle  of  the 
counterscarp.  2.  Imaginary  or  occult 
angles  are  those  which  are  only  subser- 
vient to  the  construction,  and  which  ex- 
ist no  longer  after  the  fortification  is 
drawn,  as  the  angle  of  the  centre,  the 
angle  of  the  polygon,  the  flanking  angle, 
the  salient  angle  of  the  counterscarp,  &c. 

ANGUI'NID^E  {unguis,  a  snake). 
Slow-worms ;  a  family  of  Ophidian  rep- 
tiles, which  combine  the  characters  of 
the  serpents  and  the  lizards.  They  ap- 
proach the  latter  in  the  possession  of 
rudimentary  legs  under  the  skin,  as  well 
as  in  other  points  of  their  organization. 
The  slow-worm  of  this  country,  erro- 
neously called  blind  worm,  has  remark- 
ably brilliant  eyes. 

A'NGULAR  MOTION.  The  varia- 
tion in  the  angle  described  by  a  line,  or 
radius,  which  connects  a  moving  body 
with  the  centre  about  which  it  moves. 
Thus,  a  pendulum  has  an  angular  motion 
about  its  point  of  suspension,  and  the 
planets  have  an  angular  motion  about  the 
sun. 

Angular  Intervals,  in  Astronomy,  mea- 
sured by  means  of  the  transit  instrument 
and  clock,  are  those  arcs  of  the  equinoc- 
tial, which  are  intercepted  between  cir- 
cles of  declination  passing  through  the 
objects  observed. 

A'NHYDRITE  (a,  priv.,  vdap,  water). 
Sulphate  of  lime ;  a  mineral  occurring  in 
a  crystalline  form  without  water. 

A'NHYDROUS  (a,  priv.,  vdap,  water). 
Without  water ;  a  term  applied  to  crys- 
tals and  gases  which  are  deprived  of 
water.     See  Hydrate. 

A'NILIC  ACID.  An  acid  formed  by 
the  action  of  nitric  acid  upon  indigo,  and 
named  from  the  anil,  a  plant  growing  in 
America,  from  the  leaves  of  which  indigo 
is  prepared.  The  acid  was  formerly 
called  indigotic. 

A'NILINE.  An  oily  liquid,  which 
distils  over  when  finely-pulverized  indigo 
is  decomposed  by  a  highly  concentrated 
solution  of  caustic  potash  or  soda,  in  a 
retort. 

A'NIMA.  The  name  given  by  Stahl 
to  the  intelligent  agent  supposed  to  pre- 
side over  many  paits  of  the  animal  eco- 
nomy. This  is  the  archceus  of  Van  Hel- 
mont,  and  has  been  termed  the  vital 
C2 


ANI 

principle,  the  spirit  of  animation,  &c.  In 
pure  Latin,  the  word  denotes  hreath, 
animal  life,  the  air  we  breathe;  and  is 
sometimes  synonymous  with  animus,  the 
soul. 

ANIMAL  KINGDOM.  The  appella- 
tion given  to  that  great  division  of  natu- 
ral   bodies,    to    which    animals    belong. 

I.  Sub-kingdom  Vertebrata. 

Myelencephala  (Owen) 
Spinicerebrata  (Grant), 


ANN 

These  were  distributed  by  Cuvier  into 
four  large  groups,  viz.  Vertebrata,  Mol- 
lusca,  Articulata,  and  Radiata.  This 
arrangement  has,  however,  been  modi- 
fied, and  new  terms  introduced  by  more 
recent  writers,  as  will  appear  in  the  sub- 
joined table : 


Class  1.  Mammalia. 

2.  Aves. 

3.  Amphibia. 
II.  Sub-kingdom  Articulata. 

Homogangliata  (Owen). 
Diploneura  (Grant). 
Annulosa  (Macleay). 
Class  1.  Cirrhopoda.  i  4.  Insecta. 

2.  Annellida.      5.  Arachnida. 

3.  Myriapoda.  |  6.  Crustacea. 


4.  Reptilia. 

5.  Pisces. 

II.  Sub-kingdom  Mollusca. 

Heterogangliata  (Owen). 

Cycloglangiata  (Grant). 

Class   1.  Cephalopoda,  i  4.  Pteropoda. 

2.  Gasteropoda.      5.  Conchifera. 

3.  Brachiopoda.   |  6.  Tunicata. 


IV.  Sub-kingdom  Radiata. 
Cycloneura  (Grant). 


Nematoneura  (Owen). 


Class  Radiaria,  Lamarck. 


Acrita  (Macleay). 


Echinoderma,  Cuvier. 


Class  Polypi,  Cuvier. 


Acalepha,  Cuvier. 


Ciliobrachiata,  Farre. 


Anthozoa,  Ehrenb. 
Class  Entozoa,  Rudolphi. 


Nudibrachiata,  Farre. 


Coelelmintha,  Owen. 


Class  Infusoria,  Cuvier. 


Sterelmintha,  Owen. 


Rotifera,  Ehrenb. 

ANIMAL  MAGNETISM.  A  supposed 
agent,  of  a  peculiar  nature,  discovered 
by  Anton  Mesmer,  and  said  to  be  capable 
of  producing,  in  some  mysterious  way, 
the  most  powerful  effects  on  the  human 
economy. 

ANIMALCULES  (dim.  of  animal). 
Microscopic  animals  existing  in  rivers  and 
ponds,  and  in  all  animal  and  vegetable  in- 
fusions. The  term  was  originally  applied 
to  a  vast  number  of  creatures  widely  dif- 
fering from  one  another  in  every  parti- 
cular except  minuteness  of  size,  but  is 
now  restricted  to  that  division  of  infu- 
sorial animalcules,  termed,  from  their 
digestive  apparatus,  polygastrica. 

A'NION  (dviov,  that  which  goes  up). 
A  term  applied  by  Mr.  Faraday  to  the 
body  which  passes  to  the  positive  pole, 
or  anode  of  the  decomposing  body,  as 
it  is  separated  by  electricity.    See  Ration. 

ANISO'BRYOUS  ('dviaos,  unequal, 
28 


Polygastria,  Ehrenb. 
fipvw,  to  grow).  That  which  grows  un- 
equally; a  term  applied  by  some  writers 
to  monocotyledonous  plants,  which,  hav- 
ing only  one  cotyledon,  grow  with  unequal 
force  on  the  two  sides  of  their  axis.  For 
the  same  reason,  such  plants  have  been 
called  anisodynamous,  from  dova/jiis,  force. 

ANISOSTE'MONOUS  (fotaos,  un- 
equal, o-rr/juwv,  a  stamen).  A  term  ap- 
plied to  plants  in  which  the  number  of 
stamens  does  not  correspond  with  the 
number,  or  any  power  of  the  number,  of 
the  petals  or  of  the  sepals. 

ANNEALING.  The  process  of  heat- 
ing a  metallic  body,  and  suffering  it  to  cool 
again  in  a  moderate  temperature,  in 
order  to  restore  its  malleability,  which  it 
is  apt  to  lose  tinder  the  operation  of  ham- 
mering. If  cooled  too  suddenly,  it  be- 
comes extremely  brittle.  The  Annealing 
of  Glass  is  conducted  in  the  same  man- 
ner, and  is  necessary  to  prevent  its  flying 


ANN 


ANO 


to  pieces  on  the  application  of  violence 
or  a  high  temperature. 

ANNE'LLIDA  (annellus,  a  little  ring). 
A  class  of  animals  which  have  their 
bodies  formed  of  a  great  number  of  small 
rings,  as  the  earth-worm.  They  were 
distinguished,  in  Cuvier's  arrangement, 
by  their  red  blood,  and  by  the  circulation 
of  their  blood  in  a  double  system  of  com- 
plicated vessels.  MM.  Audoin  and  Milne 
Edwards  adopt  four  divisions,  differing 
in  habits  and  structure : — 

1.  Errantia.  Walking  or  swimming 
animals,  rarely  sedentary.  Head  distinct 
from  the  body ;  with  antennae,  eyes,  and 
generally  jaws.  These  are  the  dorsi- 
branchia  of  Cuvier,  the  nereidce  of  Sa- 
vigny. 

2.  Tubicola.  Sedentary  animals,  in- 
habiting the  interior  of  solid  tubes.  Head 
not  distinct ;  without  eyes,  antennae,  or 
jaws. 

3.  Terricola.  Animals  furnished  with 
bristles  instead  of  feet ;  dwelling  in  the 
earth.  No  distinct  head,  antennae,  or 
jaws. 

4.  Suctoria.  Animals  without  feet  or 
bristles,  but  furnished  at  each  extremity 
of  the  body  with  a  prehensile  cavity  or 
sucker.  No  distinct  head;  but  generally 
with  eyes  and  jaws.     Chiefly  parasitic. 

Divisions  of  Dr.  Grant.  Dr.  Grant 
divides  the  Annellida  into  the  following 
orders,  by  the  differences  of  their  respi- 
ratory organs : — 

1.  Apneumata,  or  those  which  have 
no  perceptible  respiratory  organs,  as 
the  nais. 

2.  Cephalobranchia,  or  those  which 
present  distinct  branchiae  at  the  ce- 
phalic extremity  of  the  body,  as  the 
serpula. 

3.  Dorsibranchia,  or  those  which 
have  external  or  internal  branchiae 
disposed  along  the  back  of  the  trunk, 
as  the  nereis. 

4.  Pulmonata,  or  those  which  breathe 
by  pulmonary  sacs,  as  the  lumbricus. 

ANNUAL  REVOLUTION.  The 
yearly  course  of  the  earth  in  its  orbit 
round  the  sun.  It  must  be  distinguished 
from  the  diurnal  motion.  The  latter 
produces  only  day  and  night ;  the  former 
causes  the  different  lengths  of  day  and 
night,  as  well  as  the  phenomena  of  the 
seasons. 

ANNULAR  ECLIPSE  (annulus,  a 
ring).  A  term  applied  in  Astronomy  to 
those  eclipses  of  the  sun,  in  which  a  ring 
of  light  is  visible  around  the  dark  body 
of  the  moon. 


A'NNULATE  {annulus,  a  ring). 
Ringed ;  surrounded  or  marked  by  rings, 
as  certain  vessels  in  plants ;  also  certain 
animals  which  appear  to  be  composed  of 
a  succession  of  rings. 

ANNULO'SA  (annulus,  a  ring).  A  de- 
signation given  by  Macleay  to  the  divi- 
sion of  animals  included  in  the  Articu- 
lata  of  Cuvier,  the  Homogangliata  of 
Owen,  and  the  Diploneura  of  Grant. 
Macleay's  term  relates  merely  to  their 
annulated  skin. 

A'NNULUS.  A  ring.  1.  The  geome- 
trical term  for  a  solid  formed  by  the  revo- 
lution of  a  circle  about  a  straight  line 
exterior  to  its  circumference,  as  an  axis, 
and  in  the  plane  of  the  said  circle.  2.  The 
term  annulus  is  applied,  in  Botany,  to 
that  part  of  the  theca  of  ferns,  where  the 
stalk  is  united  with  its  side ;  and  to  the 
collar  which  surrounds  the  stipes  in  the 
highest  forms  of  the  fungi. 

A'NODE  (ava,  upwards,  666s,  a  way). 
A  term  applied  by  Mr.  Faraday  to  that 
part  of  the  surface  of  a  decomposing 
body  which  the  electric  current  enters — 
the  part  immediately  touching  the  posi- 
tive pole.    See  Kathode. 

ANODO'NTINjE  (a,  priv.,  bdovs, 
636i/Tor,  a  tooth).  A  sub-family  of  the 
Unionidce,  or  River  Mussels,  named  from 
the  genus  Anodon,  the  shell  of  which 
has  no  articular  processes,  or  teeth,  at  the 
hinge. 

ANODY'NE  (ai/wdi/i/o?,  without  pain). 
That  which  relieves  from  pain.  An  agent 
of  this  kind  which  induces  sleep,  is  called 
a  hypnotic ;  if  it  causes  insensibility,  it 
is  termed  a  narcotic. 

ANO'MALI'STIC  YEAR  (dvdfiaXo?, 
irregular).  The  interval  which  occurs 
between  two  consecutive  returns  of  the 
earth  to  the  perihelion,  or  its  least  dis- 
tance from  the  sun.  The  difference  be- 
tween the  anomalistic  and  the  tropical  or 
common  year  is  owing  to  the  orbit  of  the 
earth  representing  an  ellipse,  of  which 
the  major  axis  has  a  slow  motion  of 
11  ".8  per  annum  in  advance.  In  de- 
scribing this  arc,  the  earth  occupies 
4'  39".  7,  which,  being  added  to  the  side- 
real period,  gives  365d.  6h.  13m.  49s.3 
for  the  anomalistic  year.  See  Tropical 
Year. 

ANO'MALY  (dvcofxaXo?,  irregular). 
A  term  applied,  in  Astronomy,  to  the 
angle  through  which  the  radius  drawn 
from  a  planet  to  the  sun  has  moved  with 
the  planet  from  the  time  when  this  was 
at  its  least  distance  from  the  sun.  The 
mean  anomaly  is  proportioned  to  the  time 
C3 


A  N  T 


ANT 


of  description :  to  derive  the  true  ano- 
maly from  this,  is  to  find  the  mean  angu- 
lar motion  which  would  have  been  per- 
formed had  the  motion  in  angle  been 
uniform  instead  of  the  motion  in  area, 
and  involves  a  problem  of  the  transcen- 
dental kind. 

ANOMOU'RA  (ai/o/uof,  unlawful, 
ovpd,  a  tail).  A  family  of  Decapods, 
distinguished  by  the  very  unusual  con- 
formation of  the  tail :— instead  of  being 
encased  in  a  hard  coat  of  mail,  as  in  the 
macroura,  the  hinder  part  of  the  body  is 
soft  and  coriaceous,  possessing  only  a 
few  detached  calcareous  pieces,  ana- 
logous, it  is  true,  to  those  found  in  the 
lobster,  but  strangely  altered  in  struc- 
ture. They  are  known  by  the  name  of 
soldier-crabs  or  hermit-crabs. 

ANONA'CE.E.  An  order  of  Dicotyle- 
donous plants,  named  from  the  typical 
genus  Anona,  and  characterized  by  a 
powerful  aromatic  taste  and  smell  in  all 
their  parts.  Trees  or  shrubs,  with  leaves 
alternate ;  petals  6,  hypogynous ;  ovaries 
numerous ;  fruit  consisting  of  many  car- 
pels, distinct  or  concrete  into  a  fleshy 
mass. 

A'NOPLOTHE'RIUM  (SvoTrXoc,  un- 
armed, dnpiov,  a  wild  beast).  An  extinct 
fossil  quadruped,  belonging  to  the  order 
Pachydermata,  resembling  a  pig.  The 
name  is  derived  from  the  animal  having 
been  remarkably  deficient  in  the  means 
of  defence,  from  the  form  of  its  teeth, 
and  the  absence  of  claws,  hoofs,  and 
horns. 

ANO'RMAL  (anormis,  without  rule). 
Irregular;  contrary  to  the  usual  rule; 
or,  more  precisely,  destitute  of  rule.  See 
Abnormal. 

ANO'RTHITE  (dv-,  the  negative  pre- 
fix, of  which  a,  priv.,  is  a  shortened  form ; 
bp66?,  upright).  A  mineral  consisting  of 
silica,  alumina,  lime,  magnesia,  and 
oxide  of  iron.  Its  name,  which  signifies 
without  right  angles,  distinguishes  it 
from  felspar,  two  of  whose  cleavages  are 
at  right  angles  to  each  other. 

ANOU'RA  (a  priv.,  ovpa,  a  tail).  An 
order  of  Amphibious  animals,  comprising 
the  Frogs  and  Toads,  in  which  the  gills 
and  the  tail  disappear  on  their  reaching 
the  perfect  state. 

A'NSjE  (ansa,  a  handle).  In  Astro- 
nomy, those  parts  of  Saturn's  ring  which 
project  beyond  the  disk  of  the  planet,  and 
appear  like  handles  to  the  body  of  the 
planet 

ANTAGONIST  POWERS  (uvtI,  op- 
posite, aywi/t'tojucw,  to  struggle).  Two 
30 


powers  in  nature,  of  which  the  action  of 
one  antagonizes,  or  counteracts,  that  of 
the  other;  hence  a  kind  of  balance  or 
equilibrium  is  maintained,  and  the  de- 
structive effects,  which  would  ensue  from 
the  unchecked  operation  of  either,  pre- 
vented. Of  this  kind  are  the  centrifugal 
and  centripetal  forces  in  Astronomy,  the 
attractive  and  repulsive  agencies  in  Che- 
mistry, &c. 

ANTA'RCTIC  {dvrl,  apart™?,  from 
apKTot,  the  bear).  That  which  is  oppo- 
site to  the  Arctic. 

1.  The  Antarctic  Pole  is  the  South 
Pole,  and  is  opposite  to  the  Arctic  or 
North  Pole,  which  points  to  the  constel- 
lations of  the  Great  and  the  Little  Bears. 

2.  The  Antarctic  Circle  is  an  imaginary 
circle  distant  23°  27'. 5  from  the  Antarctic 
or  South  Pole,  and  66°.  5  from  the  equator, 
and  parallel  to  it. 

3.  The  Antarctic  Ocean  is,  properly 
speaking,  the  ocean  between  the  Ant- 
arctic circle  and  the  South  Pole. 

ANTA'RES.  The  Scorpion's  heart;  a 
star  of  the  first  magnitude,  marked  a,  in 
the  constellation  Scorpio. 

ANTECEDENT  (antecedo,  to  go  be- 
fore). In  Logic,  that  part  of  a  conditional 
proposition  from  which  the  other  part,  or 
the  consequent,  results  ;  the  connexion 
between  the  two,  expressed  by  the  word 
"  if,"  is  called  the  consequence.  In  the 
proposition,  "If  logic  is  useless,  it  de- 
serves to  be  neglected,"  both  antecedent, 
and  consequent  are  false ;  yet  the  whole 
proposition  is  true — the  consequent  fol- 
lows from  the  antecedent. 

The  term  Antecedent,  in  Mathematics, 
denotes  the  former  of  the  two  terms  of  a 
ratio,  as  distinguished  from  the  latter 
term,  or  consequent.  Thus,  in  the  con- 
tinued proportion, 

2 :  4  : :  3 ;  6 ; :  4 : 8 : :  5 ;  io,  &c 

2,  3,  4,  5,  &c,  are  antecedents,  and  4,  6, 
8,  10,  &c,  are  consequents.  Antecedents 
and  consequents  may  be  inverted,  with- 
out destroying  the  proportion.    Thus,  if 

2 :  4  : :  5 :  io, 

it  is  equally  true  that 

4  : 2 ; :  io :  5. 

ANTECEDE'NTIA.  An  astronomical 
term,  denoting  that  a  celestial  body  moves 
contrary  to  the  order  of  the  signs  of  the 
Zodiac  ;  it  is  then  said  to  move  in  ante- 
cedentid.  When  it  moves  in  the  order  of 
the  signs,  it  is  said  to  move  in  conse- 
quentid. 

ANTELO'PIDjE.  The  Antelope  tribe ; 
a  family  of  the  Ruminantia,  remarkable 


ANT 


ANT 


for  the  activity  of  their  movements,  and 
for  the  solidity  of  the  core,  or  bony 
support  of  their  horns.  The  name  ante- 
lope is  a  corruption  of  antholops,  and  this 
is  derived  from  ikvOos,  a  flower,  and 
wf,  the  eye, — in  allusion  to  the  beautiful 
eyes  of  the  gazelle,  or  "antholops"  of 
Eustathius. 

ANTE'NNjE  {antenna,  a  yard-arm). 
The  articulated  horns,  or  jointed  feelers, 
with  which  the  heads  of  insects  and 
crustaceans  are  invariably  furnished.  In 
the  latter  class  they  are  usually  four  in 
number,  consisting  each  of  a  scape,  a 
pedicel  of  two  joints,  and  a  clavolet,  which 
is  divided  into  many  minute  joints.  The 
term  antennae  is  sometimes  applied  to 
the  analogous  parts,  which  are  not 
jointed,  in  worms  and  other  animals. 

ANTE'RIOR.  Before.  This  term, 
applied  to  bivalve  shells,  denotes  that 
valve  in  which  the  ligament  is  not  placed. 

ANTHE'LION  {dvii,  opposite,  rjXtor, 
the  sun).  A  bright  spot,  opposite  to  the 
sun.  The  horizontal  circle  attendant 
upon  halos  is  usually  accompanied  by 
parhelia,  and  occasionally  by  anthelia. 

A'NTHER  (dv6np6s,  from  bvMm,  to 
flourish).  The  part  of  a  plant  which  has 
hitherto  been  considered  as  the  fertilizing 
organ.  It  is  the  essential  part  of  the 
stamen,  consisting,  in  most  cases,  of  two 
thecae  placed  at  the  top  of  the  filament, 
and  hence  called  the  bilocular  anther. 
The  anther  is  termed, 

1.  Innate,  when  it  is  attached  to  the 
filament  by  its  base,  as  in  sparganium. 

2.  Adnate,  when  it  is  attached  to  the 
filament  by  its  back,  as  in  polygonum. 

3.  Versatile,  when  it  is  attached  to  the 
filament  by  a  single  point  of  the  con- 
nective, from  which  it  lightly  swings,  as 
in  grasses. 

4.  Antica  or  introrsa,  when  the  line  of 
its  dehiscence  is  towards  the  pistil. 

5.  Postica  or  extrorsa,  when  the  line  of 
its  dehiscence  is  towards  the  petals. 

ANTHERI'DIA.  Little  anthers;  a 
designation  of  the  jointed  filaments 
which  occur  in  mosses,  containing  vibrios 
lodged  in  mucous  cells,  and  surround 
the  rudiment  of  the  future  theca.  They 
are  also  called  staminidia,  or  little  sta- 
mens, though  they  appear  to  have  no 
analogy  to  the  stamens  of  flowering 
plants.     ' 

A'NTHIARIN.  A  gum  resin,  obtained 
from  the  Anthiaris  toxicaria,  the  most 
deadly  of  the  Upas  poi>ons,  employed  by 
the  inhabitants  of  the  East  Indian  Archi- 
pelago to  poison  their  arrows. 
31 


ANTHOCA'RPOUS  {uvdo?,  a  flower, 
/captor,  fruit).  A  term  applied,  in  Bo- 
tany, to  multiple  fruits  formed  by  masses 
of  inflorescence  in  a  state  of  adhesion,  as 
the  pine-apple,  the  fir-cone,  &c. 

ANTHO'DIUM  (i„0«3»ie,  flowery,  full 
of  flowers).  A  term  sometimes  applied 
by  botanists  to  the  inflorescence  of  the 
Compositae,  which  is  more  commonly 
called  a  capitulum.  In  either  case  it  is 
merely  a  depressed  spike. 

ANTHO'PHORUM  Cdv0os,  a  flower, 
$e'pa),  to  bear).  A  term  applied  by  De 
Candolle  to  an  elongated  internode  which 
occurs  below  the  receptacle  in  the  Caryo- 
phyllaceae,  and  bears  on  its  summit  the 
petals  and  stamens. 

ANTHOPHY'LLITE  (fefer,  a  flower, 
<pi>\\ov,  a  leaf).  A  massive  mineral,  of  a 
brownish  colour,  found  at  Konigsberg  in 
Norway.  Its  appearance  suggests  that 
of  the  anthophyllus,  or  clove,  which  de- 
rives its  name  from  the  fragrance  of  its 
flowers  and  the  beauty  of  its  leaves. 

ANTHOZO'A  (&i/0o?,  a  flower,  £u>ov, 
an  animal).  A  term  applied  by  Ehren- 
berg  to  a  class  of  polyps,  including  the 
actinia  and  allied  species,  commonly 
called  animal-flowers. 

ANTHRACITE  (fivflpaf,  a  burning 
coal).  A  species  of  slaty  coal  found  in 
the  transition-rock  formation,  and  often 
called  stone  coal,  glance  coal,  and  blind 
coal.  It  differs  from  common  coal,  which 
it  frequently  accompanies,  in  containing 
no  bituminous  substances,  and  in  not 
yielding  inflammab'e  gases  by  distillation. 
It  consists,  in  some  specimens,  of  95  per 
cent,  of  carbon.  Its  varieties  are  the 
massive  or  conchoidal,  the  slaty,  and  the 
columnar. 

A'NTHRACOTHEBITJM  {&v9{>a$,  a 
coal,  9npiov,  a  wild  beast).  The  name  of 
an  extinct  quadruped,  supposed  to  belong 
to  the  Pachydermata,  the  bones  of  which 
were  first  found  in  lignite  and  coal  of  the 
tertiary  strata. 

ANTHRANI'LIC  ACID.  An  acid 
obtained  by  the  action  of  fused  potash 
on  indigo. 

ANTHROPO'GRAPHY  (3i/0pa»ropt 
man,  ypd^oo,  to  describe).  A  description 
of  mankind,  with  reference  to  their  geo- 
graphical distribution,  the  physical  cha- 
racter and  language  of  their  classes,  their 
distinction  into  nations  and  tribes,  and 
their  religious  and  domestic  habits.  See 
Ethnography. 

ANTHROPO'LOGY  ('dvOpunot,  man, 
\6io?,  an  account).  The  science  or  theory 
of  man,  with  reference  to  the  physiolo- 
C4 


ANT 


APE 


gical  and  the  mental  phenomena  of  his 
nature.  The  term  is  sometimes  restricted 
to  the  science  of  Anatomy. 

ANTILO'GARITHM.  A  term  de- 
noting the  number  to  the  logarithm :  thus, 
100  is  the  antilogarithm  of  2.  because  2 
is  the  logarithm  of  100.  Among  the 
French,  the  term  is  more  generally  em- 
ployed in  the  sense  of  the  complement  of 
the  logarithm,  viz.  the  remainder  pro- 
duced by  subtracting  the  logarithm  from 
the  next  higher  term  in  the  series  1,  10, 
100,  &c. 

A'NTIMONY.  A  brittle  whitish 
metal,  usually  found  associated  with 
sulphur.  Sometimes  this  sulphuret  is 
termed  crude  antimony,  to  distinguish  it 
from  the  pure  metal,  formerly  called 
regulus  of  antimony.  Its  name  has  been 
fancifully  derived  from  its  fatal  effects 
upon  some  monks  {anti-moine),  upon 
whom  Valentine  is  said  to  have  tested  its 
properties. 

Argentine  flowers  of  Antimony  is  a 
name  for  the  sesqui-oxide  of  the  metal, 
derived  from  its  silvery  whiteness.  In 
the  powder  of  Algaroth,  the  physician 
Algarotti  has  given  his  name  to  the  oxy- 
chloride.  The  glass,  liver,  and  crocus  of 
antimony  are  oxy-sulphurets  of  the  old 
apothecaries ;  the  saffron  is  a  substance 
formed  by  dissolving  the  oxide  of  the 
metal  out  of  the  glass,  by  means  of  acids. 
The  kermes  mineral  is  a  sulphuret,  re- 
sembling in  colour  the  insect  kermes ; 
the  golden  sulphuret  is  a  similar  sub- 
stance. The  butter  of  antimony  is  the 
sesqui-chloride,  a  soft  solid,  of  the  con- 
sistence of  butter. 

A'NTIPERISTA'LTIC  {Avrl,  opposite, 
ireoiaraXTLKo^ ,  clasping  and  compressing). 
A  term  denoting  that  the  vermicular  con- 
tractions of  a  muscular  tube  follow  one 
another  in  a  direction  the  reverse  of  the 
ordinary  one. 

ANTI'PODES  (avTi,  opposite,  Troder, 
feet).  The  inhabitants  of  our  globe  who 
live  diametrically  opposite  to  each  other, 
and  who  may  therefore  be  said  literally 
to  stand  feet  to  feet.  All  gravitate  to  the 
centre  of  the  earth;  and  the  terms  up  and 
down  must  be  considered,  in  astronomi- 
cal language,  merely  in  relation  to  bodies 
being  further  from  or  nearer  to  the 
centre.  The  antipodes  differ  in  longi- 
tude 180°,  and  the  one  class  of  inhabi- 
tants has  the  same  latitude  north  as 
the  other  has  south. 

ANTI'SCII     (Jvt'i,      opposite,      anta, 
a  shadow).      Those  inhabitants   of   the 
earth,  whose  shadows  fall  in  opposite  di- 
32 


rections.  The  inhabitants  of  the  north 
and  south  temperate  zones  are  always 
antiscians ;  those  residing  within  the 
tropics,  are  antiscians  during  only  one 
season  of  the  year.     See  Ascii. 

ANTISE'PTIC  {!xvtI,  against,  o^ttw, 
to  putrefy).  A  term  applied  to  substances 
which  prevent  putreafction  in  animal  or 
vegetable  matter,  as  common  salt. 

ANTITHESIS  (dVTi0e<rts,  opposition). 
In  Rhetoric,  this  term  denotes  contrast  of 
ideas,  whether  expressed  by  single  words 
or  by  single  clauses.  Quinctilian  renders 
it  by  the  Latin  term  contrapositum,  and 
the  following  is  an  illustration  from 
Cicero :— u  quod  scis,  nihil  prodest ;  quod 
nescis,  multum  obest." 

ANTI'TROPOUS  (ivti,  against,  Tpe™, 
to  turn).  Straight,  and  having  a  direction 
contrary  to  that  of  the  body  to  which  it 
belongs ;  a  term  applied  in  Botany  to  the 
direction  of  the  embryo  compared  with 
that  of  the  seed :  thus,  if  the  nucleus  be 
erect,  the  embryo  may  be  inverted,  and 
it  is  then  said  to  be  antitropous,  as  in  the 
nettle.  The  radicle  of  the  embryo  is  then 
turned  to  the  point  most  remote  from  the 
hilum. 

A'NTLIA.  The  Latin  term  for  a 
pump,  and  hence  applied  to  the  spiral 
instrument  of  the  mouth  of  butterflies 
and  allied  insects,  by  which  they  pump 
up  the  juices  of  plants. 

A'NTLIA  PNEUMATIC  A.  The  Air- 
pump  ;  the  name  of  a  constellation  in 
the  southern  hemisphere. 

ANTCE'CI  (uvTt,  opposite,  oIkos,  a  ha- 
bitation). Those  who  live  under  the  same 
meridian,  and  at  the  same  distance  from 
the  equator,  but  the  one  party  having 
north,  and  the  other  south  latitude.  See 
Ascii. 

A'NTONOMA'SIA  (dvri,  instead  of, 
ovofxa,  a  name).  A  rhetorical  figure,  by 
which  a  proper  name  is  used  for  a  cha- 
racteristic appellation,  as  when  a  bene- 
factor is  called  "  a  Howard,"  a  despot  "  a 
Turk;''  or  vice  versa,  as  when  a  queen 
is  called  "Her  Majesty,"  or  Homer  "the 
prince  of  poets." 

A'ORIST  (uopto-Tov,  indeterminate). 
A  term  applied,  in  Grammar,  to  those 
inflexions  of  the  verb  in  which  the  time 
of  the  action  is  undefined. 

A'PATITE  (uTrardu),  to  deceive).  Phos- 
phate of  lime  ;  a  mineral  which  occurs  in 
tin  veins,  and  possesses  phosphorescent 
properties.  It  is  named  from  its  having 
been  confounded  with  other  minerals. 

A'PERTURE  (apertura,  a  little  open- 
ing).   The  mouth  of  univalve  shells,  or 


APH 


A  P  0 


the  cavity  from  which  the  head  of  the 
animal  is  protruded. 

APE'TALOUS  (a,  priv.,  neraXov,  a 
petal).  A  term  applied  to  plants  which 
have  a  calyx,  but  no  corolla  or  petals. 
They  are  also  called  monochlamydeous, 
as  having  a  single  envelope,  viz.  a 
calyx. 

A'PEX.  The  pointed  top  of  a  cone. 
The  point  or  nucleus  of  a  shell;  and 
hence  the  term  is  applied  to  the  bosses 
of  bivalves,  the  points  or  tops  of  limpets, 
or  of  univalves.  In  Botany,  the  apex  of 
a  seed  is  the  extremity  opposite  to  the 
base;  the  apex  of  a  fruit  is  the  part 
where  the  remains  of  the  style  are 
found. 

APHjE'RESIS  (utto,  from,  alpeca,  to 
take).  Literally,  a  taking  away ;  a  gram- 
matical figure  by  which  words  are  shorn 
of  their  fair  proportions,  as  when  we  say 
'tis  for  "  it  is ;"  'tisn't  for  "  it  is  not." 

APHANI'PTERA  (a<pav^,  obscure, 
TTTepov,  a  wing).  The  Flea  tribe ;  an 
order  of  insects  which  have  only  the 
rudiments  of  wings,  in  the  form  of  little 
scales,  attached  to  the  second  and  third 
segments  of  the  body,  in  which  there  is 
no  proper  distinction  of  thorax  and  ab- 
domen.    They  undergo  metamorphosis. 

A'PHANITE  (a0ai/»/f,  indiscernible). 
A  greenstone  rock  containing  amphibole 
as  its  principal  ingredient,  and  named 
from  the  indiscernible  distinction  of  its 
parts.  It  is  the  lapis  corneus  trapezius 
of  the  old  mineralogists. 

APHE'LION  (iTro,  from,  riXtot,  the 
sun).  An  astronomical  term,  denoting 
the  greatest  distance  of  a  planet  from  the 
sun.  Its  opposite  point  is  the  perihelion, 
which  is  the  nearest  point  to  the  sun. 
These  two  points  are,  therefore,  the  two 
extremities  of  the  greater  axis  of  an 
orbit. 

A'PHID^E  (aphis,  the  plant-louse). 
The  Plant  Lice  ;  a  family  of  the  dimerous 
Homoptera,  which  infest  plants,  and  are 
vulgarly  supposed  to  give  rise  to  the  phe- 
nomena of  blights  and  honey-dew. 

APHLOGI'STIC  {d(p\6i«TTO?,  not  in- 
flammable). Without  flame;  a  term  ap- 
plied to  a  lamp  in  which  the  combustion 
is  effected  without  flame. 

A'PHRITE  (d(pP6t,  foam).  Earth  foam ; 
a  silvery-white,  friable  carbonate  of  lime, 
found  in  calcareous  veins. 

A'PHRIZITE.  A  variety  of  black 
tourmaline. 

APHY'LLOUS   (a,  priv.,    QvXXov,   a 
leaf).    Leafless  ;  a  term  applied  to  plants 
which    have   large  scales,  but  no  true 
33 


leaves ;  also  to  plants  in  which  the  true 
leaves  are  so  small  as  to  be  reduced  to 
scales. 

APIA'CEiE  (upturn,  parsley).  A  term 
recently  applied  to  the  family  of  Umbel- 
liferous plants,  as  more  consonant  with 
the  plan  of  forming  natural  orders.  See 
Umbelliferas. 

A'PICAL  (apex,  the  top  of  a  cone). 
Belonging  to  the  pointed  end  of  a  cone- 
shaped  body. 

APIO'CRINITE  (&mov,  a  pear,  Kpivov, 
a  lily).  Pear-encrinite ;  a  sub-genus  of 
fossil  encrinites,  in  which  the  stem  is 
rounded  and  dilated  at  its  upper  extre- 
mity into  a  pear-shaped  figure. 

APIS  MUSCA.  A  modern  southern 
constellation,  consisting  of  four  stars. 

APLANA'TIC  (a,  priv.,  nXdvn,  error). 
Free  from  error ;  a  term  applied  to  those 
optical  instruments  in  which  the  spheri- 
cal and  the  chromatic  aberrations  are 
completely  corrected.  This  term  is  more 
correct  than  achromatic,  which  merely 
implies  correction  of  the  chromatic  ab- 
erration ;  whereas  a  good,  or  aplanatic, 
instrument  has  its  errors  of  sphericity 
balanced  equally  with  those  of  colour. 

APLO'ME  (an\6os,  simple).  A  mine- 
ral usually  considered  as  a  variety  of  the 
garnet,  from  which,  however,  it  appears 
to  differ  in  its  primitive  form.  It  crys- 
tallizes in  rhombic  dodecahedrons,  de- 
rived by  the  simplest  laws  of  decrement 
from  the  cube. 

APOCA'RPOUS  (dno,  from,  Kapnos, 
fruit).  A  term  applied,  in  Botany,  to 
that  condition  of  the  carpels,  in  which 
they  are  distinct  from  one  another,  or 
easily  separable,  as  in  ranunculaceous 
plants.     See  Syncarpous. 

APOCY'NACEjE.  An  order  of  Dico- 
tyledonous plants,  named  from  the  typical 
genus  Apocynum,  and  agreeing  with 
Asclepiadaceae,  but  of  rather  more  sus- 
picious properties.  Trees  or  shrubs 
usually  milky,  with  leaves  opposite,  some- 
times whorled ;  corolla  monopetalous, 
hypogynous;  stamens  inserted  into  the 
corolla ;  ovaries  two ;  fruit  a  follicle, 
capsule,  drupe,  or  berry,  single  or  double. 

A'PODA  (a,  priv.,  ttoi/c,  7ro36s,  a  foot). 
An  order  of  Amphibious  animals,  com- 
prising only  one  genus,  the  Ccecilia,  of  a 
serpent-like  form,  and  altogether  desti- 
tute of  feet.  The  term  is  also  applied  to 
an  order  of  fishes  which  have  no  ventral 
fins.     See  Malacopterygii. 

APO'DOSIS  (aTTodoats,  a  giving  back). 
A  term  employed  in  Rhetoric  to  denote 
the  consequent  proposition,  as  opposed  to 
C5 


APP 


APP 


protasis,  which  is  the  hypothetical  or 
limiting  clause  of  a  period. 

A'POGEE  (dTz-6,  from,  tf,  the  earth). 
That  point  of  the  moon's  orbit  in  which 
she  is  furthest  from  the  earth.  Her 
perigee  is  that  in  which  she  is  nearest  to 
the  earth.  Formerly,  when  the  earth 
was  considered  as  the  centre  of  the  sys- 
tem, the  terms  apogee  and  perigee  were 
applicable  to  the  places  of  all  the  planets, 
and  also  of  the  sun,  with  respect  to  their 
variable  distances  from  the  earth  ;  but 
now  they  refer  only  to  the  moon.  What 
was  then  called  the  sun's  apogee  is  now 
the  earth's  aphelion ;  and  the  perigee  of 
the  former  has  become  the  perihelion  of 
the  latter. 

APOPHY'LLITE  (<Wo0t/X\<7>,  to 
strip  off  leaves).  Ichlhyophthalmite,  or 
fish-eye  stone.  A  scarce  mineral,  having 
a  pearly  lustre,  like  the  species  of  felspar 
called  moonstone.  It  is  found  in  the 
iron  mines  of  Uto,  in  Sudermania,  a 
province  of  Sweden.  The  term  is  derived 
from  the  lamellar  structure  of  the  mine- 
ral, and  its  exfoliation  under  the  blow- 
pipe. 

APOPHYSIS  (<W6,  from,  <pia>,  to 
grow).  A  process  of  a  bone,  and  a  part 
of  the  same  bone.  An  unequal  expan- 
sion sometimes  found  at  the  base  of  the 
theca  in  mosses. 

A'POSIOPE'SIS  {inroa-iandu),  to  be 
silent  after  speaking).  Literally,  the 
becoming  silent;  a  rhetorical  figure,  by 
which,  for  emphasis  or  modesty,  the 
sentence  is  broken  off,  as  in  Virgil,  JEn. 
I.  135.  The  aposiopesis  is  expressed,  in 
writing,  by  a  short  horizontal  line  at  the 
point  where  the  sense  is  broken  off. 

APOSTASIA'CEjE.  An  order  of  Di- 
cotyledonous plants,  named  from  the 
genus  Aposlaaia,  and  closely  allied  to  the 
Orchidaceae,  from  which  they  differ  essen- 
tially in  having  a  3-celled  fruit,  with 
loculicidal  dehiscence,  and  in  the  style 
being  altogether  free  from  the  stamens 
for  the  principal  part  of  its  length. 

APOTHE'CIA  (utto,  from,  fHjifa  a  cap- 
sule). Scutella,  or  little  shields ;  a  term 
applied,  in  Botany,  to  the  reproductive 
Jfc      organs  of  lichens. 

APPA'RENT  {appareo,  to  appear).  A 
term  applied  in  Astronomy  to  those  phe- 
nomena which  are  actually  observed,  as 
distinguished  from  real  or  true  pheno- 
mena, which  result  from  correction  or 
reduction.  Thus,  the  apparent  altitude 
of  a  star  requires  a  correction  for  refrac- 
tion ;  the  apparent  place  of  a  planet 
requires  a  reduction  to  that  place  in 
34 


which  it  would  be  seen  from  the  centre 
of  the  earth. 

1 .  Apparent  diameter  of  a  planet.  The 
angle  made  by  two  lines  drawn  to  the 
eye  from  the  opposite  points  of  the  planet's 
disk.  The  true  diameter  is  the  line  which 
joins  the  opposite  points  of  the  disk 
itself. 

2.  Apparent  horizon.  The  sensible 
horizon,  or  the  plane  in  which  lies  the 
circle  which  actually  bounds  our  view. 
The  real  or  rational  horizon  is  a  plane 
parallel  to  the  preceding,  drawn  through 
the  centre  of  the  earth. 

3.  Apparent  magnitude.  The  angle 
under  which  any  line  appears  at  the  eye ; 
that  is,  the  angle  made  by  lines  drawn 
from  its  extremities  to  the  eye. 

4.  Apparent  motion.  The  velocity  and 
direction  in  which  a  body  appears  to 
move,  when  the  spectator  is  himself  un- 
consciously in  motion. 

APPENDI'CULATE  {appendicular  a 
little  appendage).  That  which  has  small 
appendages,  as  applied  in  botany  to  the 
calyx  of  Scutellaria. 

APPE'NDIX  (appendo,  to  hang  to). 
An  appendage ;  a  process  appended  to 
any  part  of  a  body,  without  being  essen- 
tial to  the  existence  of  the  body,  as  a 
thorn  or  gland  in  plants. 

A'PPETENCY  {appeto,  to  seek).  The 
disposition  of  organized  beings  to  acquire 
and  appropriate  substances  adapted  to 
their  support. 

APPOSITION  {appono,  to  place  near). 
That  part  of  the  function  of  nutrition, 
by  which  the  constituents  of  the  blood 
are  transformed  on  the  free  surface  of  an 
organ  into  a  solid  unorganized  substance, 
which  is  the  mode  of  growth  of  the  non- 
vascular tissues.     See  Transformations. 

APPREHE'NSION,  SIMPLE.  In  lo- 
gic, that  act  or  condition  of  the  mind,  in 
which  it  receives  a  notion  of  any  object. 
It  is  analogous  to  the  perception  of  the 
senses.  Incomplex  apprehension  regards 
one  object,  or  several  without  any  rela- 
tion being  perceived  between  them,  as  a 
man,  a  card,  &c  Complex  apprehension 
regards  several  objects  with  such  a  rela- 
tion, as  a  man  on  horseback,  a  pack  of 
cards,  &c. 

APPROXIMATION  {ad,  to,  proxi- 
mus,  nearest).  A  result  in  experimental 
philosophy,  which  approaches  more  or 
less  near  to  the  truth,  as  the  calculation 
of  the  distance,  or  of  the  diameter,  of  a 
celestial  body.  In  mathematics,  quan- 
tities are  said  to  be  approximate,  which 
are  nearly,  but  not  absolutely,  equal. 


'       "  Y 


A~2*^^ 


AQU 

APPU'LSE  {appello,  to  drive  to).  The 
near  approach  of  two  celestial  bodies  to 
each  other  in  angular  distance,  so  as  to 
be  seen,  for  instance,  within  the  field  of 
a  telescope. 

APRIO'RI.  A  POSTERIO'RI.  Terms 
expressive  of  two  different  modes  of  rea- 
soning. By  the  argument  a  priori,  a 
conclusion  is  drawn  from  an  antecedent 
fact,  whether  the  consequence  be  in  the 
order  of  time,  or  in  the  necessary  rela- 
tion of  cause  and  effect.  By  the  argu- 
ment a  posteriori,  we  reason  from  what 
is  consequent  in  the  order  of  time  to 
what  is  antecedent,  or  from  effect  to 
cause.  An  individual  may  fall  under 
suspicion  of  murder  for  two  reasons  :  he 
may  have  coveted  the  deceased's  pro- 
perty, or  he  may  be  found  with  it  in  his 
possession  ;  the  former  is  an  a  priori,  the 
latter  an  a  posteriori  argument  against 
him. 

A'PSIDES  (a^/r,  a  curved  link  of  a 
chain).  Apses.  Those  points  in  a  planet's 
orbit,  in  which  it  is  at  its  greatest  or  least 
distance  from  the  sun  or  earth.  The 
line  joining  them,  and  passing  through 
the  sun's  or  the  earth's  centre,  is  called 
the  line  of  the  apsides.  This  term  occa- 
sionally coincides  with  other  terms. 
Thus,  in  the  orbit  of  the  earth,  or  of  any 
primary  planet,  its  higher  apsis  is  also  its 
aphelion,  its  lower  apsis  its  perihelion  ;  in 
the  moon's  orbit,  the  higher  apsis  is  equi- 
valent to  the  apogee,  the  lower  apsis  to 
the  perigee. 

A'PTERA  (a,  priv.,  irrepov,  a  wing). 
A  series  of  insects  characterized  by  the 
absence  of  wings.  Some  of  these  do  not 
undergo  metamorphosis ;  these  compose 
the  orders  thysanoura  and  parasita,  while 
those  which  undergo  this  change,  form 
the  order  syphonaptera. 

A'PUS  (a7roi»?,  without  feet).  Avis  In- 
dica.  Bird  of  Paradise;  a  constellation 
in  the  southern  hemisphere,  consisting 
of  eleven  stars.  The  bird  of  Paradise 
was  formerly  supposed  to  have  no  feet. 

A'PYROUS  (a,  priv.,  ttZp,  fire).  A 
term  applied  to  bodies  which  sustain  the 
action  of  a  strong  heat  for  a  long  time 
without  change  of  figure  or  other  proper- 
ties.    It  is  synonymous  with  refractory. 

AQUA  FORTIS.  An  impure  nitric 
acid,  distinguished  by  the  terms  double 
and  single,  the  latter  having  only  half 
the  strength  of  the  former.  The  more 
concentrated  acid,  which  ismuch  stronger 
than  the  double  aqua  fortis,  is  called  by 
artists  spirit  of  nitre. 

AQUA  MARINE.  A  designation  of 
35 


A  R  A 

beryl,  a  mineral  of  a  green  colour  of 
various  shades,  also  called  greenish- 
yellow  emerald. 

AQUA  REG  I  A.  Royal  water  ;  an  al- 
chemical designation  of  nitro-muriatic 
acid,  from  its  property  of  dissolving  gold, 
the  king  of  metals. 

AQUA'RIUS.  The  eleventh  of  the 
zodiacal  constellations,  consisting  of  108 
stars,  the  principal  of  which  is  Scheat. 
It  presided  over  the  second  month  of 
summer,  and  extended  from  the  20th  of 
July  to  the  20th  of  August.  The  inun- 
dation of  the  Nile  increases  during  this 
month. 

A'QUEOUS  {aqua,  water).  A  term 
synonymous  with  hydrate,  and  employed 
for  expressing  definite  combinations  with 
water.  It  admits  of  prefixes,  as  Jin- 
aqueous,  when  two  atoms  of  water  enter 
into  a  compound. 

A'QUEOUS  ROCKS.  A  term  applied 
in  geology  to  rocks  of  the  second  and 
third  classes,  as  composed  of  matter  de- 
posited by  water.  Those  of  the  second 
class  are  more  especially  named  meta- 
morphic,  from  the  supposition  of  their 
having  undergone  a  remarkaole  change 
in  the  course  of  their  formation.  Aque- 
ous rocks  are  likewise  called  stratified,  as 
being  invariably  found  in  strata  or  layers. 

AQUIFOLIA'CE^.  The  Holly  tribe 
of  Dicotyledonous  plants,  named  from 
the  typical  genus  aquifolium.  Trees  or 
shrubs,  with  leaves  alternate  or  opposite, 
coriaceous ;  corolla  4  or  5-parted,  hypo- 
gynous;  ovary  fleshy,  superior,  2-4-celled; 
fruit  fleshy,  indehiscent,  with  2  to  6  stones. 

A'QUILA.  The  Eagle;  a  northern 
constellation,  containing  (with  Antinous) 
seventy-one  stars,  the  principal  of  which 
is  Altan. 

AQUILARIA'CEjE.  The  Agallochum 
tribe  of  Dicotyledonous  plants,  named 
from  the  typical  genus  aquilaria.  Trees 
with  leaves  alternate  ;  calyx  turbinate  or 
tubular;  stamens  10  or  5;  ovary  supe- 
rior; capsule  pear-shaped,  1-celled,  2- 
valved. 

AQUITE'LjE  {aqua,  water,  tela,  a 
web).  A  family  of  spiders,  which  spread 
their  silken  filaments  under  water,  to  en- 
trap aquatic  insects. 

A'RA.  The  Altar  ;  a  southern  con- 
stellation, containing  nine  stars. 

ARA'CEjE.  Aroidece.  The  Arum  tribe 
of  Monocotyledonous  plants.  Herbace- 
ous plants  with  leaves  sheathing  at  the 
base ;  flowers  unisexual,  arranged  upon 
a  spadix,  within  a  spathe ;  stamens  hypo- 
gynous;  ovary  superior;  fruit  succulent. 
C6 


AR  A 

ARACHNI'DA  (aPaXvr],  a  spider).  A 
class  of  the  Articulata,  or  the  Diplo- 
gangliata  of  Grant,  comprising,  arti- 
culated animals,  generally  with  four 
pairs  of  legs,  without  wings  or  meta- 
morphosis, as  the  spiders,  mites,  and 
scorpions.  They  are  divided,  by  the  dif- 
ference of  their  respiratory  organs,  into 

1.  Tracheata,  which  breathe  by  rami- 
fied tracheae,  as  the  phalangium,  in 
which  there  are  only  two  abdominal  stig- 
mata ;  and 

2.  Pulmonata,  which  breathe  by  pul- 
monary sacs  opening  by  2-8  transverse 
abdominal  stigmata,  as  in  the  scorpions 
and  spiders. 

ARiEO'METER  (iptuor,  thin,  /uexpoi/, 
measure).  An  instrument,  also  called  a 
hydrometer  or  gravimeter,  for  ascertain- 
ing the  specific  gravities  of  bodies,  by  the 
depth  to  which  it  sinks  in  these  bodies, 
the  amount  being  shown  either  by 
weights,  or  by  a  scale  attached  to  it. 
Hence  they  are  distinguished  as  weight 
and  scale  araeometers,  the  former  being 
used  chiefly  for  finding  the  specific  gravity 
of  solids  and  fluids,  whilst  the  latter 
serve  only  for  finding  that  of  fluids,  after 
which,  indeed,  they  are  frequently  named. 

Per  Cent.  Araeometer.  An  araeometer 
made  for  particular  and  mixed  liquors, 
in  which  the  scale  is  so  graduated  as  to 
express  the  component  parts  per  cent., 
either  by  weight  or  volume.  It  is  named 
after  the  fluid  it  is  used  to  test,  as  spirit 
of  wine  araeometer,  beer  araeometer.  To 
this  class  belongs  the  powder  araeometer, 
for  ascertaining  the  proportion  per  cent, 
of  saltpetre  in  gunpowder. 

ARALIA'CEiE.  The  Aralia  tribe  of 
Dicotyledonous  plants.  Trees,  shrubs,  or 
herbs,  with,  in  all  respects,  the  habit  of 
Umbelliferae,  from  which  they  are  dis- 
tinguished chiefly  by  their  many-celled 
fruit  and  more  shrubby  habit. 

ARANEI'DiE  {aranea,  a  spider).  A 
section  of  the  Arachnida,  including  the 
Spiders,  which  are  distinguished  by  hav- 
ing the  abdomen  furnished  with  spin- 
nerets, by  means  of  which  these  animals 
manufacture  silken  filaments  for  the 
construction  of  their  web. 

ARA'NEIFO'RMES  {aranea,  a  spider, 
forma,  likeness).  An  order  of  edentulous 
crustaceous  animals,  in  which  the  extre- 
mities are  rod-like,  long,  and  adapted  for 
walking. 

ARA'NGOES.      A    species    of   beads 
made  of  rough  carnelian,  formerly  im- 
ported from  Bombay,  for  re-exportation 
to  Africa. 
36 


ARC 

A'RBOR.  A  term  fancifully  applied 
to  certain  arborescent  forms  assumed  by 
metals  under  particular  circumstances  : 
thus  arbor  Dianas  signifies  silver,  when 
precipitated  from  its  oxide  in  the  metallic 
form  by  mercury;  arbor  Saturni  denotes 
lead,  when  separated  from  its  salts  in  a 
metallic  state  by  zinc. 

ARBORE'SCENT  (arbor,  a  tree). 
Having  the  characters  of  a  tree,  as  dis- 
tinguished from  those  of  a  shrub  or 
herb. 

ARC  (arcus,  a  bow).  A  portion  of  a 
curved  line  or  circle.  Thus  the  latitude 
and  declination  are  arcs  of  the  meridian, 
and  the  longitude  is  the  arc  of  the 
equator  or  parallel  circle. 

1.  Arc  of  direction.  The  arc  which 
a  planet  appears  to  describe,  when  its 
motion  is  direct  or  progressive. 

2.  Arc  of  retro  gradation.  The  arc 
which  a  planet  describes  whilst  moving 
contrary  to  the  order  of  the  signs,  or 
from  east  to  west. 

A'RCAD^E.  Arch-shells  ;  a  family  of 
the  atrachian  bivalves,  named  from  the 
typical  genus  area,  in  which  the  shell  is 
of  various  shapes,  but  the  valves  close 
all  round. 

ARCA'NUM.  A  secret ;  a  secret  re- 
medy, as  arcanum  duplicatum,  an  old 
name  for  sulphate  of  potash ;  arcanum 
tartari,  deutoxide  of  mercury,  &c.  The 
philosophers'  stone  was  named  by  the 
alchemists  area  arcanorum,  a  chest  of 
secrets. 

ARCHjE'US  {upxh>  beginning).  A  hy- 
pothetical intelligent  agent,  adopted  by 
Van  Helmont,  resembling  the  anima  of 
Stahl.     See,  Anima. 

A'RCHIL.  A  violet  red  paste,  pre- 
pared from  the  lichen  Parmelia,  or  Roc- 
cella,  and  used  in  dyeing.  The  plant, 
reduced  to  a  pulp,  and  treated  with  im- 
pure ammoniacal  liquor,  yields  a  rich 
purple  tincture,  called  litmus,  or  turn- 
sole, used  in  chemistry  as  a  test. 

ARCHIME'DES'  SCREW.  An  ap- 
paratus employed  by  Archimedes  for 
raising  water  and  draining  land  in  Egypt. 
It  consists  of  a  large  tube,  coiled  round 
a  shaft  of  wood,  to  keep  it  in  place  and 
give  it  support.  Both  ends  of  the  tube 
are  open,  the  lower  one  being  dipped  into 
the  water  to  be  raised,  and  the  upper  one 
discharging  it  in  an  intermitting  stream. 
The  shaft  turns  on  a  support  at  each  end, 
the  upper  support  being  elevated  in  the 
air,  the  lower  being  hidden  beneath  the 
water. 

ARCHIPE'LAGO.      A  general  term 


ARG 


A  RG 


applied  to  a  cluster  of  islands,  especially 
to  those  lying  between  the  shores  of 
Greece  and  Asia  Minor.  The  term  is 
perhaps  derived  from  A'ijetov  ireXayos, 
uEgceum  pelagus,  the  iEgean  sea. 

A'RCTIC  CIRCLE  (&pkto?,  a  hear). 
An  imaginary  line  extending  round  the 
North  Pole,  66^  degrees  from  the  equator, 
and  parallel  to  it.  This,  and  the  Antarc- 
tic circ'e,  are  called  the  polar  circles. 

A'RCTIC  CURRENT.  A  current  in 
the  North  Atlantic,  which  seems  to  ori- 
ginate in  the  extensive  masses  of  ice 
surrounding  the  North  Pole,  runs  down 
along  the  eastern  shores  of  Greenland, 
doubles  the  Cape,  and  runs  up  the  west- 
ern coast  of  Greenland,  crosses  Davis's 
Strait,  follows  the  coast  of  Labrador,  runs 
to  the  east  of  Newfoundland,  and  even- 
tually joins  the  gulf  stream  between  43° 
and  47°  of  longitude. 

A'RCTIC  POLE  (aPKTOp,  a  bear).  A 
designation  of  the  North  Pole  of  the 
earth,  from  its  pointing  to  the  constella- 
tions of  the  Great  and  Little  Bears. 

ARCTU'RUS  or  a  BOO'TES  (fyenw, 
the  bear,  ovpa,  the  tail).  A  star  of  the 
first  magnitude  in  the  northern  constel- 
lation Bootes.  It  is  nearly  in  a  right 
line  drawn  through  the  two  hinder  stars 
in  the  tail  of  the  Bear. 

A'RCUATE  (arcus,  a  bow).  Curved 
or  arched ;  a  term  applied,  in  Botany,  to 
any  thing  bent  like  the  arc  of  a  circle,  as 
the  legume  of  medicago  falcata,  the  em- 
bryo of  certain  plants,  &c. 

A'RDEIDjE  (ardea,  the  heron).  The 
Heron  tribe ;  a  family  of  the  Grallatores, 
or  wading  birds,  including  the  herons, 
cranes,  and  storks,  in  which  the  beak  is 
long,  thick,  and  stout,  usually  with  cut- 
ting edges  as  well  as  a  point. 

A'REA.  The  Roman  area  was  a 
threshing-floor ;  but  the  term  is  em- 
ployed by  geometricians  to  denote  any 
superficies  or  surface  of  a  determinate 
extent,  and  is  applied  exclusively  to 
plane  figures. 

A'REOLATE  {areola,  a  little  space). 
Divided  into  areola?  or  small  spaces,  as 
applied  to  surfaces. 

ARFWE'DSONITE.  A  ferruginous 
variety  of  hornblende,  named  from  Arf- 
wedson. 

A'RGAL.  Wine-stone.  Crude  tartar; 
an  acidulous  concrete  salt,  deposited  on 
the  interior  of  wine-casks,  and  used  by 
dyers  as  a  mordant.  On  being  purified, 
it  is  called  cream  or  crystals  of  tartar. 

ARGAND  LAMP.  A  lamp  with  a 
hollow  wick,  for  furnishing  a  rapid  sup- 
37 


ply  of  air  to  the  interior  as  well  as  to  the 
exterior  of  the  flame.  It  is  named  from 
its  inventor,  who  was  a  native  of  France. 

ARGILLA'CEOUS  EARTH.  Argilla. 
White  clay,  or  potters'  earth;  the  earth 
or  clay,  called  by  chemists  alumina, 
from  its  being  obtained  in  its  greatest 
purity  from  alum. 

ARGILLA'CEOUS  ROCKS  {argilla, 
clay).  Homogeneous  soft  substances, 
composed  chiefly  of  aluminous  earth,  or 
clay.  They  comprise  the  shale  or  slate- 
clay,  bituminous  shale,  clay,  and  marl. 

ARGI'LLITE  {argilla,  *clay).  Argil- 
laceous schist,  or  clayslate;  a  mineral 
abundantly  distributed  in  both  primitive 
and  transition  mountains. 

ARGO  NAVIS.  The  Ship  ;  a  southern 
constellation,  containing  sixty-four  stars, 
the  principal  of  which  is  Canopus. 

A'RGUMENT.  In  Logic,  an  expres- 
sion in  which,  M  from  something  laid 
down  and  granted  as  true  {the  premises), 
something  else  {the  conclusion)  beyond 
this  must  be  admitted  to  be  true,  as  fol- 
lowing necessarily  from  the  other." 

I.  The  term  Argument,  in  ordinary 
discourse,  has  several  meanings.  1.  It 
is  very  often  used  for  the  premises  alone, 
in  contradistinction  to  the  conclusion ; 
e.g.,  "the  conclusion  which  this  argu- 
ment is  intended  to  establish  is  so  and 
so."  2.  It  is  sometimes  employed  to  de- 
note what  is,  strictly  speaking,  a  course 
or  series  of  such  arguments,  as  when  it 
is  applied  to  an  entire  dissertation. 
3.  Sometimes  it  signifies  a  disputation, 
or  two  trains  of  argument,  opposed  to 
each  other.  4.  Lastly,  the  various  forms 
of  stating  an  argument  are  sometimes 
spoken  of  as  different  kinds  of  argument, 
as  if  the  same  argument  were  not  capable 
of  being  stated  in  various  ways. — Whately. 

II.  The  term  Argument,  in  astronomical 
tables,  denotes  the  angle  or  quantity  on 
which  a  series  of  numbers  depends.  If, 
for  instance,  a  table  were  formed  of  the 
sun's  declination,  corresponding  to  every 
degree,  &c,  of  longitude,  so  that,  the  longi- 
tude being  known,  the  declination  might 
be  found  opposite  to  it  in  the  table,  the 
longitude  would  then  be  called  the  argu- 
ment of  the  declination,  and  the  table  would 
be  said  to  be  entered  with  the  argument. 

ARGUME'NTUM  AD  HOMINEM. 
A  form  of  argument,  described  by  logi- 
cians, in  which  the  conclusion  actually 
established  is  not  the  absolute  and  gene- 
ral one  in  question,  but  relative  and  par- 
ticular; viz.,  not  that  "such  and  such  is 
the  fact,"  but  that  "  this  man  is  bound  to 


AR1 


ARS 


admit  it,  in  conformity  to  his  principles 
of  reasoning,  or  in  consistency  with  his 
own  conduct,  situation,"  &c. 

1.  The  argumentum  ad  hominem,  in 
the  popular  but  less  scientific  sense,  "  is 
addressed  to  the  peculiar  circumstances, 
character,  avowed  opinions,  or  past  con- 
duct of  the  individual,  and  therefore  has 
a  reference  to  him  only,  and  does  not 
bear  directly  and  absolutely  on  the  real 
question,  as  the  argumentum  ad  rem  does. 

2.  "The  argumentum  ad  verecundiam, 
in  like  manner,  is  described  as  an  appeal 
to  our  reverence  to  some  respected  au- 
thority, some  venerable  institution,  &c. ; 
and  the  argumentum  ad  populum,  as  an 
appeal  to  the  prejudices,  passions,  &c,  of 
the  multitude. 

3.  "The  argumentum  ad  ignorantiam 
is  usually  enumerated  with  these,  but  is 
evidently  nothing  more  than  the  employ- 
ment of  some  kind  of  fallacy,  in  the 
widest  sense  of  that  word,  towards  such 
as  are  likely  to  be  deceived  by  it." 

A'RIES.  A  zodiacal  constellation  of 
rixed  stars,  drawn  on  the  globe  in  the 
figure  of  a  ram.  It  is  the  first  of  the 
twelve  signs  of  the  zodiac,  from  which  a 
twelfth  part  of  the  ecliptic  takes  its 
name.  It  indicates  the  first  month  of 
autumn,  extending  from  the  20th  of  Sep- 
tember to  the  20th  of  October.  It  con- 
sists of  66  stars. 

A'RIETIS.  A  star  of  the  second 
magnitude,  in  the  head  of  the  Ram. 

ARI'LLUS.  A  term  applied,  in  Bo- 
tany, to  an  expansion  of  the  placenta,  or 
funiculus,  about  the  seed :  the  mace  of 
the  nutmeg,  and  the  red  covering  of  the 
seed  of  the  spindle-tree,  are  instances. 

ARI'STOLOCHIA'CEjE  (aP«<TTov,  the 
best,  Xoxeia,  delivery).  The  Birthwort 
tribe  of  Dicotyledonous  plants,  so  named 
from  the  reputed  emmenagogue  proper- 
ties of  the  genus  Aristolochia.  Herba- 
ceous plants  or  shrubs,  with  leaves  alter- 
nate; flowers  apetalous,  hermaphrodite; 
stamens  epigynous  ;  ovary  many-celled; 
fruit  dry  or  succulent,  many-celled. 

ARITHMETIC  {apt0/jLo?,  number). 
The  science  which  treats  of  numbers,  of 
the  mode  of  expressing  them,  of  the 
manner  of  computing  by  them,  and  of 
the  various  uses  to  which  they  are  ap- 
plied in  the  practical  business  of  life. 

1.  Arithmetical  Complement.  That 
which  a  number  wants  of  the  next  high- 
est decimal  denomination.  Thus,  what 
7  wants  of  10,  viz.  3;  what  32  wants  of 
100,  viz.  68;  what  159  wants  of  1000, 
viz.  841 ;  or  .017  of  1,  viz.  .983  ;  are  the 


arithmetical  complements  of  these  num- 
bers. 

2.  Arithmetical  Mean.  That  number 
or  fraction  which  is  intermediate  between 
two  other  numbers,  as  10  between  6  and 
14;  10£  between  4  and  17.  To  find  the 
arithmetical  mean,  take  the  half  sum  of 
the  two  numbers. 

A'RMATURE  (armatura,  armour).  A 
term,  in  its  general  sense,  denoting 
armour.  A  natural  magnet  is,  however, 
said  to  have  an  armature,  or  to  be  armed, 
when  its  two  poles  are  polished  and 
covered  over  with  smooth  plates  of  iron, 
which  terminate  in  two  strong  projecting 
ends.  The  magnetic  power,  imparted  by 
this  means  to  the  two  iron  plates,  is  con- 
centrated in  the  knobs,  and  thus  a  north 
and  a  south  pole  are  made. 

A'RMILLARY  SPHERE  {armilla,  a 
bracelet).  A  hollow  sphere,  representing 
the  several  circles  of  the  globe  :  it  is  so 
constructed  that  all  the  surface  of  the 
sphere  is  cut  away,  except  the  equator, 
ecliptic,  colures,  &c.     See  Astrolabe. 

A'RQUIFOUX.  A  lead  ore,  commonly 
called  potters'  ore,  from  its  being  used  by 
potters  as  a  green  varnish. 

A'RRAGONITE.  An  impure  species 
of  carbonate  of  lime,  found  in  Arragon 
in  Spain.  It  occurs  in  the  form  of  fibrous 
branches,  which  ramify  from  a  centre, 
called  fios  ferri,  or  iron-flower. 

ARROW-HEADED  CHARACTERS. 
A  term  applied  to  certain  marks  stamped 
on  the  bricks  of  Babylon,  and  cut  on  the 
marble  monuments  at  Persepolis.  Their 
character  is  formed  from  the  isosceles  tri- 
angle or  wedge,  and  hence  they  are  termed 
in  'Latin  cuneiformes,  or  wedge-shaped. 

A'RSENIC  {apaeviKov,  masculine;  an 
old  epithet,  denoting  powerful  properties). 
A  bluish-white  metal,  of  great  brilliancy, 
resembling  steel.  The  arsenic  of  com- 
merce, commonly  called  white  arsenic, 
and  known  as  a  violent  poison,  is  arse- 
nious  acid.  The  fuming  liquor  of  arsenic 
is  the  sesquichloride,  a  colourless  volatile 
fluid,  which  fumes  strongly  on  exposure 
to  the  air.  Realgar,  also  called  ruby,  or 
red  arsenic,  is  the  protosulphuret.  Orpi- 
ment,  or  yellow  arsenic,  is  the  sesquisul- 
phuret,  and  constitutes  the  colouring 
principle  of  the  pigment  called  king's 
yellow.  Another  well-known  pigment, 
called  Scheele's  mineral  green,  consists  of 
an  arsenite  of  copper.  On  exposing  the 
metal  to  a  moist  atmosphere,  a  black 
powder  is  obtained,  called  poudre  a 
mouches,  or  fly-powder.  Lastly,  a  solu- 
tion of  arsenic  in  muriatic  acid,  heated 


ART 


ASC 


and  condensed,  sublimes  into  a  thick 
liquid,  formerly  called  butter  of  arsenic. 

ARSE'NICAL  MINERALS.  A  class 
of  minerals  in  which  arsenic  acts  the 
part  of  the  electro  negative  element. 
They  occur  in  primitive  districts,  and 
are  usually  associated  with  metallic  sul- 
phurets. 

A'RSENOVI'NIC  ACID.  An  acid  pro- 
duced by  the  action  of  arsenic  upon  alcohol. 

A'RSIS  and  THE'SIS  (ftp**,  eleva- 
tion; deats,  depression).  Technical  terms 
employed  in  ancient  music  and  ancient 
metrics.  Arsis  denoted  an  elevation  of 
the  voice,  which  is  now  called  metrical 
accentuation.  Thesis  was  a  depression 
of  the  voice,  and  was  opposed  to  arsis. 
In  Music,  the  terms  signified  the  rising 
and  the  falling  of  the  hand  in  beating 
time;  and  hence  the  Latin  word  ictus,  or 
stroke,  corresponded  with  arsis.  Lastly, 
per  arsin  expressed,  in  Music,  a  fall  from 
acute  to  grave ;  per  thesin,  a  rise  from 
grave  to  acute. 

ART  and  SCIENCE.  Art  is  the  ap- 
plication of  knowledge  to  practical  pur- 
poses. Science  is  a  knowledge  of  the 
principles  of  art.  If  the  knowledge  be 
merely  accumulated  experience,  its  ap- 
plication is  empirical  art;  but  if  it  be 
experience  reasoned  upon  and  brought 
under  general  principles,  it  assumes  a 
higher  character,  and  becomes  a  scientific 
art. 

ARTE'RIALIZA'TION.  The  conver- 
sion of  the  venous  into  the  arterial  blood, 
during  its  passage  through  the  lungs, 
by  the  extrication  of  carbonic  acid,  and 
the  absorption  of  oxygen  from  the  air. 

ARTE'SIAN  WELL.  A  perpendicu- 
lar perforation  of  the  crust  of  the  earth, 
of  small  diameter  and  of  great  depth, 
through  which  water  rises  to  the  surface 
by  an  artificial  jet.  The  term  is  derived 
from  Artesium,  or  Artois,  where  con- 
siderable attention  has  been  paid  to  this 
means  of  procuring  water. 

ARTHRO'DIAL  (ZpOpov,  a  joint). 
Belonging  to  a  joint,  but  restricted  to 
that  form  of  joint  in  which  a  ball  is  re- 
ceived into  a  shallow  cup,  commonly 
called  the  ball-and-socket  joint. 

A'RTICLE  {articulus,  a  joint).  The 
name  given  by  grammarians  to  two 
words,  a  or  an,  and  the,  which  are  pre- 
fixed to '  substantives  for  the  purpose  of 
showing  whether  they  are  used  in  a 
general  sense  or  in  particular  relation  to 
an  individual.  An  is  a  corruption  of  one, 
and  a  is  a  greater  corruption  of  the  same 
adjective.  The  appears  to  be  derived 
39 


from  the  Greek  to,  through  the  Gothic 
sa  or  tha,  and  thence  through  the  German 
der  or  the  Dutch  de. 

A'RTICULA'TA  (articulus,  a  joint). 
Articulated  or  jointed  animals ;  one  of 
Cuvier's  four  great  divisions  of  the  Ani- 
mal Kingdom,  in  which  the  skeleton, 
which  is  external,  is  formed  of  numerous 
pieces  or  segments,  jointed  or  articulated 
together,  as  in  the  lobster,  the  centi- 
pede, &c.  This  division  corresponds 
with  the  Annulosa  of  Macleay,  the 
Homogangliata  of  Owen,  and  the  Diplo- 
neura  of  Grant. 

ARTOCA'RPE^E.  The  Artocarpus, 
or  Bread-fruit  tribe  of  Dicotyledonous 
plants ;  a  division  of  the  Urticaceae,  or 
Nettle  tribe,  distinguished  by  their  con- 
solidated flowers  and  milky  juice. 

ASBE'STOS  (a,  priv.,  cfiewvut,  to 
extinguish).  A  mineral  substance,  of  a 
fibrous  structure,  from  which  an  incom- 
bustible linen  is  made.  There  are  several 
varieties,  all  more  or  less  flexible  and 
fibrous,  and  termed  common  asbestos, 
amianthus,  mountain  leather  and  paper, 
and  mountain  wood. 

ASCENDING  SIGNS.  The  signs  are 
said  to  be  ascending,  when  they  are  east- 
ward from  the  meridian,  and  are,  con- 
sequently, approaching  the  meridian 
through  the  effect  of  the  diurnal  rotation 
of  the  earth. 

ASCE'NSION,  RIGHT  (ascendo,  to 
rise).  An  astronomical  term,  applied  to 
those  arcs  in  the  heavens  which  corre- 
spond to  longitudes  on  the  earth.  Hence 
the  right  ascension  of  a  star  denotes  the 
arc  of  the  equator  intercepted  between 
the  first  point  of  Aries  and  that  point  of 
the  equator  which  comes  to  the  meridian 
at  the  same  instant  with  the  star. 

1.  Oblique  Ascension  is  a  term  nearly 
out  of  use.  It  is  an  extension  of  the 
right  ascension  to  the  oblique  sphere,  in 
which  one  pole  is  above  the  horizon,  and 
the  other  below  it.  The  oblique  ascen- 
sion of  a  star  is  the  arc  of  the  equator 
intercepted  between  the  vernal  equinox 
and  that  point  of  the  equator  which 
comes  to  the  horizon  at  the  same  time 
with  the  star. 

2.  Ascensional  Difference  is  also  a  term 
nearly  out  of  use.  It  denotes  the  dif- 
ference between  the  oblique  and  the  right 
ascensions,  and  is  chiefly  used  in  respect 
to  the  sun,  because,  when  the  arc  which 
it  expresses  is  turned  into  time,  it  shows  . 
the  time  before  or  after  six  o'clock  of 
sunrise. 

A'SCI    (daKos,  a  leathern  bag).    The 


ASC 


ASP 


botanical  designation  of  the  sporuliferous 
tubes  imbedded  in  the  nucleus  of  the 
shields  of  lichens. 

ASCI'DIA  (ao-Kof,  a  bottle).  An  order 
of  the  tunicated  Mollusca,  named  from 
their  resemblance  in  shape  to  a  leathern 
bottle.  In  these,  the  two  orifices  ap- 
proach one  another  more  or  less  closely, 
and  the  body  is  either  immediately  fixed 
to  some  solid  mass,  or  attached  to  it  by 
a  foot-stalk.     See  Salpce. 

ASCIDIOI'DA  {ascidia,  and  eZdor, 
likeness).  An  order  of  the  Polypi- 
pherous  Radia'a,  named  from  their  affi- 
nity to  the  ascidice,  a  group  in  the  lowest 
class  of  Mollusca.  They  have  also  been 
called  bryozoa,  from  their  fancied  re- 
semblance to  mosses,  and  cilio-brachiata, 
from  the  presence  of  cilia  on  their  arms. 

ASCI'DIUM  {dcKibiov,  dim.  of  uo-kos, 
a  leathern  bag).  The  botanical  term  for 
the  pitcher  of  Nepenthes  and  other 
plants,  consisting  in  a  peculiar  modifica- 
tion of  the  leaf,  by  which  the  petiole  is 
dilated  and  hollowed  out  at  its  upper 
end,  and  the  lamina  is  articulated  with 
it  and  closes  its  orifice. 

A'SCII  (a,  not,  awia,  shadow).  A  term 
applied  to  the  inhabitants  of  the  Torrid 
Zone,  because,  the  Sun  being  sometimes 
exactly  vertical  to  them  at  noon,  they 
have  no  shadow  at  all.  At  t^ie  other 
times  of  the  year,  their  noon-shadow 
points  both  northward  and  southward, 
according  to  the  place  of  the  sun,  when 
he  is  not  vertical  to  them  ;  and  hence 
,  they  are  called  Amphiscii,  from  dn<ph, 
on  both  sides,  and  oiua,  shadow, 

1.  Heteroscii  (erepos,  another,  <nud, 
shadow).  A  term  applied  to  the  inha- 
bitants of  the  Temperate  Zones,  from 
their  having  their  shadows,  at  noon, 
always  on  one  side  or  other  of  them,  either 
north  or  south,  according  as  they  may  be 
situated,  throughout  the  whole  year. 

2.  Periscii  (nepi,  around,  anui,  shadow). 
A  term  applied  to  the  inhabitants  of  the 
Frigid  Zones,  because  at  certain  seasons 
of  the  year,  during  many  revolutions  of 
the  earth,  the  sun  does  not  set  at  all  to 
them,  nor  so  much  as  touch  the  horizon, 
and  hence  their  shadows  move  completely 
round  them  once  in  24  hours  ;  and,  in  pro- 
portion as  they  are  nearer  the  Poles,  will 
be  the  greater  continuance  of  the  sun 
above  the  horizon,  for  one,  two,  or,  it 
may  be,  six  months  together. 

3.  To  these  may  be  added  the  Bra- 
chyscii  {ftpaxw,  short),  or  such  as  pro- 
ject short  shadows  at  noon :  the  Ma- 
croscii  (^ua^pof,  long),  who  project  long 

40 


shadows  at  noon ;  and  the  Antiscii  (uvtI, 
opposite),  whose  shadows  are  in  opposite 
directions,  from  their  having  the  sun  on 
opposite  sides. 

4.  The  ancients,  likewise,  distinguished 
the  inhabitants  of  the  earth,  with  respect 
to  their  longitude  and  latitude,  into  the 
Perioeci  {nepl  and  otKof,  habitation),  who 
dwelt  in  the  same  latitude,  but  in  opposite 
longitudes;  the  Antoeci  (ui/ri  and  o'Uos), 
who  dwelt  in  the  same  longitude,  but  in 
opposite  latitudes ;  and  Synoeci  {avv  and 
otKof),  who  lived  in  the  neighbourhood 
of  each  other.  The  Antipodes  had  both 
latitudes  and  longitudes  diametrically 
opposite  to  each  other. 

ASCLEPIADA'CEjE.  The  Asclepias 
tribe  of  Dicotyledonous  plants.  Shrubs 
or  herbaceous  plants,  with  leaves  opposite, 
alternate,  or  whorled ;  corolla  monope- 
talous,  hypogynous ;  stamens  inserted  into 
the  base  of  the  corolla ;  ovaries  two ;  fruit 
one  or  two  follicles. 

ASE'PTIC  (a,  priv.,  o^tto),  to  putrefy). 
A  term  applied  to  substances  which  are 
free  from  the  putrefactive  process. 

ASPA'RAGIN.  A  crystalline  sub- 
stance, formed  spontaneously  in  the  juice 
of  asparagus  which  has  been  evaporated 
to  the  consistence  of  syrup.  It  is  gene- 
rally procured  from  the  root  of  the  marsh- 
mallow. 

ASPA'RAMIDE.  A  principle  dis- 
covered in  the  juice  of  the  asparagus, 
and  in  the  root  of  the  marsh-mallow  and 
liquorice.  It  is  the  agedoite  of  Robiquet, 
and  synonymous  with  asparagin. 

ASPA'RTIC  ACID.  An  acid  obtained 
from  asparagin,  when  boiled  for  some  time 
with  hydrated  oxide  of  lead  or  magnesia. 

A'SPECT.  An  obsolete  astronomical 
term,  applied  to  the  various  positions  of 
the  planets  with  respect  to  one  another, 
as  seen  from  the  earth.  Five  aspects 
have  been  reckoned  :  at  conjunction,  6 , 
two  planets  have  the  same  longitude  ; 
when  sixty  degrees  apart,  the  aspect  is 
sextile,  •*  ;  when  ninety,  quartile,  Q  ; 
when  120,  trine,  A;  when  180  degrees 
apart,  they  are  in  opposition,  £ . 

ASPERGI'LLIFORM  {aspergillus,  a 
brush,  forma,  likeness).  Brush-like;  di- 
vided into  minute  ramifications,  as  the 
stigmas  of  grasses,  certain  hairs  of  the 
cuticle  of  plants,  &c. 

ASPHA'LTENE.  A  solid  black  sub- 
stance, obtained  by  submitting  the  bitu- 
men of  Bechelborum,  purified  by  ether, 
to  a  high  and  prolonged  temperature. 

ASPHA'LTUM  (a<r0a\To?,  asphalt, 
bitumen).   A  black  or  brown,  brittle  sub- 


AST 


ATA 


stance,  also  called  bitumen  Judaicum,  or 
Jews'  pitch,  forming  in  lumps  on  the 
surface  of  some  waters,  especially  near 
Babylon,  and  employed  by  the  Egyptians 
for  embalming,  under  the  name  of  mu- 
mia  mineralis. 

ASPHODE'LEiE.  The  Asphodel  or 
Lily  tribe  of  Monocotyledonous  plants. 
Herbaceous  plants,  with  bulbs,  occa- 
sionally arborescent,  with  leaves  not  arti- 
culated with  the  stem,  parallel-veined ; 
flowers  hexapetaloideous  ;  stamens  hypo- 
gynous  ;  ovary  superior  ;  fruit  succulent 
or  dry  and  capsular. 

ASSA'YING.  The  chemical  operation 
of  ascertaining  the  quantity  of  any  metal 
in  an  ore  or  mixture.  It  differs  from 
Analysis  only  in  degree,  and  is  performed 
in  the  dry  way,  as  by  heat ;  in  the  moist 
way,  as  by  acids  and  other  re-agents ;  or 
by  both  methods.     See  Cupellatiun. 

ASSIMILATION  (assimilo,  to  liken 
to).  The  function  by  which  organized 
bodies  convert  aliment  into  their  own 
proper  substance. 

ASSOCIATE  MOVEMENTS.  Con- 
sensual  Movements.  Those  movements 
which,  contrary  to  our  will,  accompany 
other,  voluntary,  motions.  Thus,  the  eye 
cannot  be  moved  inwards  by  the  action  of 
the  rectus  internus,  without  contraction 
of  the  iris  being  produced. 

ASTA'TIC  (a,  priv.,  arau,  to  stand). 
A  term  applied  to  a  magnetic  needle, 
when  its  directive  property  is  destroyed 
by  the  proximity  of  another  needle  of 
equal  magnetic  intensity,  fixed  parallel 
to  it,  and  in  a  reversed  position,  each 
needle  having  its  north  pole  adjacent  to 
the  south  pole  of  the  other.  In  this  state 
the  needles,  neutralizing  each  other,  are 
unaffected  by  the  magnetism  of  the  earth, 
while  they  are  still  subject  to  the  influence 
of  galvanism. 

ASTE'RIA  (uo-r^p,  a  star).  A  variety 
of  sapphire,  showing  a  star-like  opa- 
lescence in  the  direction  of  the  axis, 
when  cut  round. 

ASTE'RISM  (ua-rJ/p,  a  star).  A  small 
cluster  of  stars,  either  distant  from,  or 
forming  a  part  of,  a  constellation. 

ASTEROI'DA  (uoTqp,  a  star,  eUos, 
likeness).  An  order  of  the  polypipherous 
Radiata,  named  from  the  star-shaped 
form  presented  by  the  tentacula,  when 
expanded^  They  may  be  also  termed 
Alcyonian  polypiphera,  from  the  name  of 
one  of  the  principal  groups. 

A'STEROIDS  (do-rJjp,  a  star,  e?3oc, 
likeness).  A  term  applied  by  Herschel 
to  the  recently  discovered  planets,  Ceres, 
41 


Juno,  Pallas,  and  Vesta,  and  including 
those  celestial  bodies  which  move  in 
orbits  of  any  eccentricity  round  the  sun, 
whatever  angle  their  orbits  make  with 
the  ecliptic,  whether  the  motion  of  these 
bodies  be  direct  or  retrograde,  whether 
they  have  or  have  not  atmospheres. 

ASTRI'NGENT  PRINCIPLE.  A 
principle  existing  in  the  gall-nut  and 
other  substances,  and  characterized  by 
the  property  of  contracting  the  muscular 
fibre.  From  the  use  of  this  principle  in 
tanning  skins,  it  has  been  called  tannin. 

A'STROLABE  (a<rTpo*,  a  star,  \afx- 
/3di/w,  to  take).  Planisphere.  A  pro- 
jection of  the  sphere  upon  the  plane  of 
one  of  the  great  circles :  it  is  furnished 
with  a  graduated  rim,  to  which  sights  are 
added,  for  the  purpose  of  taking  altitudes. 

ASTRO'LOGY  (aarpov,  a  star,  X6yo?, 
an  account).  A  term  strictly  meaning 
the  science  of  the  stars,  but  applied  to 
the  pretended  discovery  of  future  events 
by  means  of  the  position  of  the  heavenly 
bodies. 

ASTRO'NOMY  {'6.<ttPov,  a  star,  vo/jlov, 
a  law).  The  science  which  treats  of  the 
motions,  the  distances,  the  size,  the  phy- 
sical constitution,  the  eclipses,  and  all 
other  phenomena  of  the  heavenly  bodies. 
By  the  term  astra,  the  ancients  under- 
stood not  only  the  stars,  properly  so 
called,  but  also  the  sun,  the  moon,  and 
all  the  bodies  which  compose  the  visible 
universe. 

1.  Descriptive  astronomy  demonstrates 
the  magnitudes,  distances,  and  densities 
of  the  heavenly  bodies,  and  explains 
the  phenomena  dependent  on  their  mo- 
tions, as  the  change  of  seasons,  and  the 
vicissitudes  of  day  and  night. 

2.  Physical  astronomy  explains  the 
theory  of  planetary  motion,  and  the  laws 
by  which  this  motion  is  regulated  and 
sustained. 

3.  Practical  astronomy  details  the  de- 
scription and  use  of  astronomical  in- 
struments, and  develops  the  nature  and 
application  of  astronomical  calculations. 

ASY'MPTOTES  (uav^nnoTos,  that 
which  does  not  fall  with).  A  term  ap- 
plied to  two  lines  (one  of  which,  at  least, 
must  be  a  curve),  which,  although  con- 
tinually approaching  nearer  and  nearer, 
and  although  indefinitely  produced,  never 
meet  each  other.  This  properly  occurs  in 
the  hyperbola,  and  appears  of  a  paradox- 
ical character. 

ATA'CAMITE.  A  native  muriate  of 
copper,  found  in  the  desert  of  Atacama, 
between  Chili  and  Peru.    It  occurs  in  a 


ATM 


ATO 


compact  and  in  an  arenaceous  form  ;  in 
the  latter,  it  is  termed  copper  sand. 

ATHANOR.  An  ancient  kind  of  fur- 
nace, so  constructed  that  the  fire  should 
be  constantly  supplied  with  fuel  in  pro- 
portion to  the  consumption. 

ATHERI'CERA  (u^i/p,  an  ear  of  corn, 
tcppa<;,  a  horn).  A  section  of  Dipterous 
insects,  in  which  the  antennae  have  only 
two  or  three  joints,  the  last  being  fur- 
nished with  a  bristle.  It  includes  the 
Flies,  strictly  so  called,  the  Bot-flies,  &c. 

ATHE'RMANOUS  (a,  priv.,  0<-'pMn, 
heat).  A  term  applied  to  those  sub- 
stances which  retain  all  the  heat  they 
receive,  as  distinguished  from  diather- 
manous  bodies,  which  transmit  all  the 
rays  of  heat  through  their  substance. 

ATMO'METER  (trr/io?,  vapour,  fxerpov, 
measure).  An  instrument  for  measuring 
the  quantity  of  exhalation  from  a  moist 
surface  in  a  given  time. 

A'TMOSPHERE  (aTjuor,  vapour, 
o-(pa7pa,  a  sphere).  That  volume  of  air 
which  surrounds  the  earth.  Its  mean 
height  has  been  estimated  at  from  44  to 
47  miles,  its  volume  as  the  twenty-ninth 
of  that  of  the  globe,  and  its  weight  only 
forty-three  thousandths. 

1.  Atmospheric  Pressurexs  indicated  by 
the  length  of  a  column  of  mercury.  A 
mercurial  column,  30  inches  in  length, 
presses  on  a  given  surface  with  the  same 
force  as  the  atmosphere  in  its  ordinary 
state ;  and  hence  the  force  of  a  60-inch 
column  is  equal  to  the  pressure  of  two 
atmospheres ;  that  of  15  inches,  to  half  an 
atmosphere ;  that  of  one  inch,  to  l-30th  of 
the  atmospheric  pressure. 

2.  Atmospheres— two,  three,  fyc.  Mul- 
tiplied pressures  of  air  arising  from  con- 
densation, the  ordinary  pressure  being 
fifteen  pounds  on  the  square  inch.  Press- 
ures arising  from  other  causes,  as  the 
weight  of  liquids  and  the  force  of  steam, 
are  also  frequently  counted  by  atmo- 
spheres. 

3.  Atmosphere,  refraction  of.  A  term 
expressive  of  the  refraction  of  the  rays 
of  light,  as  they  pass  from  the  celestial 
bodies  into  the  atmosphere,  owing  to  its 
being  denser  than  the  ethereal  or  vacuous 
medium  which  intervenes  between  it  and 
the  celestial  bodies.  This  refraction 
varies  with  the  density  of  the  atmo- 
sphere, and  also  with  the  direction  in 
which  the  rays  enter.  The  atmosphere 
gradually  increases  in  density  from  the 
higher  to  the  lower  strata;  and,  there- 
fore, a  ray  of  light  will  be  more  and  more 
refracted  in  its  passage  to  the  earth's  sur- 

42 


face,  so  as  to  descend  in  a  curved  line. 
The  curve,  too,  varies  with  the  direction 
of  the  ray,  that  coming  from  the  zenith 
alone  being  a  straight  line. 

4.  Atmosphere,  electrical.  The  dis- 
tance at  which  an  electrified  body  is 
capable  of  resolving  the  neutral  electri- 
city of  unelectrified  bodies  into  its  ele- 
ments, when  brought  into  proximity  to 
the  former,  is  termed  the  electrical  at- 
mosphere of  that  body. 

5.  Atmosphere,  magnetic.  The  range 
within  which  a  magnet  exerts  its  influ- 
ence in  any  magnetizable  body  within  a 
certain  distance  of  itself,  is  termed  its 
circle  of  magnetic  influence,  or  its  mag- 
netic atmosphere. 

ATMOSPHERIC  ENGINE.  A  term 
applied  to  the  single-action  steam-engine, 
in  which  only  the  ascent  of  the  piston  is 
effected  by  means  of  steam,  its  descent 
being  mainly  effected  by  the  pressure  of 
the  atmosphere. 

A'TOLLS.  Coral-islands,  or  lagoon- 
islands,  of  an  annular  form,  or  consisting 
of  a  circular  strip  or  ring  of  coral  sur- 
rounding a  central  lagoon. 

A'TOM  (a,  priv.,  re'/ivto,  to  cut).  An 
ultimate  particle  of  matter,  incapable  of 
further  division.  Berzelius  distinguished 
atoms  into  elementary  and  compound. 
The  latter  are  subdivided  into,  1.  Com- 
pound atoms  of  the  first  order,  or  atoms 
formed  of  only  two  elementary  sub- 
stances united;  2.  Organic  atoms,  or 
those  composed  of  more  than  two  ele- 
mentary substances,  and  found  only  in 
organic  bodies,  or  bodies  obtained  by  the 
destruction  of  organic  matter  ;  and, 
3.  Compound  atoms  of  the  second  order, 
or  those  formed  by  the  union  of  two  or 
more  compound  atoms,  as  the  salts. 

ATO'MIC  THEORY.  A  theory  for 
explaining  the  nature  of  matter,  founded 
by  Leucippus.  He  considered  the  basis 
of  all  bodies  to  consist  of  extremely  fine 
particles,  differing  in  form  and  nature, 
which  he  supposed  to  be  dispersed 
throughout  space,  and  to  which  his 
follower  Epicurus  first  gave  the  name  of 
atoms.  To  these  atoms  he  attributed  a 
rectilinear  motion,  in  consequence  of 
which  such  as  are  homogeneous  united, 
whilst  the  lighter  were  dispersed  through- 
out space.     See  Dynamic  Theory. 

ATO'MIC  WEIGHTS.  An  expression 
connected  with  the  theory  that  all  bodies 
consist  of  atoms,  which  are  of  the  same 
size  and  shape  in  the  same  body,  but 
which  differ  in  weight  in  different  bodies. 
The  weight  of  an  atom  of  oxygen  is  eight 


ATT 


AUG 


times  as  great  as  that  of  an  atom  of  hy- 
drogen, and  half  as  great  as  that  of  an 
atom  of  sulphur.  On  this  theory  are 
founded  three  universal  laws  : — 

1.  That  the  parts  by  weight  in  which 
bodies  mutually  combine,  stand  in  a  fixed 
numerical  relation  to  each  other. 

2.  That  in  every  chemical  combination 
the  parts  by  weight  of  one  element  may  be 
represented  by  certain  weights  of  other 
substances. 

3.  That  the  weights  which  mutually 
represent  one  another  at  once  furnish  the 
proportion  in  which  these  equivalent  sub- 
stances combine. 

ATRA'CHIA  (a,  priv.,  Tpaa>,  to  per- 
forate). A  tribe  of  bivalved  Mollusca, 
which  are  destitute  of  siphons  for  im- 
bibing food.     See  Macrotrachia. 

ATRACTE'NCHYMA  ( 'drpaKTos,  a 
spindle,  Zyxvua,  an  infusion).  A  term 
applied  by  some  botanical  writers  to  the 
fusiform,  or  spindle-shaped,  variety  of 
spheroidal  cellular  tissue. 

A'TROPOUS  (a,  priv.,  rpe'Trw,  to  turn). 
That  which  is  not  inverted,  as  applied  in 
Botany  to  the  erect  ovule.  In  this  case, 
the  parts  of  the  ovule  undergo  no  altera- 
tion of  position  during  their  growth,  and 
thus  the  two  sacs  and  the  nucleus  are 
all  connected  at  the  base  of  the  ovule. 
The  term  is  synonymous  with  orthotro- 
pous. 

ATTE'NUATE  {ad,  to,  tenuis,  thin). 
Tapering  ;  gradually  diminishing  in 
oreadth,  and  terminating  in  a  point. 

ATTENUATION  (attenuo,  to  make 
thin).  The  process  by  which  a  fluid 
becomes  of  less  specific  gravity,  as  when 
it  undergoes  fermentation,  and  parts 
with  carbonic  acid. 

ATTRACTION  (attraho,  to  draw  to). 
A  general  term  denoting  the  mutual 
tendency  of  bodies  towards  one  another, 
and  explanatory  of  certain  physical  and 
chemical  properties  of  matter. 

1.  Attraction  of  Cohesion.  The  ten- 
dency of  the  particles  of  bodies  to  cohere, 
and  form  masses.  On  the  degree  of  this 
force  depend  the  three  aggregate  forms  of 
matter,  which  are  distinguished  as  the 
solid,  the  liquid,  the  gaseous.  Cohesion 
is  the  antagonist  of  affinity. 

2.  Attraction  of  Gravitation.  The  mu- 
tual tendency  of  the  masses  of  bodies 
towards  one  another.  Universal  gravi- 
tation relates  to  the  mutual  action  of  the 
celestial  bodies  on  each  other  and  the 
pravitation  of  our  earth  ;  terrestrial 
gravity  relates  to  the  mutual  operation  of 
terrestrial  objects,  or  to  the  effects  which 

43 


the  earth  produces  on  all  bodies  more 
immediately  connected  with  it.  Cohesion 
operates  at  sensible,  gravitation  at  insen- 
sible distances. 

3.  Attraction  of  Affinity.  The  tendency 
of  the  atoms  of  dissimilar  bodies  to  com- 
bine and  form  chemical  compounds. 
This  force  effects  the  combination  and 
decomposition  of  dissimilar  bodies,  with 
the  production  of  individual  properties 
distinct  from  those  which  they  had  in 
their  former  state.     See  Affinity. 

4.  Attraction,  Capillary.  The  power 
by  which  a  liquid  ascends  in  the  interior 
of  a  capillary  tube,  or  tube  of  small  bore, 
above  the  surface  of  the  liquid  which 
surrounds  it.  The  phenomenon  occurs 
in  solid  bodies  which  are  capable  of  being 
wetted. 

5.  Attraction,  Superficial.  A  term 
sometimes  applied  to  that  modification 
of  the  adhesion  of  bodies  which  is  caused 
not  merely  by  the  mass  of  bodies,  but 
also  by  the  number  of  points  of  contact, 
or  the  extent  of  their  touching  surfaces. 

6.  Attraction,  Electrical.  The  force 
which  is  exhibited  in  the  tendency  of  the 
free  positive  and  negative  electricities  to 
regain  their  equilibrium  by  combination 
each  with  its  antagonist.  Hence,  elec- 
trified bodies  attract  all  other  non-elec- 
trified bodies,  and  all  oppositely  electrified 
bodies,  in  order  to  saturate  themselves 
with  the  opposite  electricity  and  regain 
electrical  quiescence. 

7.  Attraction,  Electrodynamical.  A 
term  expressive  of  Ampere's  discovery, 
that  "  the  electricities  in  a  state  of  mo- 
tion, i.e.  as  electric  currents,  act  attrac- 
tively and  repulsively  on  each  other 
according  to  a  certain  law,"  in  a  manner 
resembling  the  polar  attraction  of  statical 
electricity,  i.  e.  of  electricity  in  a  state  of 
tension. 

8.  Attraction,  Magnetic.  The  property 
by  which  bodies  endowed  with  magnetism 
attract  certain  metals;  display  towards 
one  another  a  force  partly  attractive, 
partly  repulsive  ;  and  exhibit  a  tendency 
to  arrange  their  mass  in  a  certain  direc- 
tion. 

ATTWOOD'S  MACHINE.  A  ma- 
chine invented  by  Mr.  Attwood  for  cal- 
culating exactly  the  velocity  of  a  falling 
body  from  an  actual  measurement  of  its 
height,  and  the  time  which  it  takes  to 
reach  the  ground. 

AU'GITE  (avyii,  lustre).  Pyroxene. 
A  simple  mineral,  of  a  dark-green  or 
black  colour,  with  an  internal  shining 
lustre,  forming  a    constituent    part    of 


AUT 


AX1 


many  varieties  of  trap  and  volcanic 
rocks.  It  is  a  silicate  of  lime  and  mag- 
nesia. Augite  rock  is  a  particular  kind 
of  trap  rock,  consisting  of  augite  and 
compact  felspar,  the  former  being  pre- 
dominant or  in  equal  proportion. 

AURA  ELECTRICA.  A  gale  of  elec- 
tricity ;  a  term  expressive  of  electricity, 
as  received  from  a  point,  from  the  sensa- 
tion it  communicates. 

AURA'NTlA'CEiE.  The  Orange  tribe 
of  Dicotyledonous  plants,  abounding  in 
a  volatile,  fragrant,  bitter,  exciting  oil. 
Trees  or  shrubs  with  leaves  alternate, 
often  compound,  dotted  with  transparent 
receptacles  of  volatile  oil ;  flowers  poly- 
petalous  ;  stamens  hypogynous  ;  ovary 
many-celled ;  fruit  pulpy,  many-celled, 
its  rind  filled  with  receptacles  of  oil. 

AURE'LIA  {aurum,  gold).  Chrysalis. 
A  fanciful  name  for  the  nymph  or  pupa 
state  of  insect  life,  from  the  glittering 
spots  of  golden  hue  with  which  it  is 
sometimes  speckled. 

AU'RIC  ACID  (aurum,  gold).  Auric 
oxide.  A  name  proposed  by  Pelletier 
for  the  peroxide  of  gold,  from  its  property 
of  forming  salts  with  alkaline  bases. 

AURI'CULATED  (auricula,  a  little 
ear).  A  term  applied  to  a  few  bivalves 
which  have  a  flat  angulated  projection  on 
one  or  both  sides  of  the  umbones  or 
bosses.  These  processes  are  highly  de- 
veloped in  the  pecten,  and  are  merely 
an  incipient  modification  of  the  hinge 
margin  in  byssoarca  and  several  other 
genera.  The  term  is  also  applied,  in 
Botany,  to  leaves  which  have  two 
rounded  lobes  at  the  base. 

AU'RIFORM  (auris,  the  ear,  forma, 
likeness).  Ear-shaped  ;  as  applied  to  the 
haliotis  among  the  mollusca. 

AURFGA.  The  Charioteer ;  a  north- 
ern constellation,  consisting  of  sixty- 
six  stars,  the  principal  of  which  is  Ca- 
pella. 

AURO'RA  BOREA'LIS.  Northern 
Lights;  Polar  Lights,  or  Streamers.  A 
luminous  meteor,  generally  appearing  in 
the  northern  part  of  the  sky,  and  re- 
sembling the  Aurora,  or  morning  twi- 
light. It  is  usually  referred  to  the 
agency  of  electricity  in  the  upper  regions 
of  the  atmosphere. 

AUSTRAL.  The  six  signs  of  the  zo- 
diac, which  are  south  of  the  equinoctial, 
are  called  Austral  signs. 

AUTHORITY.  1.  This  term  is  em- 
ployed in  its  primary  sense,  when  we 
refer  to  any  one's  example,  testimony,  or 
judgment ;  in  this  sense  it  answers  pretty 
44 


nearly  to  the  Latin  auctoritas.  2.  Some- 
times it  is  employed  as  equivalent  to 
"potestas,"  power;  as  when  we  speak  of 
the  authority  of  a  magistrate. 

AUTO'MALITE.  Fahlunite.  A  mi- 
neral found  in  a  talcose  rock  at  Fahlun 
in  Sweden.  Its  constituent  parts  are 
alumina,  silica,  and  the  oxides  of  zinc 
and  of  iron. 

AUTOMATIC  MOTIONS  (aironaTOf, 
self-moving).  Those  muscular  actions 
which  are  not  dependent  on  the  mind, 
and  which  are  either  persistent,  or  take 
place  periodically  with  a  regular  rhythm, 
and  are  dependent  on  normal  causes 
seated  in  the  nerves  or  the  central  organs 
of  the  nervous  system. 

AUTUMN.  The  third  quarter  of  the 
year,  which  begins  when  the  sun  enters 
Libra,  that  is,  about  the  21st  or  22nd  of 
September,  when  the  days  and  nights 
are  equal. 

AUTUMNAL  EQUINOX.  The  time 
when  the  sun  enters  Libra,  or  the  de- 
scending point  of  the  ecliptic,  called  also 
the  Autumnal  point.  The  signs  Libra, 
Scorpio,  and  Sagittarius,  are  called  au- 
tumnal signs. 

A'VALANCHE.  A  mass  of  snow 
which,  being  detached  from  a  great  height 
in  the  Alps,  acquires  enormous  bulk 
by  accumulation  as  it  descends.  It  is 
termed,  in  the  dialects  of  Switzerland, 
lavange  and  lavanche. 

AVA'NTURINE.  A  variety  of  quartz 
containing  mica  spangles. 

A'VES  (avis,  a  bird).  The  fourth  class 
of  the  Vertebrata,  or  Encephalata,  com- 
prising birds;  a  class  of  oviparous  ani- 
mals, with  warm  blood,  a  double  circula- 
tion, a  covering  of  feathers,  and  arms 
constructed  for  flight. 

AVICU'LIDiE.  Mussels  and  Pearl 
Oysters ;  a  family  of  the  atrachian  bi- 
valves, named  from  the  genus  avicula ; 
the  animal  is  attached,  and  byssifer- 
ous ;  the  shells  are  lamellar,  internally 
perlaceous ;  the  valves  generally  gaping. 

AWN.  A  stiff  bristle,  formed  by  a 
continuation  of  the  midrib  of  a  bract  in 
certain  grasses,  and  commonly  called  the 
arista  or  beard. 

AXE-STONE.  A  sub-species  of  jade, 
used  by  the  New  Zealanders  for  making 
hatchets.  It  is  sometimes  called  Ama- 
zonian stone,  from  its  being  found  on  the 
banks  of  the  river  Amazon. 

AXI'LLA.  The  Latin  term  for  the 
arm-pit,  and  applied  to  other  parts  of  the 
animal  body  which  form  a  similar  angle. 
In  Botany,  it  denotes  the  angle  made  by 


A  X  I 


AZO 


a  leaf-stalk  with  the  stem,  the  normal 
position  of  the  hud,  which  is  hence  called 
axillary. 

A'XINITE  (af/i/n,  an  axe).  Thumer- 
stone.  A  mineral  found  at  Thum  in 
Saxony,  and  named  from  the  resemblance 
of  its  crystals  to  an  axe  in  the  form  and 
sharpness  of  their  edges. 

A'XIOM  {afimna,  dignity).  A  self- 
evident  proposition,  incapable  of  being 
established  by  proof,  and  assumed  as  the 
basis  of  demonstration. 

A'XIS  (af  coy,  the  axle-tree  of  a  chariot). 
A  term  applied  to  an  imaginary  straight 
line  passing  through  the  centre  of  a  body, 
and  on  which  the  body  turns.  The  axis 
of  the  earth  is  a  line  of  this  kind  passing 
from  one  pole  to  the  other;  and,  if  we 
suppose  this  line  to  be  extended  in  both 
directions,  it  will  become  an  axis  of  the 
heavens,  and  will  mark  two  points  which 
are  also  called  poles,  around  which,  or 
rather  their  line  of  junction,  all  the  fixed 
stars  appear  to  revolve. 

1.  Axis,  rotation  on.  The  different 
points  of  a  body  may  at  the  same  time 
move  in  different  directions ;  this  is 
called  a  rotatory  motion.  Rotation  on  an 
axis  implies,  in  addition  to  this  rotatory 
motion,  that  all  the  parts  of  the  body 
shall  revolve  around  an  imaginary  right 
line  in  a  state  of  rest,  called  the  axis. 

2.  Axis,  free  or  moveable.  A  term 
applied  to  an  axis  which  is  free  from  all 
pressure,  in  consequence  of  the  mass  of 
the  body  surrounding  it  being  so  equally 
arranged  about  it,  that  the  centrifugal 
forces  of  its  particles  mutually  counteract 
one  another.  The  axis  of  the  earth  is  a 
free  or  moveable  axis. 

3.  Axis  of  refraction.  The  right  line 
drawn  perpendicular  to  the  surface  of  the 
refracting  medium  through  the  point  of 
incidence  of  the  refracted  ray.  Of  crys- 
tals which  possess  the  property  of  double 
refraction,  many,  like  Iceland  spar,  have 
only  one  axis  of  double  refraction ;  others 
have  two  axes,  which  are  variously  in- 
clined to  each  other,  as  the  topaz.  When 
the  ray  of  extraordinary  refraction  is  in- 
clined from  the  axis,  the  crystal  is  said 
to  have  a,  negative  axis;  when  it  is  in- 
clined towards  it,  more  than  the  ordinary 
ray,  the  crystal  is  said  to  have  a  positive 
axis. 

4.  Axes  of  crystals.  The  lines  which 
join  the  points,  and  pass  through  the 
middle  of  a  crystal,  are  called  its  axes. 
Most  of  these  bodies  have  three  such 
axes  at  right  angles  to  each  other:  that 
which  is  most  unlike  the  other  two,  is 

45 


called  the  principal  axis,  and  the  other 
two  secondary  or  subordinate  axes. 

5.  Axis  of  a  lens.  A  right  line  drawn 
through  the  optical  centre  of  the  lens, 
and  perpendicular  to  both  its  surfaces. 
At  this  point  no  refraction  is  produced 
on  perpendicular  rays. 

6.  Axis  of  a  spherical  mirror.  A  right 
line  which  passes  through  the  geometri- 
cal and  the  optical  centres  of  the  mirror. 

7.  Axis  of  a  cone.  A  right  line  drawn 
from  the  vertex  of  the  cone  to  the  centre 
of  its  circular  base. 

8.  Axes  of  an  ellipse.  These  are  called 
the  major  and  the  minor  axes,  and  they 
are  respectively  synonymous  with  the 
transverse  and  the  conjugate  diameters. 

9.  Axis  of  a  parabola.  The  line  which, 
passing  through  the  vertex  of  the  para- 
bola, divides  the  figure  into  two  equal 
and  similar  portions. 

10.  Axis  of  a  magnet.  The  imaginary 
line  which  connects  the  north  and  south 
poles  of  a  magnet. 

11.  Axis  anticlinal.  The  imaginary 
line  lying  between  the  strata  which  dip 
in  opposite  directions  on  the  two  sides  of 
a  hill  or  of  a  valley.  In  a  row  of  houses 
with  steep  roofs  facing  the  south,  the 
slates  represent  inclined  strata  dipping 
north  and  south,  and  the  ridge  is  an  east 
and  west  anticlinal  axis. 

A'YMESTRY  LIMESTONE.  A  group 
of  the  Ludlow  rocks,  consisting  of  grey 
or  bluish  argillaceous  limestone,  full  of 
the  remains  of  shells  and  corals. 

A'ZIMUTH.  An  Arabic  term  de- 
noting the  angular  distance  of  a  celes- 
tial object  from  the  north  or  south  point 
of  the  horizon,  when  the  object  is  re- 
ferred to  the  horizon  by  a  vertical  circle. 
Or,  it  is  the  angle  comprised  between 
two  vertical  planes,  one  passing  through 
the  elevated  pole,  the  other  through  the 
object. 

1.  Azimuth  circles.  Great  circles  of 
the  sphere,  passing  through  the  zenith, 
and  intersecting  the  horizon  at  right 
angles. 

2.  Azimnih  compass.  A  compass  used 
at  sea  for  finding  the  horizontal  distance 
of  the  sun  or  a  star  from  the  magnetic 
meridian. 

3.  Azimuth  dial.  A  dial  of  which  the 
style  or  gnomon  is  perpendicular  to  the 
plane  of  the  horizon,  and  so  called  from 
its  shadow  marking  the  sun's  azimuth. 

A'ZOTANE.  Chloride  of  azote.  The 
term  is  derived  from  Davy,  who  pro- 
posed to  designate  the  compounds  of 
chlorine  by  the  termination  ane. 


B  A  C 


BAL 


A'ZOTE  (a  pnv.,  £w\h  life).  A  gas 
constituting  73  per  cent,  of  the  atmo- 
sphere, and  thus  named  from  its  being 
incapable  of  supporting  respiration.  It 
is  more  commonly  called  nitrogen,  from 
its  being  the  basis  of  nitric  acid. 

AZOTIC  and  AZO'TOUS  ACIDS. 
Names  given  by  Thenard  to  the  nitric 
and  the  nitrous  acids,  respectively,  of 
other  chemists.  The  latter  acid  was 
termed  hyponitrous  by  Turner. 


A'ZURE.  A  fine  blue  pigment,  com- 
monly called  smalt,  consisting  of  a  glass 
coloured  with  oxide  of  cobalt,  and  ground 
to  an  impalpable  powder. 

AZURE  STONE.  Lapis  lazuli.  An 
azure  blue  mineral,  from  which  ultra- 
marine is  prepared. 

A'ZURITE.  Prismatic  azure  spar,  or 
Lazulite.  A  mineral  occurring  in  mica 
slate,  and  consisting  of  alumina,  silica, 
magnesia,  lime,  and  oxide  of  iron. 


B 


B.  in  astronomical  tables,  stands  for 
Bissextile,  or  Leap  year. 

BA'BINGTONITE.  A  crystalline  min- 
eral, associated  with  cleavlandite,  flesh- 
coloured  felspar,  and  green  amphibole. 

BA'CCA.  A  berry  ;  an  inferior,  inde- 
hiscent,  pulpy  fruit,  as  the  gooseberry. 
The  seeds  lose  their  adhesion  when  ripe, 
and  lie  loose  in  the  pulp.  The  term  is, 
however,  differently  employed  by  some 
botanical  writers.  Link  applies  the  term 
bac^a  sicca  to  a  fruit  which  is  fleshy  when 
unripe,  dry  when  ripe,  and  then  distin- 
guishable from  the  capsule  by  not  being 
brown. 

BA'CC  ATE  (bacca,  a  berry).  Berried ; 
having  a  juicy  succulent  texture,  as  the 
calyx  of  blitum. 

BACK  STAFF.  An  instrument  in- 
vented by  Capt.  J  Davis  for  taking  the 
sun's  altitude  at  sea.  In  using  it  the 
observer  was  obliged  to  turn  his  back  to 
the  sun.  It  is  now  superseded  by  the 
quadrant  and  the  sextant. 

BACONIAN  PHILOSOPHY.  A  sys- 
tem of  philosophy  founded  on  induction, 
enforced  by  the  talent  and  writings  of 
Francis  Bacon,  Lord  Verulam.  This  sys- 
tem holds  an  intermediate  place  between 
the  merely  empirical  and  the  dogmatical 
schools.  "  While  the  one,"  he  observes, 
"like  ants,  content  themselves  with 
heaping  up  materials  for  immediate  use, 
the  latter,  after  the  manner  of  spiders, 
spin  webs  out  of  their  own  brain.  There 
is  a  better  and  a  middle  way— that  of  the 
bee,  which  derives,  indeed,  its  material 
from  the  flowers  of  the  garden  and  the 
field,  but  converts  and  digests  it  by  its 
own  proper  virtue." 

BA'CUUTE  (baculus,  a  staff).  An 
extinct  genus  of  Molluscous  animals, 
4G 


allied  to  the  Nautilus,  which  inhabit  a 
str  light-chambered  shell  resembling  a 
staff. 

BAFKALITE.  A  light-green  variety 
of  augite,  found  at  the  mouth  of  a  river 
which  flows  into  lake  Baikal  In  Siberia. 

BA'LA  LIMESTONE.  A  dark-coloured 
slaty  limestone,  forming  a  subordinate 
portion  of  the  Cambrian  group  of  rocks. 
In  Westmoreland  it  is  100  feet  in  thick- 
ness, and  both  there  and  in  Wales  con- 
tains organic  remains. 

BALiE'NID^E  (<pd\aiva,  bal&na,-  a 
whale).  The  Whale  tribe  of  cetaceous 
Vertebrata,  in  which  the  head  constitutes 
one-third,  or  even  one- half,  of  the  entire 
length.  By  this  disproportionate  size 
they  are  distinguished  from  the  Delphi- 
nidcB,  or  Dolphin  tribe.  By  the  term 
balcenopUra  (irrepov,  a  fin),  De  Lacepede 
distinguished  from  the  other  balaenas 
those  whales  which  have  an  adipose  fin 
on  their  back,  and  are  hence  called  fin- 
ners  by  sailors. 

BALANCE  (bilanx,  from  bis  and  lanx, 
i.  e.  a  duabus  lancibus,  a  beam  with 
balances).  One  of  the  simple  mechani- 
cal powers,  consisting  of  a  lever  turning 
on  a  pivot  or  fulcrum,  and  constructed 
for  the  purpose  of  finding  the  weight  of 
different  bodies.  The  lever,  or  rod,  of  a 
balance  is  termed  the  beam,  and  the  parts 
of  the  beam  on  each  side  of  the  pivot  on 
which  it  turns  are  its  arms.  In  the  com- 
mon balance  those  arms  are  equal,  and 
balance  each  other;  and  its  ends,  to 
which  the  body  to  be  weighed  and  its 
equivalent  counterpoise  are  hung,  are 
called  the  points  of  suspension. 

1.  Roman  Balance,  or  Steel-yard.  This 
kind  of  lever  differs  from  the  common 
balance,  in  having  its  support  near  one 


B  A  L 


BAR 


end,  instead  of  in  the  middle  ;  and  also, 
in  having  the  weights  suspended  hy 
hooks  instead  of  being  placed  in  a  dish. 
Here  the  fulcrum  is  between  the  power 
and  the  weight.  This  is  the  principle 
also  of  the  Chinese  balance. 

2.  Danish  Balance.  This  kind  of  lever 
consists  of  a  bar  of  wood  or  iron,  having 
a  leaden  weight  at  one  extremity,  and 
the  goods  to  be  weighed  fixed  in  a  hook 
at  the  other.  The  bar  is  suspended  by 
a  loop,  which  is  moved  backward  and 
forward  until  the  equilibrium  is  obtained. 
The  weight  of  the  goods  and  the  leaden 
weight  are  then  to  each  other  recipro- 
cally as  their  respective  distances  from 
the  loop. 

BALANCE  ELECTROMETER.  An 
instrument  constructed  on  the  applica- 
tion of  the  common  balance  and  weights, 
for  the  purpose  of  estimating  the  mutual 
attraction  of  oppositely  electrified  sur- 
faces. 

BALANCE  OF  TORSION.  A  deli- 
cate electrometer,  invented  by  Coulomb, 
on  the  principle  of  establishing  an  equi- 
librium between  the  force  of  electricity 
and  that  of  the  torsion,  or  twisting, 
of  a  fibre  of  the  web  of  the  silk-worm. 

BA'LANCERS.  A  term  generally  ap- 
plied to  the  posterior  pair  of  wings  in 
Dipterous  insects,  in  which  they  appear 
in  the  condition  of  minute  clavate  ap- 
pendages. 

BALANI'DA  ( balanus,  an  acorn). 
Acorn-barnacles ;  an  order  of  Cirrhopods, 
named  from  the  genus  balanus,  and  cha- 
racterized by  their  being  enclosed  in  a 
conical  shell,  adherent  by  its  base  to 
foreign  substances,  and  closed  at  its  apex 
by  four  valves. 

BA'LANOPHO'RE^E.  A  small  fa- 
mily of  leafless  rhizanths,  parasitical 
upon  roots,  named  from  the  genus  bala- 
nophora,  and  natives  of  the  West  Indies, 
South  America,  &c.  Their  properties 
are  unknown. 

BA'LAS  RUBY.  A  technical  term 
for  the  bright  red  varieties  of  the  spinel, 
a  sub-species  of  ruby. 

BALAU'STA  {(3a\av(niov,  the  flower 
of  the  wild  pomegranate).  A  term  ap- 
plied, in  Botany,  to  the  many-celled, 
many-seeded,  inferior,  indehiscent  fruit 
of  the  pomegranate. 

BALDWIN'S  PHOSPHORUS.  The 
ignited  nitrate  of  lime.  This  salt  de- 
rives its  name  from  its  property  of  emit- 
ting a  beautiful  white  light  in  the  dark, 
when  kept  in  a  stoppered  phial,  and  ex- 
posed for  some  time  to  the  rays  of  the  sun. 
47 


BALLISTIC  PENDULUM  (/3d\X«>, 
to  throw).  A  heavy  wooden  pendulum, 
for  measuring  the  velocity  of  cannon  and 
musket  balls,  and  for  determining  the 
resistance  of  the  air  to  rapid  motions. 
The  mechanical  problem  to  be  solved  is 
this  : — Given,  the  weight  of  the  shot,  the 
place  at  which  it  strikes,  the  weight, 
form,  &c,  of  the  pendulum,  and  the 
number  of  vibrations  produced  upon  it 
by  the  shot ;  required,  the  velocity  of  the 
shot. 

BALLOON  {ballon,  French,  a  little 
ball).  A  chemical  instrument  or  re- 
ceiver, of  a  spherical  form,  for  condens- 
ing vapours  from  retorts.  The  term 
balloon  signifies  any  spherical  hollow 
body,  of  whatever  material  composed,  or 
to  whatever  purpose  applied  :  in  its  most 
common  use,  it  denotes  a  machine  for 
navigating  the  air. 

BA'LSAMS.  Vegetable  juices,  either 
liquid,  or  becoming  spontaneously  con- 
crete, and  consisting  of  ethereal  or 
essential  oils  with  resin  and  benzoic  acid. 
The  liquid  balsams  are  copaiva,  opo- 
balsam,  balsam  of  Peru,  storax,  and 
Tolu ;  the  concrete  are  benzoin,  dragon's 
blood,  and  red  or  concrete  storax.  Those 
compounds  which  have  no  benzoic  acid 
are  miscalled  balsams,  being,  in  fact,  true 
turpentines. 

BALSAMA'CEiE.  Balsamiflute.  An 
order  of  Dicotyledonous  plants,  found  ia 
tropical  India,  and  characterized  by  their 
balsamic  products.  The  fragrant  resin 
storax  is  yielded  by  several  species  of 
Liquidambar,  the  only  genus  of  the 
order. 

BALSAM  I  NA'CE^E.  The  Balsam 
tribe  of  Dicotyledonous  plants  ;  a  small 
order  of  plants,  closely  allied  to  the 
Geraniacece,  and  chiefly  remarkable  for 
the  elastic  force  with  which  the  valves  of 
the  fruit  separate  when  ripe,  and  expel 
the  seeds. 

BANDA'NA.  A  mode  of  calico  print- 
ing practised  in  India,  by  which  white  or 
brightly  coloured  spots  are  produced  upon 
a  red  or  dark  ground. 

BARBA'DOS  TAR.  Petroleum.  A 
species  of  bitumen,  differing  from  naphtha 
in  its  greater  weight  and  impurity. 

BARDIGLIO'NE.  A  blue  variety  of 
anhydrite,  cut  and  polished  for  orna- 
mental purposes. 

BARPLLA.  The  commercial  name  of 
the  impure  carbonate  of  soda  extracted 
from  the  ashes  of  the  plants  salsola  and 
salicornia,  and  imported  from  Spain  or 
the  Levant.     Kelp,  or  British  barilla,  is 


BAR 


BAR 


a  more  impure  alkali,  made  in  this  coun- 
try by  burning  various  sea-weeds. 

BA'RIUM  (/3api)i,  heavy).  A  peculiar 
metal,  the  basis  of  the  alkaline  oxide  or 
earth  barytes,  named  from  the  great 
density  of  its  compounds. 

BARK  OF  PLANTS.  The  external 
envelope  of  trees  and  shrubs.  It  was 
formerly  distinguisbed  into  an  external 
cortical  or  cellular  integument,  and  an 
internal  or  fibrous  portion,  called  liber. 
More  recently,  bark  has  been  distin- 
guished into  four  portions : — 

1.  Epidermis.  The  external  and  cel- 
lular envelope,  continuous  with  the  epi- 
dermis of  the  leaves.  Tbis  is  never 
renewed;  the  following  parts  increase 
by  successive  additions  to  their  in- 
terior. 

2.  Epi-phlceum  {kni,  upon,  <p\oio?, 
bark).  A  cellular  portion  lying  imme- 
diately under  the  epidermis.  Cork  is  the 
epiphlceum  of  the  Quercus  suber. 

3.  Meso-phloeum  (jueo-of,  middle,  <p\oios, 
bark).  A  cellular  portion,  lying  imme- 
diately under  the  epiphlceum.  This  por- 
t:on  differs  from  the  preceding  in  the 
direction  of  its  cells. 

4.  Endo-phlceum  {evdov,  within,  <p\otos, 
bark).  The  liber,  part  of  which  is  cellu- 
lar, part  woody. 

BA'ROLITE  (papvs,  heavy,  \t'0o?,  a 
stone).  Heavy  stone  ;  a  carbonate  of 
baryta. 

BARO'METER  (/Japop,  weight,  /ue- 
Tpov,  a  measure).  An  instrument  for 
measuring  the  weight  or  pressure  of  the 
atmosphere,  by  balancing  a  column  of  air 
against  a  column  of  mercury ;  and,  by 
that  test,  measuring  heights  and  depths, 
determining  variations  in  the  state  of  the 
air,  and  foretelling  changes  in  the  wea- 
ther. "When  employed  for  determining 
the  degree  of  rarefaction  attained  in 
the  receiver  of  an  air-pump,  it  is  called 
a  barometer-gauge. 

1.  The  cistern  barometer  is  a  Torricel- 
lian tube,  whose  open  end  is  immersed 
in  a  wider  cistern  of  mercury.  The  zero 
point  is  on  a  level  with  the  surface  of  the 
mercury.  This  is  the  oldest  form  of  the 
instrument. 

2.  The  common  barometer  is  a  Torri- 
cellian tube,  whose  open  end  is  turned 
up  and  is  of  a  spherical  form.  The 
globe  performs  the  office  of  the  cistern 
described  in  the  preceding  barometer : 
the  scale  is  graduated  from  the  same 
point  in  both  these  instruments. 

3.  De  Luc's  syphon  barometer  consists 
of  a  glass  tube  bent  upwards  so  as  to 

48 


form  two  parallel  legs  :  the  longer  is  her- 
metically sealed,  and  constitutes  the 
Torricellian  tube  ;  the  shorter  is  open, 
and  on  the  surface  of  the  mercury  the 
pressure  of  the  atmosphere  is  exerted. 
The  difference  between  the  levels  in  the 
two  legs  is  the  barometric  height. 

BA'ROMETZ  {baronez,  Russian,  a 
little  lamb).  A  species  of  Aspidium,  or 
shield  fern,  which,  from  its  procumbent 
position  and  shaggy  appearance,  has  ac- 
quired the  name  of  'Scythian  lamb," 
and  the  credit  of  possessing  some  of  the 
properties  of  this  animal. 

BA'ROSCOPE  (/Sapor,  weight,  o-kottco), 
to  perceive).  A  perceiver  of  weight ;  a 
term  sometimes  applied  to  the  barometer. 
Etymologically  speaking,  a  baroscope  is 
not  a  barometer,  thotigh  a  barometer  is  a 
baroscope. 

BA'RRAS,  or  GALIPOT.  The  resin- 
ous incrustation  on  the  wounds  made  in 
fir-trees. 

BA'RRIER  REEF.  A  coral  produc- 
tion, similar  to  the  Atoll,  or  coral  island. 
It  runs  parallel  with  the  shores  of  a 
larger  island  or  continent,  separated, 
however,  from  the  land  by  a  broad  and 
deep  lagoon  channel,  and  having  the 
outer  side  as  steep  as  in  the  lagoon 
islands. 

BA'RTER.  A  rule  in  Arithmetic,  by 
which  the  values  of  commodities  of  dif- 
ferent kinds  are  compared,  for  the  pur- 
pose of  exchange. 

BARYSTRO'NTIANITE.  Stromnite. 
A  mineral  found  in  veins,  or  rather 
nests,  accompanied  by  galena,  at  Strom- 
ness,  in  Orkney.  It  consists  of  the  car- 
bonates of  strontia  and  of  lime,  sulphate 
of  baryta,  and  oxide  of  iron. 

BARY'TES  (/3aPw,  heavy).  Baryta. 
The  protoxide  of  barium,  an  alkaline 
earth,  the  heaviest  of  all  the  earths,  and 
a  violent  poison.  The  native  sulphate  is 
called  heavy  spar,  or  cawk.  The  native 
carbonate  has  been  named,  after  Dr. 
Withering,  its  discoverer,  wilherite.  A 
solution  of  barytes  in  water  is  called 
barytes  water,  and  is  used  as  a  chemical 
re-agent. 

BARY'TIN.  A  new  vegetable  base, 
discovered  in  the  rhizome  of  Veratrum 
album,  and  named  in  consequence  of  its 
being  precipitated  from  its  solution,  like 
baryta.     See  Jervin. 

BARY'TO-CALCITE.  A  mineral 
found  in  Cumberland,  consisting  of  the 
carbonates  of  baryta  and  of  lime,  with 
an  outer  coating  of  sulphate  of  baryta. 

BA'RYTON     (/3aPv?,    heavy,    tovov, 


B  AS 


B  AS 


tone).  Baritone.  That  compass  of  the 
male  voice  which  is  between  those  of  the 
tenor  and  of  the  base.  The  term  bari- 
tenor,  employed  by  Bennati,  is  preferable, 
as  it  expresses  what  is  really  meant,  viz. 
a  high  base. 

BA'RYTONE  VERBS  (/3aPv?,  heavy, 
T01/09,  tone).  That  class  of  Greek  verbs 
which  terminate  in  a>,  and  have  either  a 
consonant  before  «,  or  a  vowel  a,  e,  o, 
before  a>.  These  are  called  barytone, 
because  they  have  the  accent  (acute)  on 
the  penultima,  and  the  last  syllable  neces- 
sarily has  the  grave  accent,  not  expressed 
in  writing. 

BA'SALT  (basal,  iron,  Ethiopian).  One 
of  the  most  common  varieties  of  the 
Trap-rocks.  It  is  a  dark  green  or  black 
stone,  composed  of  augite  and  felspar, 
very  compact  in  texture,  and  of  con- 
siderable hardness,  often  found  in  regular 
pillars  of  three  or  more  sides,  called 
basaltic  columns.  These  occur  in  the 
Giants'  Causeway,  and  at  Fingal's  Cave 
in  StafFa.  The  rock  often  contains 
much  iron.  Basaltic  hornblende  oc- 
curs in  various  basaltic  and  floetz  trap- 
rocks. 

BA'SANITE  (paaavifa,  to  test,  from 
pdaavos,  a  Lydian  stone).  A  stone  by 
which  the  purity  of  gold  was  formerly 
tested;  it  consists  of  silica,  lime,  mag- 
nesia, carbon,  and  iron. 

BASE  or  BASIS  (/3«<r<?,  a  base).  A 
chemical  term  applied  to  alkalies,  earths, 
and  metallic  oxides,  in  their  relations  to 
the  acids  and  salts.  It  is  sometimes  also 
applied  to  the  particular  constituents  of 
an  acid  or  oxide,  on  the  supposition  that 
the  substance  combined  with  the  oxygen, 
&c.  is  the  basis  of  the  compound  to 
which  it  owes  its  particular  qualities. 
This  notion  seems  unphilosophical,  as 
these  qualities  depend  as  much  on  the 
state  of  combination  as  on  the  nature  of 
the  constituent. —  Ure. 

1.  In  the  Arts,  the  term  base  is  syno- 
nymous with  mordaunt,  and  is  applied  to 
a  substance  used  in  dyeing,  which  has  an 
affinity  for  both  the  cloth  and  the  colour- 
ing matter. 

2.  In  Malacology,  the  term  base  is 
generally  used  in  opposition  to  the  apex, 
or  pointed  extremity  of  univalve  shells. 
In  bivalves  which  adhere  to  other  sub- 
stances by  one  of  their  valves,  as  in 
spondylus,  that  which  adheres  is  termed 
the  basal  valve  ;  in  unattached  bivalves, 
the  term  is  not  correctly  admissible.  In 
spiral  shells,  the  last  or  largest  whorl  is 
termed  the  basal  whorl. 

49 


3.  In  Geometry,  the  base  is  the  lowest 
side  of  the  perimeter  of  any  figure.  The 
base  of  a  triangle  is,  properly,  the  side 
which  is  parallel  to  the  horizon,  though 
the  term  may  be  applied  to  either  of  the 
other  sides.  In  rectangled  triangles,  the 
base  is,  properly,  the  side  opposite  to  the 
right  angle. 

BASE  VOICE.  The  lowest  compass 
of  the  human  voice,  usually  ranging 
from  G  or  F  below  the  base  staff  to  D  or 
E  above  it. 

BASIC  WATER.  A  term  applied  in 
cases  in  which  water  appears  to  act  the 
part  of  a  base:  phosphoric  acid,  for  in- 
stance, ceases  to  be  phosphoric  acid,  un- 
less three  equivalents  of  water  to  one  of 
acid  be  present. 

BASI'DI A.  Small  bases ;  a  term  ap- 
plied to  the  cells  on  the  apex  of  which 
the  spores  of  fungaceous  plants  are 
formed. 

BASIGY'NIUM  (/2aW,  a  base,  -yw^ 
a  female).  Podogynium.  A  botanical 
term  applied  to  the  long  stalk  upon 
which  the  ovary,  instead  of  being  sessile, 
is  seated  in  certain  plants,  as  in  the  Pas- 
sion flower.  It  is  frequently  called  the 
thecaphore  and  gynophore. 

BA'SILAR  (basis,  a  base).  Belonging 
to  the  base ;  in  Zoology,  to  that  of  the 
skull. 

BA'SIN  (bassin,  French).  A  term  ap- 
plied, in  Physical  Geography,  to  the  whole 
extent  of  country  from  which  the  waters 
of  a  particular  river  are  drawn.  In  Geo- 
logy, the  term  denotes  those  depressions 
of  the  surface  of  the  earth  in  which 
waters  accumulate  so  as  to  form  lakes : 
of  this  kind  are  the  lakes  of  North  Ame- 
rica, lake  Aral,  the  Caspian  and  Dead 
Seas,  &c. 

Basins  of  Paris,  of  London.  Deposits 
lying  in  a  hollow  or  trough,  formed  of 
older  rocks.  The  term  basin  is  some- 
times used,  in  Geology,  almost  synony- 
mously with  "formation,"  to  express  the 
deposits  lying  in  a  certain  cavity  or  de- 
pression in  older  rocks. 

BA'SSORINE.  A  substance  extracted 
from  the  gum  resins  which  contain  it,  by 
treating  them  successively  with  water, 
alcohol,  and  ether.  Its  name  is  derived 
from  bassora,  the  gum  in  which  it  was 
first  discovered. 

BA'SYLE  (/?aW,  a  base,  v\t),  nature 
or  principle).  A  term  proposed  by  Mr. 
Graham  to  denote  the  metallic  radical  of 
a  salt.  Thus,  sodium  is  the  basyle  of 
sulphate  of  soda;  soda  is  the  base,  and 
sulphatoxygen  the  salt  radical,  if  the 
D 


BAY 


BEL 


salt  be  viewed  as  consisting  of  sulphat-  I 
oxide  of  sodium. 

BATH,  CHEMICAL.  An  apparatus 
for  modifying  and  regulating  the  heat  in 
various  chemical  processes,  by  inter- 
posing sand  or  some  other  substance 
between  the  fire  and  the  vessel  intended 
to  be  heated.  The  water  bath,  formerly 
called  balneum  mar ias,  and  the  sand  bath, 
are  most  commonly  used.  Solution  baths, 
consisting  of  saturated  solutions,  will 
produce  temperatures  as  high  as  360°. 
For  higher  temperatures,  metal  baths  are 
employed,  as  of  mercury,  fusible  metal, 
&c. ;  the  temperature  may  thus  be  raised 
to  600°. 

BATH,  ELECTRICAL.  This  is  ad- 
ministered by  placing  a  person  on  an 
insulating  stool,  and  directing  the  elec- 
tric current  from  the  conductor  to  dif- 
ferent parts  of  the  body  by  means  of  some 
pointed  conductor. 

BATRA'CHIA  (/Sarpaxor,  a  frog).  An 
order  of  the  class  Reptilia,  comprising 
the  frog,  toad,  salamander,  and  siren. 

BATTERY,  ELECTRICAL.  An  ar- 
rangement of  Leyden  jars  which  commu- 
nicate together  by  both  their  inner  and 
outer  surfaces,  and  are  thus  rendered 
capable  of  being  charged  with  electricity 
and  discharged  at  the  same  time. 

1.  Battery,  Galvanic.  A  combination 
of  several  pairs  of  zinc  and  copper  plates 
soldered  together,  and  so  arranged  that 
the  same  metal  shall  always  be  on  the 
same  side  of  the  compound  plate.  A 
combination  of  this  kind  is  sometimes 
termed  a  compound  hydro-electric  battery, 
or  a  voltaic  pile  or  battery. 

2.  Battery,  Trough.  In  this  apparatus 
the  zinc  and  copper  plates  are  fastened 
to  a  slip  of  mahogany  wood,  and  united  in 
pairs  by  a  piece  of  metal  soldered  to  each. 
The  whole  are  then  placed  in  a  trough 
of  wood,  or  of  Wedgewood's  ware,  divided 
into  cells,  so  that  each  pair  of  plates 
shall  enclose  a  partition  of  the  trough, 
each  cell  of  the  trough  containing  a  plate 
of  zinc  connected  with  the  copper  plate 
of  the  succeeding  cell,  and  a  plate  of 
copper  joined  with  the  zinc  plate  of  the 
preceding  cell. 

3.  Constant  Battery.  A  term  applied  to 
a  battery  in  which  the  effect  of  the  cur- 
rent is  for  a  long  time  unimpaired,  owing 
to  the  employment  of  concentrated  nitric 
acid,  by  means  of  which  the  platinum, 
and  by  analogy  the  carbon  also,  become 
depolarized  and  relatively  exalted  in  their 
electromotive  functions.  Of  this  kind 
are  the  batteries  of  Grove  and  Bunsen. 

50 


BAY.  A  projection  of  the  ocean  into 
the  continent,  of  less  expanse  than  that 
of  a  sea,  but  communicating  with  the 
ocean  by  a  broader  passage.     See  Gulf. 

BAY  SALT.  A  general  name  for 
coarse-grained  salt,  but  particularly  ap- 
plied to  salt  obtained  by  spontaneous 
evaporation  of  sea-water  in  large  shallow 
pits  or  bays. 

BDE'LLIUM.  A  name  applied  to  two 
gum-resinous  substances.  One  of  these 
is  the  Indian  bdellium,  or  false  myrrh, 
procured  from  the  Amyris  commiphora. 
The  other  is  called  African  bdellium, 
and  is  obtained  from  the  Heudolotia 
African  a. 

BEAD-PROOF.  A  term  denoting  the 
strength  of  spirituous  liquors,  as  shown 
by  the  continuance  of  the  bubbles  or 
beads  on  the  surface. 

BEARING.  A  term  denoting,  in 
Navigation,  the  situation  of  one  place 
from  another  with  respect  to  the  points 
of  the  compass.  Thus,  if  A  lies  in  the 
direction  of  south-west  from  B,  then  to 
an  observer  at  B,  A  is  said  to  bear  south- 
west, or  to  have  a  south-west  bearing; 
while  to  an  observer  at  A,  the  point  B 
will  bear  north-east,  or  have  a  north-east 
bearing.  To  take  bearings,  is  to  ascer- 
tain the  points  of  the  compass  on  which 
objects  lie. 

BEATS.  A  term  applied,  in  Music, 
to  the  beatings  or  pulsations  resulting 
from  the  joint  vibrations  of  two  sounds 
of  the  same  strength  and  nearly  the  same 
pitch ;  that  is,  of  two  sounds  differing 
little,  if  at  all,  in  intensity,  and  almost, 
but  not  exactly,  in  unison :  when  the 
unison  is  complete,  no  beats  are  heard. 

BEGUIN'S  SULPHURATED  SPI- 
RIT. A  variety  of  hydrosulphate  of 
ammonia,  commonly  called  hepatized 
ammonia. 

BE'LEMNITE  (/3e\e/ivov,  a  dart).  An 
extinct  genus  of  the  Cephalopods,  allied 
to  the  sepia,  and  having  a  long,  straight, 
and  chambered  conical  shell,  resembling 
a  dart,  in  the  interior  of  the  body.  They 
have  been  termed  lapides  lyncis,  from 
an  old  idea  that  they  came  from  the  lynx ; 
and,  from  their  resemblance  to  fingers, 
petrified  fingers,  devil's  fingers,  spectre 
candles,  &c. 

BELLA'TRIX.  A  star  of  the  second 
magnitude,  the  smaller  of  the  two  bright 
upper  stars  in  Orion.  It  is  marked  y  by 
Bayer,  and  24  by  Flamstead. 

BELL-METAL.  An  alloy  of  100  parts 
of  copper  with  20  to  25  of  tin. 

BELL-METAL  ORE.    A  designation 


BET 


BI 


of  the  sulphuret  of  tin  found  in  Corn- 
wall, from  the  appearance  of  bronze  or 
bell-metal  which  it  possesses,  in  conse- 
quence of  its  containing  copper  pyrites. 

BENGALEE  YEAR.  This  appears 
to  have  been  once  identical  with  the 
Hegira;  but  the  solar  computation  having 
subsequently  been  adopted,  of  which  the 
years  exceed  those  of  the  Hegira  by  11 
days,  it  has  lost  nearly  11  days  every 
year,  and  is  now  about  9  years  later,  the 
year  1245  of  the  Hegira  having  com- 
menced in  July,  1829,  and  the  Bengalee 
year  1236  having  begun  13th  April  of  the 
same  year.  The  number  593  must  be 
added  to  bring  this  to  the  Christian  era. 

BENZOIC  ACID.  Flowers  of  Ben- 
jamin. An  acid  exhaled  from  benzoin, 
dragon's  blood,  and  other  resins,  by 
heat. 

BENZO'IN.  Asa  dulcis.  A  balsam 
which  exudes  from  incisions  made  in  the 
Styrax  Benzoin,  or  Benjamin-tree. 

BE'NZOYL.  Benzoile  or  benzule  of 
several  English  chemical  writers.  The 
hypothetical  radical  of  a  series  of  com- 
pounds, including  benzoic  acid,  from 
which  it  derives  its  name,  and  the 
essence  or  volatile  oil  of  bitter  almonds. 

BE'RBERIN.  A  crystalline  substance 
of  a  fine  yellow  colour,  derived  from  the 
bark  of  the  barberry  root ;  used  as  a  dye 
stuff. 

BERG,  or  ICE  BERG  (berg,  Swedish, 
mountain).  A  mountain  of  ice,  met  with 
in  the  Polar  Seas.  Flat  sheets  of  wide- 
spread ice  are  called  fields ;  and  small 
portions,  floes,  from  their  being  found 
floating. 

BE'RGMEHL.  Literally,  Mountain 
meal;  an  earth,  so  named  in  Sweden, 
resembling  fine  flour,  and  celebrated  for 
its  nutritious  qualities.  It  is  found  to 
be  composed  entirely  of  the  shells  of 
loricated  animalcules,  which  having  accu- 
mulated at  the  bottom  of  the  waters  in 
which  the  living  animals  are  found,  form 
a  stratum  of  considerable  thickness. 

BE'RYL.  A  variety  of  the  emerald;  a 
mineral  or  gem,  usually  of  a  green  colour 
of  various  shades,  passing  into  honey- 
yellow  and  sky-blue.  When  coloured 
green  by  oxide  of  chromium,  it  forms 
the  true  emerald,  and  when  colourless 
and  transparent,  aqua  marina. 

Chryso-b&ryl  (xpuao?,  gold).  One  of  the 
finest  of  the  gems,  consisting  of  glucina 
and  alumina. 

BE'TELGEUSE.    A  star  of  the  first 
magnitude  in  the  southern  constellation 
Orion. 
51 


BE'ZOAR  (pdd-zahr,  Persian,  a  de- 
stroyer of  poison).  A  morbid  concretion 
formed  in  the  bodies  of  land  animals. 
Such  are  the  hog-bezoar,  found  in  the 
stomach  of  the  wild  boar  in  India ;  the 
bovine  bezoar,  found  in  the  gall-bladder 
of  the  ox,  common  in  Nepaul ;  the  camel- 
bezoar,  found  in  the  gall-bladder  of  the 
camel,  and  much  prized  as  a  yellow  paint 
by  the  Hindoos ;  and  the  goat-bezoar, 
produced  from  animals  of  the  goat  kind, 
capra  gazella.  The  Greek  term  for  this 
species  of  concretion  is,  cegagropila,  lite- 
rally, mountain-goat  ball. 

BI,  BINUS  (bis,  twice).  Two;  a  pair. 
Also  a  prefix  of  certain  saline  compounds, 
into  which  two  proportions  of  acid  enter 
for  one  of  base,  as  bi-arseniate. 

1.  Biarticulate.  Having  two  articuli, 
or  joints,  as  applied  to  the  antennae,  or 
to  the  abdomen  of  certain  insects. 

2.  Biauriculate.  Having  two  auricles 
of  the  heart,  as  the  mammalia,  birds, 
reptiles,  and  most  bivalve  mollusca. 

3.  Bicarbonates.  Salts  containing  a 
double  proportion  of  carbonic  acid  gas. 

4.  Bicongregate.  Bigeminate,  or  ar- 
ranged in  two  pairs,  as  the  leaflets  of 
mimosa  unguis  cati. 

5.  Bicrenate.  Doubly  crenate ;  when 
the  crenate  toothings  of  leaves  are  them- 
selves crenate. 

6.  Bidentate.  Two-toothed,  as  applied 
to  the  fruit  or  achenia  of  bidens. 

7.  Biennial.  Enduring  throughout  two 
years  and  then  perishing:  as  plants  which 
bear  only  leaves  the  first  year ;  leaves, 
flowers,  and  fruit  the  second  year,  and 
then  die. 

8.  Bifarious.  Arranged  in  two  rows, 
not  necessarily  opposite  to  each  other; 
in  this  particular,  the  term  is  differenced 
from  distichous. 

9.  Bifoliolate.  "When  two  folioles  or 
leaflets  are  developed  at  the  same  point 
at  the  end  of  the  petiole,  as  in  zygophyl- 
lum  fabago.  The  term  is  synonymous 
with  conjugate. 

10.  Biforines.  Minute  oval  bodies 
found  in  the  leaves  of  some  araceous 
plants.  When  placed  in  water,  they  dis- 
charge innumerable  spicula?  from  each 
extremity,  until  they  become  entirely 
emptied. 

11.  Bifurcate.  Twice-forked,  as  ap- 
plied to  the  inflorescence  of  stellaria, 
and  synonymous  with  dichotomous. 

12.  Bijugous.  In  two  pairs,  as  applied 
to  the  leaflets  of  a  pinnate  leaf. 

13.  Bilabiate.  Having  two  lips,  as 
applied  to  a  calyx  which  has  its  sepals 

D2 


BI 


BIN 


cohering  into  two  parcels,  or  to  a  corolla 
which  has  its  petals  similarly  disposed. 

14.  Bilobate.  Two-lobed,  as  applied  to 
the  leaves  of  bauhinia,  &c. 

15.  Bilocular.  Having  two  loculi  or 
cells,  as  applied  to  the  anther,  and  to 
certain  capsules  in  plants. 

16.  Bimana.  Two-handed;  a  designa- 
tion of  the  first  order  of  the  Mammalia, 
comprising  the  single  species  man,  and 
characterized  by  the  presence  of  hands 
(or  feet  with  opposable  thumbs)  on  the 
upper  extremities  only. 

17.  Bimedial.  In  geometry,  when  two 
lines  commensurable  only  in  power,  as 
the  diagonal  and  the  side  of  a  square, 
are  joined  together,  the  sum  is  irrational 
with  respect  to  either  of  the  two  lines, 
and  is  called  by  Euclid  a  bimedial. 

18.  Binate.  Growing  in  pairs ;  a  term 
synonymous  with  bifoliolate. 

19.  Binervate.  Two-nerved ;  as  ap- 
plied to  the  wings  of  insects  which  are 
supported  by  only  two  nerves. 

20.  Binocular.  That  which  belongs  or 
applies  to  both  eyes,  as  applied  to  a  tele- 
scope, by  which  the  object  maybe  viewed 
with  both  eyes  at  the  same  time. 

21.  Binomial.  An  algebraical  quantity 
consisting  of  two  terms,  as  a  +  A,  or 
2a — 2>bx.  The  binomial  theorem,  first 
announced  by  Newton,  is  a  formula  by 
which  any  binomial  may  be  raised  to  any 
given  power,  without  the  ordinary  pro- 
cess of  involution. 

22.  Biocellate.  Having  two  ocelli  or 
eyelets,  as  applied  to  the  wing  of  an  in- 
sect when  marked  with  two  eye-like 
spots. 

23.  Bipartite.  Parted  in  two,  as  ap- 
plied to  the  segments  of  a  leaf. 

24.  Bipectinate.  When  a  part  has  two 
margins  toothed  like  a  pecten  or  comb. 

25.  Bipeltate.  When  an  animal  or  a 
part  has  a  defence  like  that  of  a  double 
pelta  or  shield. 

26.  Bipinnate.  When  the  leaflets  of  a 
pinnate  leaf  themselves  become  pinnate, 
as  in  fumaria  officinalis. 

27.  Bipupillate.  When  an  eye-like 
spot  on  the  wing  of  a  butterfly  has  two 
pupillae  or  dots  within  it  of  different 
colours. 

28.  Biquadratic.  In  algebra,  the  power 
immediately  succeeding  the  cube;  that 
is,  the  square  of  the  square,  or  the  fourth 
power.  A  biquadratic  equation  is  that 
in  which  the  unknown  quantity  rises  to 
the  fourth,  but  not  to  a  higher  power. 

29.  Biradiate.  Applied  to  a  part  which 
has  two  radii  or  rays. 

52 


30.  Biserial.  Arranged  in  two  series, 
or  rows  ;  a  term  synonymous  with  bifa- 
rious. 

31.  Biserrate.  Doubly  sawed,  as  ap- 
plied to  the  margins  of  leaves,  when  the 
serrations  are  themselves  serrate. 

32.  Bisetous.  When  a  part  is  furnished 
with  two  setae  or  bristle-like  appendages. 

33.  Bisexual.  Applied  to  flowers  which 
contain  both  stamen  and  pistil  in  the 
same  envelope ;  a  term  synonymous  with 
hermaphrodite. 

34.  Bispinose.  When  an  animal  or 
part  is  furnished  with  two  spines. 

35.  Bisulcate.  Applied  to  a  foot  which 
rests  upon  two  sulci  or  hoofed  digits. 

36.  Biternate.  When  three  secondary 
petioles  proceed  from  the  common  pe- 
tiole, and  each  bears  three  leaflets,  as  in 
fumaria  bulbosa. 

37.  Bivalved.  Having  two  valves ; 
applied  to  the  shells  of  certain  mollusca. 

BIBLIO'GRAPHY  {/3t/3\iov,  a  book, 
•ypa'^a),  to  write).  Among  the  ancients 
this  term  denoted  the  writing  or  the 
transcription  of  books.  In  modern  times, 
it  signifies  the  science  of  the  knowledge 
of  books,  with  reference  to  their  authors, 
subjects,  editions,  and  history. 

BICE.  A  blue  colour,  prepared  from 
the  lapis  armenius,  for  painting. 

BILLION.  In  numeration,  a  million  of 
millions,  expressed  by  1,000,000,000,000. 
By  this  term  the  French  signify  only  a 
thousand  millions. 

BI'NARY  COMPOUNDS.  A  series 
of  chemical  compounds,  formed  by  the 
union  of  two  elementary  bodies  with  each 
other  in  their  combining  proportions  only, 
or  in  multiples  of  them,  and  in  no  inter- 
mediate proportions.  If  the  constituents 
of  a  binary  compound  be  represented  by 
A  and  B,  the  latter  being  the  oxygen  or 
electro-negative  constituent,  the  most 
frequent  combination  is  A  +  B,  then 
A  +  2B,  A+3B,  and  A+5B.  The  com- 
bination of  2A4-3B  is  not  unfrequent; 
but  2A+B,  A+4B,  A+7B,  2A+2B,  or 
2A+5B  are  of  comparatively  rare  occur- 
rence. The  five  compounds  of  nitrogen 
and  oxygen  afford  a  good  illustration  of 
this  law  of  combination. 

BI'NARY  NOTATION.  A  kind  of 
notation,  proposed  by  Leibnitz,  in  which 
only  two  characters  are  used,  1  and  0,  the 
zero  having  the  power  of  multiplying  the 
number  it  follows  by  two,  as  in  the  com- 
mon notation  it  multiplies  by  ten.  The 
number  one  is  represented  by  1 ;  two,  by 
10;  three,  by  11;  four,  by  100;  five, 
by  101 ;  six,  by  110  ;  seven,  by  111 ;  eight, 


BIT 


BL  A 


by  1000;  nine,  by  1001;  ten,  by  1010, 
&c. 

BIO'GRAPHY  (/3/of,  life,  ypaftj,  writ- 
ing). That  department  of  literature 
which  treats  of  the  lives  of  individuals. 
It  is  thus  distinguished  from  history, 
which  treats  of  states  and  nations. 

BIRD'S-EYE  VIEW.  A  mode  of 
prone  perspective  representation,  by  which 
objects  are  shown,  in  nature  or  in  paint- 
ing, below  the  spectator,  who  can  see 
them  only  by  looking  down  upon  them. 
The  reverse  of  this  is  the  supine  per- 
spective, termed  di  solto  in  su,  employed 
for  ceiling-pieces,  which  the  spectator 
can  view  only  by  looking  upwards. 

BIRDS'  NESTS,  ESCULENT.  The 
nests  of  the  Hirundo  esculenta,  a  species 
of  swallow  peculiar  to  the  Indian  islands, 
formed  of  a  viscid  substance,  not  unlike 
isinglass.  Nothing  satisfactory  is  known 
as  to  the  formation  of  these  eatable 
nests. 

BI'SMUTH  {wismuth,  German).  A 
reddish-white  metal,  usually  found  in  tin 
mines.  It  occurs  as  an  oxide,  under  the 
name  of  bismuth  ochre;  as  a  sulphuret, 
called  bismuth  glance;  as  a  sulphuret 
with  copper,  called  copper  bismuth  ore; 
and  with  copper  and  lead,  called  needle 
ore.  The  subnitrate  is  known,  in  Phar- 
macy, under  the  name  of  magistery  of 
bismuth.  The  sublimed  oxide  is  known 
by  the  name  of  flowers  of  bismuth  ;  the 
chloride  as  the  butter  of  bismuth.  An 
alloy  of  bismuth,  lead,  and  tin,  consti- 
tutes Newton's  fusible  metal. 

BISSE'XTILE,  or  LEAP-YEAR.  A 
term  adopted  in  the  Julian  calendar. 
Julius  Caesar,  having  ascertained  that 
the  solar  year  consisted  of  365£  days, 
made  the  civil  year  365  days,  and  added 
a  sixth  at  the  end  of  four  years,  to  com- 
pensate for  the  quarter  of  a  day  dropped. 
This  fourth  year,  which  contained  366 
days,  was  termed  bissextile,  from  its 
doubling  the  24th  of  February,  or,  ac- 
cording to  the  Roman  way  of  reckoning, 
the  sextilis,  or  sixth  of  the  calends  of 
March  (bissextus  dies).  This  arrange- 
ment was  denominated  the  Julian  Style, 
or  the  Old  Style,  as  distinguished  from 
the  Gregorian  or  New  Style. 

BISTRE.  A  brown  pigment,  made 
from  the  roots  of  beech  and  other  woods, 
reduced  to  soot,  and  then  boiled  and 
evaporated. 

BITTER  PRINCIPLE.  A  general 
term  applied  to  an  intensely  bitter  sub- 
stance, procured  by  digesting  nitric  acid 
on  silk,  indigo,  &c.  The  bitter  of  Welter 
53 


is  the  former  name  of  picric  or  carbazotic 
acid,  formed  by  the  action  of  nitric  on 
anilic  or  indigotic  acid. 

BITTERN.  The  mother  water,  or  un- 
crystallizable  residue  left  after  muriate 
of  soda  has  been  separated  from  sea-water 
by  crystallization.  It  owes  its  bitterness 
to  sulphate  and  muriate  of  magnesia. 
It  contains  bromine. 

BFTTERSPAR.  Rhombspar.  A  crys- 
talline mineral,  bearing  the  same  relation 
to  dolomite  and  magnesian  limestone, 
that  calcareous  spar  does  to  common 
limestone. 

BITU'MEN  {wlrvna,  TrtTt/f,  pine).  A 
mineral  pitch,  supposed  to  be  formed  in 
the  earth  by  the  decomposition  of  animal 
and  vegetable  substances.  In  its  most 
fluid  state  it  constitutes  naphtha;  when 
of  the  consistence  of  oil,  it  becomes  petro- 
leum ;  at  the  next  stage  of  induration  it 
becomes  elastic  bitumen;  then  maltha; 
and  so  on  until  it  becomes  a  compact 
mass,  and  is  then  called  asphaltum. 

BITU'MINOUS  SHALE.  An  argil- 
laceous shale,  much  impregnated  with 
bitumen,  which  gives  it  a  dark  brown  or 
blackish  colour;  its  structure  is  slaty, 
the  streak  brown  and  shining. 

BPVALVE  (bis,  twice,  valvce,  folding- 
doors).  A  shell  which  has  two  valves, 
belonging  to  the  order  Dithyra. 

BLACK  COMPOUNDS.  1.  Black 
lead,  or  plumbago,  is  a  carburet  of  iron, 
found  in  a  pure  state  only  at  Borrowdale 
in  Cumberland.  It  derives  its  name  from 
its  leaden  appearance,  for  it  does  not 
contain  a  particle  of  lead.  2.  Black  dye 
is  a  compound  of  oxide  of  iron  with  gallic 
acid  and  tannin.  3.  Black  flux  is  a  mix- 
ture of  charcoal  and  carbonate  of  potash. 
4.  Black  chalk  is  a  mineral  found  in 
primitive  mountains,  and  sometimes  near 
coal  formations.  5.  Black  jack  is  the 
technical  term  for  blende  or  mock  lead, 
an  ore  of  zinc.  6.  Black  wadd  is  an  ore 
of  manganese,  called  the  black  oxide, 
and  used  as  a  drying  ingredient  in  paints. 
7.  Black  turpeth  is  the  protoxide  of  mer- 
cury, commonly  called  the  gray,  ash,  or 
black  oxide.  8.  Lamp  black  is  a  species 
of  charcoal  procured  by  burning  resinous 
substances  in  a  furnace.  9.  Spanish  black 
is  also  a  charcoal  made  of  burnt  cork, 
and  first  used  by  the  Spaniards.  10.  Black 
salts,  is  the  name  given  in  America  to 
wood-ashes,  after  they  have  been  lixi- 
viated, and  the  solution  evaporated,  until 
the  mass  has  become  black. 

BLADDER  GREEN.  A  green  pig- 
ment, prepared  from  the  ripe  berries  of 
D3 


B  LE 


BL  U 


the  Rhamnus  catharticus,  or  Buck- 
thorn, mixed  with  gum  arabic  and  lime 
water. 

BLANCHING.  Etiolation.  The  pro- 
cess of  whitening  the  leaves  and  stems 
of  plants,  by  excluding  the  light,  and 
thus  preventing  the  development  of  their 
natural  properties. 

BLANK  VERSE.  Verse  without 
rhyme  or  the  consonance  of  final  syl- 
lables! 

BLASTE'MA  (/3\a<rTa'va>,  to  bud).  A 
Greek  term  applied  to  the  rudimental 
mass  of  an  organ  in  the  state  of  forma- 
tion ;  it  is  said  to  consist  of  fluid,  nucle- 
ated cells,  and  granules  which  spontane- 
ously change  into  cells  and  into  nuclei  of 
cells.  Botanical  writers  apply  the  term 
to  the  thallus  of  lichens;  according  to 
Mirbel,  the  blastema  comprises  the  ra- 
dicle, plumule,  and  caulicle  of  the  em- 
bryo. 

BLASTOCA'RPOUS  (/?\ac~r6r,  a  shoot, 
Kapnot,  fruit).  A  term  applied,  in  Bo- 
tany, to  those  plants  in  which  germina- 
tion takes  place  within  the  fruit  before 
it  fells,  as  in  the  mangrove. 

BLA'STUS  (fiXaaros,  a  shoot).  A  term 
sometimes  applied  to  the  plumule  of 
grasses.  With  the  same  idea,  Richard 
considers  the  scutelliform  cotyledon  of 
these  plants  to  be  a  particular  modifica- 
tion of  the  radicle,  and  calls  it  hypo- 
blastus ;  the  anterior  occasional  cotyledon 
he  views  as  a  peculiar  appendage,  and 
names  it  epiblastus ;  the  radicle  is  a  pro- 
tuberance of  the  caulicle,  and  termed 
radiculoda.  Finally,  to  embryos  of  this 
description  he  gives  the  general  designa- 
tion of  macropodal.  Dr.  Lindley  observes 
that  in  these  ideas  Richard  was  wrong, 
as  is  now  well  known. 

BLA'TTID^.  A  family  of  Ortho- 
pterous  insects,  named  from  the  genus 
blatta,  a  familiar  species  of  which  is 
known  under  the  vernacular  term  cock- 
roach. 

BLEACHING.  The  chemical  process 
of  whitening  linen  or  woollen  stuffs. 
1.  Linen  is  bleached,  by  the  old  process, 
by  exposure  to  air  and  moisture  ;  by  the 
new  process,  by  means  of  chlorine  or 
solution  of  chloride  of  lime.  2.  Woollen 
stuffs  are  bleached  by  soap  and  water, 
which  is  called  the  Natural  Method ;  or 
by  exposure  to  the  vapour  of  sulphur, 
which  is  commonly  called  bleaching  by  the 
flower,  or  bleaching  of  Paris,  because  this 
method  is  employed  in  that  city  more 
than  elsewhere. 

BLEACHING  POWDER.  Chloride 
54 


of  lime,  prepared  by  exposing  hydrate 
of  lime  gradually  to  chlorine  gas.  This 
compound  is  obtained  in  solution  by 
transmitting  a  stream  of  chlorine  gas 
through  hydrate  of  lime  suspended  in 
water,  and  the  solution  is  tnen  called 
bleaching  liquid,  or  oxymuriatic  alkaline 
water. 

BLENDE.  A  term  signifying  a  mine- 
ral which  contains  no  ore,  particularly 
applied  to  the  native  sulphuret  of  zinc, 
but  extended  by  mineralogists  to  other 
substances,  as  manganese-blende,  anti- 
mony-blende, ruby-blende,  &c. 

BLETTING.  A  term  adapted  by  Dr. 
Lindley  to  denote  that  peculiar  bruised 
appearance  in  some  fruits,  called  blessi 
by  the  French,  for  which  we  have  no 
equivalent  English  expression. 

BLIGHT,  A  popular  name  for  various 
diseases  of  plants.  These  diseases  are 
probably  owing  to  arrest  of  the  natu- 
ral functions  of  plants  by  circumstances 
depending  on  temperature  and  the  con- 
ditions of  the  atmosphere. 

BLO'EDITE.  A  massive  translucent 
salt,  found  at  Ischel  in  Upper  Austria, 
together  with  prismatic  gypsum. 

BLOODSTONE.  Haematites.  A  green 
agate  coloured  by  chlorite,  with  nume- 
rous red  spots  like  drops  of  blood  ;  called 
also  heliotrope  and  oriental  jasper. 

BLOW-PIPE.  A  small  conical  tube, 
bent  at  one  end,  so  as  to  be  easily  intro- 
duced into  the  flame  of  a  candle  or  lamp, 
for  the  purpose  of  directing  a  stream  of 
flame,  by  blowing  through  it,  upon  any 
object  which  is  to  be  heated. 

Oxy-hydrogen  Blow-pipe.  An  apparatus 
for  producing  intense  heat,  by  supplying 
a  stream  of  hydrogen  with  pure  oxygen, 
so  that  the  two  gases  issue  together  in 
the  form  of  a  jet  from  the  nozzle  of  the 
blow-pipe. 

BLUE  COMPOUNDS.  1.  Prussian 
or  Berlin  blue  is  the  sesquiferricyanide 
of  iron  ;  basic  Prussian  blue  is  a  com- 
pound of  Prussian  blue  and  peroxide  of 
iron.  2.  Saxon  blue  is  a  sulphate  of  in- 
digo, or  a  solution  of  indigo  in  concen- 
trated sulphuric  acid.  3.  Blue  verditer  is 
an  impure  carbonate  of  copper  ;  blue  cop- 
per ore  is  the  finely  crystallized  subcar- 
bonate  of  copper.  4.  TurnbulVs  blue  is 
the  ferricyanide  of  iron,  precipitated  on 
adding  red  prussiate  of  potash  to  a  proto- 
salt  of  iron.  5.  Blue  vitriol,  copperas, 
or  blue  stone,  is  the  sulphate  of  copper, 
prepared  by  roasting  and  oxidating  the 
sulphuret  of  copper.  6.  Blue  John  is  a 
technical  name  for  fluor  or  Derbyshire 


BOM 


BOR 


spar.    7.  Blue  black  is  another  name  for 
ivory  black. 

BLUFFS.  A  term  employed  in  the 
United  States  to  designate  high  banks 
presenting  a  precipitous  front  to  the  sea 
or  a  river. 

BODY.  A  term  applied  in  Physics  to 
any  determinate  part  of  matter,  but  of 
itself  utterly  passive,  capable  of  any  sort 
of  motion,  and  of  all  figures  and  forms. 
Body,  or  substance,  which  is  the  same 
thing,  is  usually  denoted  by  the  general 
term  matter.  Its  forms  are  the  solid,  as 
crystals ;  and  the  fluid,  which  are  elastic 
and  aeriform,  as  gases,  or  inelastic  and 
liquid,  as  water.  In  Geometry,  the  term 
body  is  synonymous  with  solid. 

BOG-EARTH.  An  earth  composed 
of  light  siliceous  sand  and  about  25  per 
cent,  of  vegetable  fibre  in  a  decomposing 
state. 

BOG  IRON  ORE.  A  ferruginous  de- 
posit, occurring  at  the  bottom  of  peat 
mosses  and  in  marshy  places,  owing  to 
the  presence  of  oxide  of  iron  in  solution 
in  almost  all  water.  These  ferruginous 
matters  sometimes  form,  below  the  soil, 
a  plate,  or  pan,  which  is  impermeable  to 
the  roots  of  trees. 

BOILING  POINT.  That  degree  in 
the  scale  of  the  thermometer,  at  which 
ebullition  is  produced  under  the  medium 
pressure  of  the  atmosphere.  Thus,  212° 
is  the  boiling  point  of  water,  when  the 
barometer  stands  at  30  inches ;  at  31 
inches,  it  is  21376;  at  29,  it  is  only  210*19; 
in  a  common  vacuum,  it  is  70°. 

BOLE  (/3S>\or,  a  mass).  A  friable 
earthy  substance,  a  species  of  the  soap- 
stone  family.  It  is  found  in  Lemnos, 
and  is  hence  termed  Lemnian  earth ;  also 
in  Armenia,  France,  and  other  places. 
Its  colours  are  yellow -red,  and  brownish- 
black,  when  it  is  called  mountain  soap. 

BOLE'TIC  ACID.  An  acid  procured 
from  the  expressed  juice  of  the  Boletus 
pseudo-igniarius,  a  species  of  mush- 
room. 

BOLO'GNIAN  STONE.  Native  sul- 
phate of  barytes;  a  phosphoric  stone 
found  at  Bologna.  When  heated  with 
charcoal,  it  becomes  a  powerful  solar 
phosphorus. 

BOMBIC  ACID  (poupvf,  the  silk- 
worm). An  acid  contained  in  a  reservoir 
near  the  apus  of  the  silk-worm.  It  forms 
salts  with  the  alkalies,  earths,  and  me- 
tallic oxides,  which  have  been  called 
bombiate8. 
BOMBY'CIDjE  (bombyx,  the  silk- 
55 


worm).  A  tribe  of  Lepidopterous  insects, 
named  from  the  genus  Bombyx,  and 
consisting  of  Moths  allied  to  the  common 
silk-worm.  The  principal  characteristics 
of  the  family  are  the  presence  of  merely 
rudimentary  maxillae,  remarkably  small 
palpi,  and  bipectinated  antennae. 

BOMBY'LIDjE.  A  family  of  Dipterous 
insects,  named  from  the  genus  Bomby- 
lius,  and  distinguished  chiefly  by  their 
long  proboscis. 

BONE  EARTH.  The  residue  of  bones 
which  have  been  calcined,  and  converted 
into  a  friable  substance,  consisting  chiefly 
of  phosphate  of  lime. 

BOOTES.  A  northern  constellation, 
containing  fifty-four  stars,  the  principal 
of  which  is  Arcturus. 

BORA'CIC  ACID.  An  acid  compound 
of  boron  and  oxygen,  formerly  called 
Romberg's  sedative  salt  and  sedative  salt 
of  borax.  It  occurs  native  on  the  edges 
of  hot  springs  in  Florence,  &c,  in  small 
pearly  scales,  and  also  in  a  massive 
state.  It  forms  salts  with  bases,  which 
are  called  borates,  of  which  the  only  im- 
portant one  is  borax. 

BO'RACITE.  A  mineral  consisting 
of  an  anhydrous  compound  of  magnesia 
and  boracic  acid,  in  the  extraordinary 
ratio  of  3  equivalents  of  the  former  to  4 
of  the  latter.  The  rare  mineral  hydro- 
boracite  is  said  to  be  a  compound  of  a 
borate  of  lime  and  borate  of  magnesia, 
in  both  of  which  the  acid  and  the  base 
are  in  the  same  ratio  as  in  boracite,  with 
18  equivalents  of  water. 

BORAGINA'CEjE.  The  Borage  tribe 
of  Dicotyledonous  plants.  Herbaceous 
plants  or  shrubs,  with  leaves  alternate, 
covered  with  asperities ;  corolla  gamo- 
petalous;  stamens  inserted  in  the  corolla; 
fruit,  four  nuts,  distinct. 

BORAX  {baurach,  Arab.)-  A  native 
bi-borate  of  soda,  chiefly  found  in  an  im- 
pure state,  and  then  called  tinkal,  or 
rough  borax,  as  a  saline  incrustation  in 
the  beds  of  certain  small  lakes  in  an  up- 
per province  of  Thibet.  When  the  re- 
fined salt  is  deprived  of  its  water  of 
crystallization  by  fusion,  it  forms  a  vi- 
treous transparent  substance,  called  glass 
of  borax. 

BOREAL  SIGNS.  Those  on  the  north 
side  of  the  equinoctial ;  viz.  Aries,  Tau- 
rus, Gemini,  Cancer,  Leo,  and  Virgo. 

BORNEEN.  The  name  given  to  a 
compound  of  carbon  and  hydrogen  found 
in  valeric  acid,  supposed  to  be  identical 
with  liquid  camphor. 

D4 


BOTANY. 


BO'RON.  An  elementary  substance, 
somewhat  analogous  to  carbon,  always 
found  in  combination  with  oxygen  as  bo- 
racic  acid,  from  which  it  was  first  ob- 


tained by  Davy  by  the  action   of  the 
voltaic  battery. 

BO'RURET.    A  compound  of  the  ele- 
ment boron  with  a  metal. 


BOTANY  (/3oTai/n,  a  plant).  The  science  which  treats  of  the  Vegetable  King- 
dom. 1.  Structural  Botany  relates  to  the  laws  of  vegetable  structure,  internal  or 
external,  independently  of  the  presence  of  a  vital  principle.  2.  Physiological 
Botany  relates  to  the  functions  of  plants  and  their  changes  in  disease  or  health. 

3.  Descriptive  Botany    relates    to    the    description    and   nomenclature    of  plants. 

4.  Systematic  Botany  relates  to  the  principles  upon  which  plants  are  connected  with, 
and  distinguished  from,  one  another. 

I.  SYSTEM  OF  LINSMEUS. 

1.  Classes.— Plants  are  distributed  into  twenty-four  classes,  founded  on  the  num- 
ber, position,  and  relative  connexion  of  the  sexual  organs.  Of  these  classes,  the 
first  twenty  have  hermaphrodite  flowers  ;  the  following  three,  unisexual  flowers  ;  the 
last  has  no  flowers.  The  first  eleven  classes  are  founded  on  the  number  of  the 
stamens ;  the  12th  and  13th,  on  their  number  and  position;  the  14th  and  15th,  on 
their  number  and  relative  length;  the  16th,  17th,  and  18th,  on  modes  of  connexion 
subsisting  between  the  filaments  of  the  stamens;  the  19th,  on  connexion  of  the 
anthers  of  the  stamens;  the  20th,  on  connexion  of  the  stamens  with  the  pistil ;  the 
•21st,  22nd,  and  23rd,  on  modifications  arising  from  unisexuality  and  hermaphroditism; 
the  24th,  on  the  absence,  or  obscure  nature,  of  the  sexual  organs,  as  compared  with 
those  of  all  the  other  classes. 

2.  Orders. — The  classes  are  distributed  into  orders,  the  first  thirteen  classes  being 
divided,  each,  into  several  orders  depending  on  the  number  of  the  styles ;  the  14th, 
into  two  orders,  the  seeds,  in  the  one,  being  covered  by  a  seed-vessel,  those  in  the 
other  being,  as  Linnaeus  erroneously  supposed,  naked;  the  15th,  into  two  orders, 
the  one  characterized  by  a  long  seed-vessel,  or  siliqua,  the  other  by  a  short  one,  or 
silicula;  the  16th,  17th,  and  18th,  into  several  orders  founded  on  the  number  of  the 
stamens;  the  19th,  into  three  orders  relating  to  the  unisexual,  hermaphrodite,  or 
neutral  condition  of  the  florets ;  the  20th,  21st,  and  22nd,  into  several  orders 
dependent  on  the  number  and  modes  of  connexion  of  the  stamens ;  the  23rd  into 
three  orders  founded  on  unisexuality  and  hermaphroditism;  the  24th,  on  general 
natural  affinities.  This  and  the  preceding  paragraph  may  be  studied  in  connexion 
with  the  tables  on  the  two  following  pages. 


CLASSES  OF  THE  LINN^EAN  SYSTEM. 
•Class 

1.  Monandria  1  S tamen  in  each  flower. 

2.  Diandria  2  Stamens  equal  in  length. 

3.  Triandria 3       „  „ 

4.  Tetrakdria  4   „      „ 

5.  Pentandria 5   ,,      ,, 

6.  Hexandria  6   ,,      ,, 

7.  Heptandria 7        „  ,, 

8.  Octandria 8       ,,  „ 

9.  Enneandria 9        ,,  ,, 

10.  Decandria  10        „  ,, 

11.  DODECANDRIA  12  to  19  „ 

12.  Icosandria  20  or  more,  on  the  calyx. 

13.  Polyandria 20  or  more,  on  the  receptacle. 

14.  Didykamia  4;  2  long,  2  short. 

15.  Tetradynamia  ....  6;  4  long,  2  short ;  flowers  cruciform. 

16.  Monadelphia Filaments  united  at  the  base  into  one  set. 

17.  Diadelphia Filaments  united  into  two  sets. 

18.  Polyadelphia  Filaments  united  in  to  three  or  more  sets. 

19.  Syngenesia Anthers  united.    Flowers  compound. 

\  20.  Gynandria  Stamens  inserted  on  the  Pistil 

56 


BOTANY. 

CLASSES  OF  THE  LINNjEAN  SYSTEM  (continued). 
/Class 

u3   I      21.  Moncecia  Stamens  and  Pistils  in  separate  flowers  on  the 

&  g    I  same  plant. 

^  xj  y     22.  Dicecta    Stamens  and  Pistils  in  separate  flowers  on  two 

jfW  \  separate  plants. 

3g    j     23.  Polygamia    Stamens  and  Pistils  separate  in  some  flowers, 

p    I  united  in  others,  either  on  the  same  plant,  or 

V  on  tfwo  or  f/jree  distinct  plants. 

24.  Cryptogamia  Fructification  concealed. 


ORDERS  OF  THE  LINN^EAN  SYSTEM. 

1.  The  Orders  of  the  first  thirteen  Classes  are  founded  on  the  number  of  styes 

1.  Monogynia,  1  style.  6.  Hexagynia,  6  styles. 

2.  Digynia,  2  styles.  7.  Heptagynia,  7  styles. 

3.  Trigynia,  3  styles.  8.  Octogynia,  8  styles. 

4.  Tetragynia,  4  styles.  9.  Decagynia,  9  styles. 

5.  Pentagynia,  5  styles.  10.  Polygyria,  many  styles. 


2.  The  Orders  of  the  fourteenth  Class  are  two,  founded  on  the  presence  or  (sup- 
posed) absence  of  a  seed-vessel : — 

1 .  Gymnospermia,  seeds  4,  apparently  naked ;  or  ovarium  4-lobed. 

2.  Angeiospermia,  seeds  in  a  distinct  seed-vessed. 


3.  The  Orders  of  the  fifteenth  class  are  two,  founded  on  the  comparative  length 
of  the  seed-vessel : — 

1.  Siliquosa,  seeds  in  a  long  seed-vessel,  or  siliqua. 

2.  Siliculosa,  seeds  in  a  short  seed-vessel,  or  silicula. 


4.  The  Orders  of  the  sixteenth,  seventeenth,  and  eighteenth  Classes  are  founded 
on  the  number  of  stamens  in  each  adelphia,  or  brotherhood  :— 

1.  Triandria,  3  stamens.  3.  Decandria,  10  stamens. 

2.  Pentandria,  5  stamens.  4.  Polyandria,  many  stamens. 


5.  The  Orders  of  the  nineteenth  Class  are  founded  on  the  structure  of  the  flower  :— 

1.  JEqualis,  all  the  florets  perfect. 

2.  Superflua,  florets  of  the  disk  perfect ;  of  the  ray,  pistilliferous  only. 

3.  Frustranea,  florets  of  the  disk  perfect ;  those  of  the  ray  neuter. 


6.  The  Orders  of  the  twentieth  Class  are  founded  on  the  number  of  the  stamens  :- 
1.  Monandria,  1  stamen.  2.  Diandria,  2  stamens,  &c. 


The  Orders  of  the  twenty-first  and  twenty-second  Classes  are  founded  on  the 
number,  union,  and  situation  of  the  stamens  : — 
1.  Monandria,  1  stamen.      2.  Diandria,  2  stamens.       3.  Monadelphia,  &c. 


8.  The  Orders  of  the  twenty-third  Class  are  three,  founded  on  the  separation  of 
the  sexes  in  the  same  plant,  or  in  different  plants  : — 

1.  Moncecia,  unisexual  flowers  accompanied  by  barren  or  fertile  flowers,  or 
,  both,  all  on  one  plant. 

2.  Dicecia,  the  same,  on  two  different  plants. 

3.  Tricecia,  the  same,  on  three  different  plants 


9.  The  Orders  of  the  twenty-fourth  Class  are  Natural  orders,  or  Families  :— 
•  1.  Fiiices.    2.  Musci.    3.  Hepaticce.    4.  Lichenes.    5.  Fungi.     6.  Alga. 
57  D5 


BOTANY. 

II.  NATURAL  SYSTEM. 

Class  I. — Exogens,  or  Dicotyledonous  Flowering  Plants. 

Leaves  reticulated.  Stem  with  bark,  wood,  medullary  rays,  and  pith ;  increasing  in 
diameter  by  the  addition  of  new  matter  to  the  exterior.  Flowers  with  a  quinary,  or 
more  rarely  a  quaternary,  division.  Seeds  in  a  pericarp.  Cotyledons  two,  opposite ; 
or,  if  more,  whorled,  or  on  the  same  plane.     Germination  exorrhizous. 

1.  Divisions  of  Jussieu.— The  primary  divisions  are  founded  on  the  separation, 
the  combination,  and  the  absence  of  the  petals,  and  are  termed  the  polypetalous,  the 
monopetalous,  and  the  apetalous  groups;  to  which  is  added  a  fourth,  founded  on  the 
separation  of  the  sexes  in  flowers  having  no  petals,  and  termed  diclinous.  The  first 
three  are  divided  with  reference  to  the  insertion  of  the  stamens,  which  are  epi- 
gynous,  perigynous,  or  hypogynous  ;  further,  the  monopetalous  epigynous  group  is 
subdivided  into  plants  which  have  their  stamens  united  and  those  which  have  them 
distinct.    Hence  we  have  eleven  classes  : — 

Class. 

{Stamens  epigynous 1 
Stamens  perigynous  2 
Stamens  hypogynous  3 

!  Corolla  hypogynous 4 

Monopetalous      ^rolla  perilous  333^-35^    J 
^Corolla  epigynous     {Anthers  distinct  7 

{Stamens  epigynous 8 
Stamens  perigynous  9 
Stamens  hypogynous 10 

Diclinous  11 

2.  Divisions  of  De  Candolle. — De  Candolle  reduced  the  eleven  classes  of  Jussieu 
to  four ;  the  first  three  being  founded  on  the  separation  or  cohesion  of  the  several 
parts  of  the  flower,  the  fourth  on  the  suppression  of  the  floral  envelopes.  Thus,  in 
Thalamiflorae,  all  the  parts  are  present  and  distinct  from  each  other;  in  Calyciflorae, 
the  stamens  adhere  to  the  calyx ;  in  Corolliflorae,  the  petals  cohere  with  each  other; 
in  Monochlamydeae,  the  corolla  is  suppressed,  and,  in  the  most  imperfect  orders,  the 
calyx  also. 

PnlvnPtalmn  /  Stamens  hypogynous Thalami force. 

roiypeiaious  I  Stamens  perigynous  Calyciflora. 

Monopetalous Corollifiorce. 

Apetalous Monochlamydece. 

3.  Divisions  of  Dr.  Lindley.  —  Dr.  Lindley  first  distributes  the  Class  into  the 
Polypetalous,  Monopetalous,  and  Incomplete  sub-classes;  these  are  next  divided 
into  groups.  The  principles  on  which  these  divisions  are  founded  are  stated  in  the 
following  table : — 

Table  of  Groups. 
Sub-class  I.    Polypetalae.  Groups. 

Albumen  very  considerably  larger  than  the  minute  embryo  Albuminosce. 

Albumen  absent,  or  only  forming  a  layer  between  the  embryo  and 
the  seed-coat. 

Ovary  inferior  (often  with  an  epigynous  disk) Epigynosce. 

Ovary  superior. 

Placentae  parietal Parietosce. 

Placentae  in  the  axis. 

Calyx  dislocated   Calycosce. 

Calyx  complete ;  its  parts  being  all  on  the  same  plane. 
Carpels  united  into  a  solid  pistil,  parallel  with 

each  other  Syncarposce. 

Carpels  oblique,  upon  a  gynobase Gynobaseosce. 

Carpels  disunited Apocarposce. 

58 


BOTANY. 

Sub-class  II.    Incompletae,  or  Apetalae. 

Calyx  altogether  absent Achlamydosce. 

Calyx  present. 

Embryo  curved  round  albumen Curvembryosce. 

Embryo  straight. 

Stamens  monadelphous Columnosa. 

Stamens  distinct. 

Calyx  tubular,  often  corolliform  Tubiferoscc. 

Calyx  very  imperfect Rectembryosee. 

Sub-class  III.    Monopetalae. 

Fruit  consisting  of  but  one  perfect  carpel Aggregosce. 

Fruit  of  several  carpels. 

Ovary  inferior Epigynosce. 

Ovary  superior. 

Carpels  three  or  more Polycarposce. 

Carpels  only  two. 

Fruit  nucamentaceous    Nucamentoscs. 

Fruit  capsular  Dicarposce. 

Class  II. — Endogens,  or  Monocotyledonous  Flowering  Plants. 

Leaves  straight-veined.  Stem  increasing  in  diameter  by  the  addition  of  new  matter 
to  the  centre.  Flowers  with  a  ternary  division.  Embryo  with  one  cotyledon.  Germi- 
nation endorrhizous. 

Divisions  of  Br.  Lindley. — There  are  two  primary  divisions,  one  having  the 
organization  of  the  flowers  perfect,  i.  e.  with  a  distinct  calyx  and  corolla,  and  a 
regular  consolidated  cotyledon ;  the  other  imperfect,  the  calyx  and  corolla  being 
either  entirely  absent,  or  in  an  incomplete  condition,  and  the  cotyledon  being  com- 
monly rolled  up  without  consolidation,  or  actually  flat.  The  former  includes  four 
groups,  the  latter  two,  the  characters  of  which  are  stated  in  the  following  table : — 

Perfect  Endogens. 

Group  I.—Epigynos^:.    Anthers  distinct.    Flowers  complete,  formed  upon  a  ter- 
nary plan.    Ovary  inferior ;    or,  if  superior,  then  the  leaves  either 
scurfy  or  equitant. 
Zingiberaceae.   Musaceae.   Haemodoraceae.   Taccaceae.  Bromeliaceae 
Marantaceae.    Amaryllidaceae.    Burmanniaceae.    Iridaceae.    Hydro- 
characeae. 
Group  2. — Gynandros-s:.    Stamens  and  style  consolidated  into  a  central  column. 
Flowers  complete,  formed  upon  a  ternary  plan.    Ovary  inferior,  usually 
once-celled,  with  scobiform  seeds. 
Orchidaceae.    Vanillaceae.    Apostasiaceae. 
Group  3. — Hypogynos-e:.    Flowers  coloured,  formed  upon  a  ternary  plan.    Ovary 
superior. 
Palmaceae.    Melanthaceae.    Liliaceae.    Butomaceae.    Juncaceae. 
Pontederaceae.    Gilliesiaceae.    Commelinaceae.     Alismaceae.    Phily- 
draceae. 
Group  4. — Retos-e.    Leaves  either  with  many  ribs,  the  intervals  between  which  are 
irregularly  netted,  or  with  a  midrib  and  netted  sides  ;  foot-stalk  taper, 
articulated  with  the  stem.     Embryo  without  a  lateral  slit.    Flowers 
never  arranged  in  a  spadix.    Floral  envelopes  complete. 
Smilaceae.    Dioscoreaceae.    Roxburghiaceae. 

Imperfect  Endogens. 

Group  5.— Spadicosje.    Flowers  herbaceous  or  imperfect ;  the  perianth  sometimes 
absent.    Embryo  with  a  lateral  slit  for  the  emission  of  the  plumule. 
Pandanaceae.     Araceae.     Typhaceae.     Juncaginaceae. 
Cyclauthacese.    Acoraceae.    Naiadaceae.    Pistiaceae. 
"59  D  6 


BOU 


BRA 


Group  6.— Glumos;e.    Bract  scale-like,  glumaceous,  imbricated,  in  the  room  of  a 
calyx. 

Graminaceae.    Desvauxiaceae. 
Cyperacese.    Restiaceae.     Xyridaceae. 

Class  III. — Acrogens,  Cryptogamic,  or  Flowerless  Plants. 

Plants  usually  composed  of  cellular  tissue  only.     Stem,  when  such  exists,  increasing 
by  extension  of  its  point.     Reproduction  taking  place  either  by  spores  inclosed  in 
thecce,  or  imbedded  in  the  substance  of  the  plant.     Germination  occurring  at  any  part 
of  the  surface  of  the  spore. 
Sub-class  1. — iETHEOGAMOus.    Plants  furnished  with  air-vessels  and  stomates. 

Filices.    Marsiliaceae.    Lycopodiaceae. 

Equisetaceae.     Salviniaceae.     Marchantiaceae.    Jungermanniaceae. 
Sub-class  2. — Amphigamous.    Plants  having  neither  air-vessels  nor  stomates. 

Characeae.    Andraeaceae.     Fungaceae. 

Musci.    Lichenaceae.    Algaceae. 


BOTANY  BAY  RESIN.  An  aro- 
matic resin  which  exudes  from  the  trunk 
of  the  Acarois  resinifera  of  New  Hol- 
land. 

BOTHRE'NCHYMA  (/360pot,  a  pit, 
eixvfxa,  enchyma).  A  name  recently  ap- 
plied in  Botany  to  the  pitted  tissue  or 
dotted  ducts  of  former  writers,  the  appear- 
ance of  these  tubes  being  occasioned  by 
the  presence  of  little  pits  sunk  in  their 
walls.  It  is  either  articulated  or  conti- 
nuous. 

BOTRY'LLARIjE  (poTpvs,  a  bunch  of 
grapes).  A  group  of  the  tunicated  mol- 
lusca,  in  which  the  individuals  con- 
sist of  small  ovoid  bodies,  which  attach 
themselves  to  sea-weed  or  other  sub- 
stances in  regular  bunches,  arranged 
like  the  rays  of  a  star  around  a  common 
centre. 

BOTRY'LLI  (/SoTpv?,  a  bunch  of 
grapes).  A  little  cluster  of  berry-shaped 
bodies. 

BOTRYOI'DAL  (/36tPu?,  a  bunch  of 
grapes,  ctdor,  likeness).  Clustered,  like 
a  bunch  of  grapes. 

BO'TRYOLITE  (/3eTpur,  a  bunch  of 
grapes,  \i0os,  a  stone).  A  mineral  oc- 
curring in  botryo'idal  masses,  in  a  bed  of 
gneiss  near  Arendahl  in  Norway,  and 
considered  by  some  writers  as  a  variety 
of  datholite.     Its  basis  is  boron. 

BOULDERS.  Erratic  Blocks.  A 
provincial  term  for  large  rounded  blocks 
of  stone  lying  on  the  surface  of  the 
ground,  or  sometimes  imbedded  in  loose 
soil,  different  in  composition  from  the 
rocks  in  their  vicinity ;  hence  it  appears 
that  they  have  been  transported  from  a 
distance. 

BOURGEON;  BOUTON.  Terms  ap- 
plied by  French  botanists  to  the  leaf-bud 
60 


and  the  flower-bud,  respectively,  of  Eng- 
lish writers. 

BOUSTROPHE'DON  (fioZs,  an  ox, 
<rTpe<pu>,  to  turn).  A  term  descriptive  of 
a  mode  of  writing  alternately  from  left  to 
right  and  from  right  to  left,  from  its  re- 
semblance to  the  mode  of  making  fur- 
rows in  ploughing  a  field.  Some  speci- 
mens occur  among  the  Arundelian 
marbles  at  Oxford. 

BOVEY  COAL.  Brown  Coal.  A  va- 
riety of  coal  found  at  Bovey  Heathfield, 
near  Exeter.  It  consists  of  wood  pene- 
trated with  petroleum,  sometimes  con- 
taining pyrites,  alum,  and  vitriol. 

BO'VIDJE  (bos,  bovis,  an  ox).  The 
Ox  tribe;  a  family  of  the  Ruminantia, 
in  which  the  horns  are  directed  upwards 
and  forwards,  and  increase  by  layers 
during  life. 

BOYLE'S  FUMING  LIQUOR.  Hy- 
dro-sulphuret  of  ammonia,  or  volatile 
liver  of  sulphur.     See  Fuming  Liquor. 

BRA'CCATE  (bracca,  breeches).  A 
term  applied  to  the  feet  of  birds  when 
concealed  by  long  feathers  descending 
from  the  tibia. 

BRACHELY'TRA  {/3PaXv?,  short,  $\v- 
rpov,  a  wing-case).  A  family  of  the  pen- 
tamerous  Coleoptera,  characterized  by  the 
presence  of  four  palpi,  and  by  the  short- 
ness of  the  wing-cases.  The  staphylinus 
is  the  only  genus  of  the  family. 

BRA'CHIATE  (brachium,  an  arm). 
A  term  applied  in  Botany  to  branches 
which  diverge  nearly  at  right  angles  from 
the  stem. 

BRACHIO'PODA  (foaxiw,  an  arm, 
n-ouf,  Trodop,  a  foot).  A  division  of  the 
Mollusca,  so  named  by  Cuvier  from  their 
having  two  long  spiral  arms  placed  on 
each  side  of  the  mouth,  which  in  many 


BRA 


BRE 


species  can  be  unrolled  to  a  considerable 
length,  and  protruded  to  some  distance, 
in  search  of  aliment.  See  Palliobran- 
chiata. 

BRACHI'STOCHRONE  (/?Pdx«rrcK, 
shortest,  xp°vo?,  time).  The  name  given 
by  Bernouilli  to  a  particular  curve,  by 
which  a  body  arrives  at  a  given  point  in 
a  shorter  time  than  if  it  followed  any  other 
direction. 

BRA'CHIUM.  The  arm.  The  second 
segment  of  the  anterior  extremity  of  the 
lower  mammalia.  The  brachia  of  insects 
are  the  first  pair  of  legs  in  the  hexapods, 
the  direction  of  which  is  usually  towards 
the  head. 

BRACHY'PTEROUS  (/3paXvv,  short, 
Trrepov,  a  wing).  A  term  applied  to  birds 
whose  folded  wings  do  not  reach  the  base 
of  the  tail. 

BRACHYU'RA  (/3paXv?,  short,  ovpa, 
a  tail).  A  family  of  Decapods,  distin- 
guished by  the  shortness  of  the  tail,  as 
in  the  common  crab. 

BRACT  {bractea,  a  thin  leaf  or  plate 
of  any  metal).  A  term  applied  to  the 
flower-leaf,  or  that  leaf  from  whose  axil 
the  flower-bud  is  developed.  These  are 
the  leaves  which  composse  the  involu- 
crum  of  the  Compositae,  the  glumes  of 
Graminaceae,  the  spathe  of  Araceae,  &c. 
But  the  term  is  extended  to  all  those 
modifications  of  leaves  which  are  found 
upon  the  inflorescence,  and  are  situated 
between  the  true  leaves  and  the  calyx  of 
the  flower.  These  are  termed  by  some 
writers  bracteolce,  or  bractlets. 

BRA'NCA'S  WHEEL.  A  machine 
contrived  by  Giovanni  Branca,  in  1629, 
for  raising  water,  and  other  purposes. 
It  consists  of  a  wheel  furnished  with  flat 
vanes  around  its  circumference,  like  the 
boards  of  a  paddle-wheel.  Upon  these 
vanes  steam  is  propelled  from  a  close 
vessel;  a  rotatory  motion  is  thus  pro- 
duced, and  communicated  to  appropriate 
machinery. 

BRA'NCHIA  {/3P,'nXta).  Gills,  or 
respiratory  organs  which  extract  the 
oxygen  from  air  contained  in  water. 

BRANCHIO'PODA  (/3p«tx«*»  giUs. 
7roi/9,  7ro36r,  a  foot).  A  designation  of 
those  Crustacea  which  have  the  branchiae 
attached  to  numerous  pairs  of  similar 
feet.  They  possess  mandibles  and  max- 
illae, and  are  generally  small,  monoculous 
or  binoculous  animals,  with  a  large  cara- 
pace enveloping  the  whole  body. 

BRANCHIO'STEGI  (/3pdyXla,  gills, 
areata,  to  cover).  A  tribe  of  cartila- 
ginous fishes,  in  which  the  gills  are  free 
61 


and  covered  by  a  membrane,  as  in  the 
sturgeon. 

BRAND  or  BURN.  A  disease  in 
plants  by  which  their  leaves  and  tender 
bark  are  partially  destroyed,  as  if  they 
had  been  burned. 

BRASQUE.  A  term  used  by  the 
French  metallurgists  to  denote  the  lining 
of  a  crucible  or  a  furnace  with  charcoal. 

BRASS.  An  alloy  consisting  of  three 
parts  of  copper  and  one  of  zinc. 

BRAZIL  CURRENT.  A  branch  of 
the  great  Equatorial  Current,  separating 
from  the  equatorial  at  8°  S.  lat.,  opposite 
Cape  St.  Augustin,  running  to  the  south- 
west along  the  shores  of  Brazil  to  the 
mouth  of  the  Plata  river,  and  traced  to 
the  Straits  of  Magalhaens  and  Le  Maire. 
See  Guiana  Current. 

BRAZIL  WOOD.  The  wood  of  the 
Ccesalpinia  Braziliensis,  which  yields  a 
red  colouring  matter  used  by  dyers. 

BRAZILETTO.  An  inferior  species 
of  Brazil  wood,  brought  from  Jamaica. 
It  is  one  of  the  cheapest  and  least  es- 
teemed of  the  red-dye  woods. 

BRE'CCIA.  An  Italian  term  signify- 
ing an  opening  or  breaking  in  any  sub- 
stance, applied  by  mineralogists  to  those 
compound  stones  which  consist  of  agglu- 
tinated fragments  of  considerable  size. 
When  the  agglutinated  parts  are  rounded, 
the  stone  is  called  pudding-stone.  Ac- 
cording to  the  nature  of  their  component 
parts,  breccias  are  called  calcareous,  sili- 
cious,  &c. 

BREEZE,  SEA  and  LAND.  Names 
given  to  winds  of  a  very  limited  range, 
experienced  on  the  coasts  of  tropical 
countries,  and  depending  on  local  cir- 
cumstances. 

1.  Sea  breeze.  From  its  low  conduct- 
ing power,  the  surface  of  the  land  is 
more  quickly  heated  than  the  sea,  so 
that  soon  after  sunrise  the  expanded  air 
over  the  former  begins  to  ascend,  and  is 
replaced  by  the  colder  air  from  the  sea, 
forming  the  sea  breeze. 

2.  Land  breeze.  After  sunset,  the 
earth's  heat,  being  diminished,  is  more 
quickly  dissipated  by  radiation  than  that 
of  the  sea, ,  and  the  air  over  the  land 
becomes  dense  and  flows  outwards,  dis- 
placing the  air  over  the  sea,  and  pro- 
ducing the  land  breeze. 

BRENTl'DES.  A  family  of  Coleo- 
pterous insects,  named  from  the  genus 
Brentus,  and  belong  to  the  section  Rhyn- 
cophora  and  sub-section  Recticornes. 

BRE'VIPENNES  (brevis,  short,  penna, 
a  quill).     Short-quilled;   a    designation 


BRU 


B  UL 


of  Cuvier's  first   family  of    the     order 
Grallcc,  of  which  the  ostrich  is  the  type. 

BRE'ZILIN.  The  colouring  matter  of 
Brazil  wood,  obtained  from  several  spe- 
cies of  Ccesalpinia. 

BRISTOL  STONES  or  DIAMONDS. 
Small  brilliant  crystals  of  quartz  found 
in  the  neighbourhood  of  Bristol. 

BRITISH  GUM.  This  is  starch  re- 
duced to  a  gum-like  state  by  great  heat, 
and  used  by  calico  printers. 

BRITTLENESS.  A  quality  of  certain 
bodies  by  which  they  admit  of  being 
easily  broken,  or  separated  into  irregular 
fragments. 

BRO'MAL.  A  colourless  oily  liquid, 
corresponding  with  chloral,  and  formed 
by  adding  bromine  to  alcohol. 

BROMATO'LOGY  {/3PS>na,  food,  X6- 
Yor,  a  description).  A  description  or 
treatise  of  food. 

BROMELIA'CE^.  The  Pine-apple 
tribe  of  Dicotyledonous  plants,  named 
from  the  genus  bromelia,  and  chiefly  in- 
teresting from  their  capability  of  existing 
in  a  hot  dry  air  without  contact  with  the 
earth.    See  Air  Plants. 

BRO'MINE  (/3P»/uo9,  a  stench).  A 
deep  red-coloured  fetid  liquid,  formerly 
called  muride;  an  ingredient  of  sea- 
water,  of  several  salt  springs,  of  the 
ashes  of  sea-weeds,  and  of  those  of  the 
Janthina  violacca,  and  other  animals.  It 
combines  with  oxygen,  and  forms  bromic 
acid;  and  with  hydrogen,  forming  the 
hydrobromic. 

BRO'MURET.  A  combination  of  the 
bromic  acid  with  iodine,  phosphorus, 
sulphur,  &c. 

BRONZE.  An  alloy  of  copper,  8  or  10 
per  cent  of  tin  and  other  metals. 

BRO'NZITE.  A  variety  of  diallage, 
of  a  metallic  or  bronze  colour. 

BROWN  COAL.  An  imperfect  kind 
of  coal,  termed  also,  from  its  ligneous 
structure,  bituminous  wood. 

BROWN  SPAR.  Pearl  spar  or  sidero- 
calcite.  A  massive  mineral,  harder  than 
calcareous  spar,  but  yielding  to  the 
knife. 

BRU'CIA.  A  substance  procured  from 
the  bark  and  seeds  of  nux  vomica,  and 
from  St.  Ignatius's  bean.  It  is  said  to  be 
a  compound  of  strychnia  and  resin,  and 
not  a  peculiar  alkaloid. 

BRUNO'LIC  ACID.  One  of  the  par- 
ticular products  which  have  been  isolated 
in  the  distillation  of  coal. 

BRUNSWICK  GREEN.    An  ammo- 
niaco-muriate  of    copper,    used   for  oil 
painting. 
62 


BRYOZO'A  (fipvov,  moss,  £woi/,  an 
animal).  A  term  applied  by  Ehrenberg 
to  a  class  of  highly-organized  polyps, 
most  of  the  species  of  which  incrust 
other  animals  or  bodies  like  moss.  They 
have  been  recently  designated  by  Dr. 
Arthur  Farre,  ciliobrachiate  polyps.  They 
are  among  the  species  ranged  by  Cuvier 
under  the  head  of  tubular  polyps. 

BU'CCAL  {bucca,  the  mouth  or  cheeks). 
Belonging  to  the  mouth. 

BUCCINI'NJE.  Whelks ;  a  sub-family 
of  the  Muricidce,  named  from  the  genus 
buccinum,  and  including  shells  generally 
recognized  by  the  abrupt  termination  of 
the  base,  which  is  deeply  notched. 

BUCE'RIDjE.  The  Hornbills ;  a  fa- 
mily of  the  Insessores,  or  Perching-birds, 
readily  distinguished  by  the  enormous 
size  of  their  bills,  which  are  enlarged 
into  protuberances  resembling  horns. 
See  Conirostres. 

BUD,  LEAF,  and  FLOWER.  I.  A 
leaf-bud  (bourgeon)  is  a  young  plant 
produced  without  the  agency  of  sexes, 
and  consisting  of  rudimentary  leaves 
surrounding  a  growing  vital  point,  which 
elongates  upwards  in  the  form  of  stem, 
and  downwards  in  the  form  of  root. 
2.  A  flower-bud  (bouton)  consists  also  of 
rudimentary  leaves  surrounding  a  fixed 
vital  point,  which,  when  fully  developed, 
assumes  the  form  of  floral  envelopes,  or 
sexual  apparatus. 

BUFO'ID^E  {bufo,  a  toad).  The  Toad 
tribe ;  one  of  the  principal  divisions  of 
the  Anoural  order  of  Amphibious  ani- 
mals, which  undergo  a  metamorphosis 
similar  to  that  of  the  frogs,  but,  unlike 
these,  are  usually  found  at  a  distance 
from  water.     See  Rnnidce. 

BULB.  A  scaly  leaf-bud,  which  deve- 
lopes  roots  from  its  base,  and  a  stem  from 
its  centre.  When  the  outer  scales  are 
thin,  and  cohere  in  the  form  of  a  thin 
envelope,  as  in  the  onion,  this  is  the 
tunicated  bulb.  When  the  outer  scales 
are  distinct  and  fleshy,  as  in  the  lily,  this 
is  called  the  naked  bulb.  There  can  be  no 
such  thing  as  a  solid  bulb.    See  Cormus. 

BU'LBLET.  Bulbille.  A  bulb  which 
separates  spontaneously  from  the  stem 
of  a  plant,  as  in  lilium  bulbiferum. 

BULBOTU'BER.  A  short,  roundish, 
underground  stem,  resembling  a  bulb. 
The  term  was  applied  by  Ker  to  the 
Cormus. 

BU'LLAD^E.  A  family  of  marine 
mollusca,  belonging  to  the  fourth  order 
of  Cuvier's  Gasteropods,  and  named  from 
the  genus  bulla . 


C  AC 

BUPRE'STIDjE.  A  family  of  Coleo- 
pterous insects,  named  from  the  genus 
buprestis,  and  belonging  to  the  section 
Pentamera  and  sub-section  Sternoxi  of 
Latreille. 

BURE'TTE.  A  French  term  applied 
to  a  chemical  instrument  for  dividing  a 
given  portion  of  liquid  into  100  or  1000 
equal  parts. 

BURNING-GLASS.  A  glass  lens 
which  refracts  the  rays  of  the  sun  into  a 
focus.  The  solar  rays  may  also  be  brought 
to  a  focus  by  reflection  from  a  concave 
mirror,  which  is  then  called  a  burning 
mirror. 

BURNT- EAR.  A  disease  in  corn,  in 
which  the  fructification  of  the  plant  is 
destroyed,  and,  as  it  were,  burned  up. 
By  the  French  it  is  called  charbon,  by 
the  Germans  brand.  The  disease  is  pro- 
duced, according  to  De  Candolle,  by  a 
minute  fungus,  termed  uredo  carbo, 
which  he  distinguishes  from  the  uredo 
caries,  or  the  cause  of  smut. 

BUTOMA'CEiE.  A  natural  order  of 
Monocotyledonous  plants,  named  from 
the  butomus  umbellatus.  They  are  tri- 
petaloideous,  with  several  carpels,  the 
entire  lining  of  which  is  covered  with 
seeds. 

BUTTERS.  A  term  formerly  applied, 
in  Pharmacy,  to  butter-like  substances, 
as  those  of  antimony,  of  bismuth,  &c, 
meaning  the  chlorides  of  those  metals. 
Precipitated  sulphur  was  also  called 
butter  of  sulphur.     Vegetable  butters  is  a 


CAD 

term  also  applied  to  the  concrete  oil  of 
certain  plants,  from  its  resemblance  to 
butter  produced  from  the  milk  of 
animals. 

BUTTON.  A  technical  term  applied 
to  the  round  mass  of  metal  found  at  the 
bottom  of  the  crucible  after  fusion,  or  in 
the  cupel  in  the  process  of  assaying. 

BU'TYRIC  ACID  {butyrum,  butter). 
An  oily  limpid  liquid  ;  one  of  the  volatile 
acids  of  butter.  By  distillation  it  yields 
a  substance  called  butyrone. 

BU'TYRINE  {butyrum,  butter).  A 
peculiar  oleaginous  matter,  found  in  but- 
ter, combined  with  oleine  and  stearine, 
and  a  small  quantity  of  butyric  acid. 

BYSSI'FERA  (byssus,  and  fero,  to 
bear).  A  family  of  acephalous  mollusca, 
which  are  attached  to  foreign  bodies  by 
means  of  a  byssus. 

BY'SSOLITE  (/3vacof,  byssus,  \l0ot,  a 
stone).  A  massive  filamentous  mineral, 
implanted  like  moss  on  certain  stones,  at 
the  foot  of  Mont  Blanc,  and  also  near 
Oisans,  on  gneiss. 

BY'SSUS  (/3uo-«ro9,  fine  flax).  A  term 
applied  to  the  silky  filaments  which  pro- 
ject from  the  bivalve  called  Pinna,  and 
hence  applied  to  the  analogous  parts  in 
other  molluscous  animals.  In  Crypto- 
gamic  botany,  the  term  byssus  has  been 
given  to  all  those  filamentous  plants 
which  inhabit  cellars  and  subterranean 
abodes,  and  are  now  ascertained  to  con- 
sist of  fungaceous  plants  in  an  early 
state  of  growth. 


CA'CHOLONG.  A  variety  of  quartz 
found  on  the  borders  of  the  river  Cach, 
in  Bucharia.  In  the  Calmuc  language, 
cholong  is  said  to  signify  a  stone. 

CACODY'L  (icaKtodn?,  fetid).  A  limpid 
liquid,  supposed  by  Berzelius  to  be  the 
compound  radical  of  a  series  of  arsenical 
compounds,  and  named  in  reference  to 
the  repulsive  odour  of  its  oxide,  alcarsin. 
Cacodylic  acid  is  obtained  by  the  oxida- 
tion of  cacodyl  and  its  oxide,  and  is  syn- 
onymous with  alcargen. 

CACTA'CEjE.  The  Indian-Fig  tribe 
of  Dicotyledonous  plants.  Succulent 
shrubs,  usually  without  leaves  and  with 
spinous  buds.  Sepals  and  petals  con- 
founded ;  stamens  indefinite ;  ovary  in- 
ferior, 1 -celled;  fruit  succulent,  eaten 
63 


under  the  name  of  Indian  figs.  All  the 
species  are  considered  to  be  American. 

CA'DENCE  {cado,  to  fall).  The  close 
of  a  passage  in  music,  or  the  resolution 
of  a  dissonant  into  a  consonant  chord. 
Also,  an  extemporaneous  addition  made 
by  the  performer  at  the  end  of  a  piece  of 
music. 

The  perfect  cadence  is  composed  of  the 
chord  of  the  dominant,  or  of  the  domi- 
nant seventh,  followed  by  that  of  the 
tonic.  The  imperfect  cadence  consists  of 
the  chord  of  the  tonic,  followed  by  that 
of  the  dominant,  but  rarely  occurs  as  a 
final  close.  The  interrupted  or  deceptive 
cadence  is  formed  by  a  chord  quite  foreign 
to  that  which  was  expected,  thus  evading 
the   close,    and    deceiving   expectation. 


C  AL 


C  AL 


The  plagal  cadence,  sometimes  called  an 
imperfect  cadence,  consists  of  the  chord 
of  the  subdominant,  followed  by  that  of 
the  tonic. 

CADET,  LIQUOR  OF.  Alcarsin. 
A  liquid  obtained  by  distilling  acetate  of 
potash  and  arsenious  acid,  and  remark- 
able for  its  insupportable  odour  and 
spontaneous  inflammability  in  air. 

CA'DMIUM.  A  bluish-white  metal 
found  in  several  of  the  ores  of  zinc ;  so 
named  from  cadmia  fossilis,  a  former 
name  of  the  common  ore  of  zinc. 

CADU'CIBRA'NCHIATE  {caducus, 
falling,  branchice,  gills).  A  division  of 
Amphibious  animals,  which,  though  fur- 
nished in  the  early  period  of  their  exist- 
ence with  gills  and  lungs,  eventually  lose 
all  traces  of  the  former,  as  in  the  frog, 
the  newt,  &c. 

CADU'COUS  {cado,  to  fall).  A  term 
applied  in  Botany  to  parts  which  fall 
early,  as  the  calyx  of  the  poppy,  the 
petals  of  the  gum  cistus,  &c.  Parts  which 
continue  on  the  plant  long  are  termed 
persistent. 

CiE'CUM  {ccecus,  blind).  A  blind  tube, 
or  cul-de-sac;  a  tube  which  terminates 
in  a  closed  end. 

CiE'SPITOSE  {ccespes,  a  turf  or  sod). 
Growing  in  tufts ;  forming  dense  patches 
or  tufts,  as  the  young  stems  of  many 
plants. 

CjESU'RA  {ccedo,  to  cut).  A  term  de- 
noting a  cutting,  equivalent  to  the  Greek 
roixrj,  and  applied  by  grammarians  to  the 
place  in  a  verse  where  a  word  ends,  and 
the  voice  pauses  a  little.  1.  In  a  heroic 
or  hexameter,  the  most  common  caesura 
is  the  penthemimeral,  which  occurs  after 
the  fifth  foot,  as,  "  Tityre,  tu  patulae," 
&c.  2.  The  hepht/i  emimeral  caesura  oc- 
curs after  the  seventh  half-foot,  as  "  For- 
mosam  resonare  doces,"  &c.  3.  The 
bucolic  caesura,  used  by  the  bucolic  or 
pastoral  poets,  occurs  after  the  fourth 
dactyl,  as,  "  Ambo  florentes  aetatibus," 
&c.  4.  The  caesura  occurs  also  after  the 
third  trochee,  after  the  second  dactyl,  and 
after  the  third  dactyl,  the  last  instance 
being  somewhat  rare.     See  Incision. 

CA'FFEIC  ACID.  An  acid  discovered 
in  coffee,  containing  the  aroma  of  the 
roasted  seed.  Caffein  is  a  neutral  crys- 
talline substance  obtained  from  unroasted 
coffee. 

CAIRNGORM.  A  species  of  quartz, 
so  named  from  a  mountain  of  that  name 
in  Scotland,  where  it  was  once  plentiful. 
It  is  a  variety  of  rock  crystal. 

CA'LAMINE  {calamus,  a  reed).  The 
64 


impure  carbonate  of  zinc;  a  pulveru- 
lent mineral,  generally  of  a  reddish 
colour. 

CA'LAMITE.  A  light-green  mineral 
found  in  serpentine  with  magnetic  iron 
and  calcareous  spar,  near  Normark  in 
Sweden. 

CA'LAMUS.  A  reed  ;  a  term  adopted 
by  De  Candolle  for  all  fistular  simple 
stems  without  articulations,  as  those  of 
rushes. 

CA'LATHIS;  CALA'THIUM  {nd\a- 
6ts,  KaXdOtov,  a  basket).  Terms  adopted 
by  some  continental  botanists  for  the 
capitulum  or  anthodium  of  other  writers, 
denoting  the  inflorescence  of  Composite. 

CALC  SINTER  (kalk,  lime,  sintern, 
to  drop).  A  German  name  for  carbonate 
of  lime,  occurring  in  stalactitical  forms 
by  the  infiltration  of  carbonated  lime- 
water  through  the  crevices  of  the  roofs  of 
caverns. 

CALCAIRE  GROSSIER.  Coarse  lime- 
stone; an  extensive  stratum,  or  rather, 
series  of  strata,  found  in  the  Paris- 
Basin,  belonging  to  the  Eocene  tertiary 
period. 

CA'LCARATE  {calcar,  a  spur). 
Spurred,  having  a  spur  or  spur-like  ap- 
pendage, as  the  petals  of  aquilegia.  The 
calcar  is  sometimes  called  nectarotheca, 
or  honey-depository,  though  it  rarely 
secretes  honey. 

CALCA'REOUS.  The  name  of  a  class 
of  earths,  consisting  of  lime  and  carbonic 
acid,  as  chalk,  marble,  &c.  1.  Calcareous 
rock  is  another  term  for  limestone.  2.  Cal- 
careous spar  is  crystallized  carbonate  of 
lime ;  Iceland  spar  is  one  of  its  purest 
varieties.  3.  Calcareous  grit  is  a  sub- 
division of  the  middle  oolitic  forma- 
tion. 4.  Calcareous  sandstone  is  another 
subdivision  of  the  same  formation. 

CA'LCES.  Plural  of  calx,  quicklime. 
A  former  name  for  oxides,  from  their 
earthy  character,  resembling  lime.  The 
calx  of  tin  is  now  called  the  oxide  of 
tin. 

CALCINATION  {calx,  quicklime). 
A  term  formerly  applied  to  express  the 
oxidation  of  a  metal  effected  by  the  action 
of  the  air :  the  oxide  thus  formed  was 
denominated  a  calx,  from  its  being  earthy 
like  lime.  The  term  is  now  generally 
applied  whenever  any  solid  matter  has 
been  subjected  to  heat,  so  as  to  be  con- 
vertible into  a  state  of  powder. 

CA'LCIUM  {calx,  quicklime).  A  pe- 
culiar metal  discovered  by  Davy,  of 
which  lime  is  the  well-known  oxide. 

CALCTUFF.     An  alluvial  formation 


C  AL 


C  AL 


of  carbonate  of  lime,  probably  deposited 
from  calcareous  springs. 

CA'LCULUS.  The  Latin  term  for  a 
pebble,  used  in  former  times  for  the  pur- 
pose of  calculation.  Hence  it  is  applied 
to  any  branch  of  mathematics  which  in- 
volves calculation ;  any,  in  fact,  except 
pure  geometry.  The  several  branches 
are  noticed  under  their  specific  names. 

CA'LENDAR  (/ca\<?<o,  to  call).  Ka- 
lendar.  A  table  of  the  days  of  the  year, 
arranged  to  assist  the  distribution  of 
time,  and  to  indicate  remarkable  days 
connected  with  devotion  or  business. 
The  term  is  derived  from  the  Roman 
Calends,  or  the  first  day  of  the  month, 
when  the  pontiffs  called  the  people  to- 
gether, to  apprise  them  of  the  days  of 
festival  in  that  month. 

1.  Roman  Calendar.  In  the  Roman 
Calendar,  as  said  to  have  been  introduced 
by  Romulus,  the  year  was  divided  into 
10  months  only,  comprising  altogether 
304  days.  The  year  of  Romulus  was, 
therefore,  of  50  days'  less  duration  than 
the  lunar  year,  and  of  61  days'  less  than 
the  solar  year;  and  its  commencement 
of  course  did  not  correspond  with  any 
fixed  season.  Numa  Pompilius  corrected 
this  calendar,  by  adding  two  months, 
Januarius  and  Februarius,  which  he 
placed  before  Mars, 

2.  Julian  Calendar.  In  order  to  render 
the  calendar  still  more  correct,  Julius 
Caesar  fixed  the  solar  year  at  365  days, 
6  hours,  comprising,  as  was  supposed, 
the  period  from  one  vernal  equinox  to 
another.  The  six  hours  were  set  aside, 
and,  at  the  end  of  four  years,  forming  a 
day,  the  fourth  year  was  made  to  consist 
of  366  days.  The  day  thus  added  was 
called  intercalary.     See  Bissextile. 

3.  Gregorian  Calendar.  The  Julian 
Calendar  was  defective  in  this  particular 
— that  the  solar  year,  consisting  of  365 
days,  5  hours,  and  49  minutes,  and  not 
of  365  days,  6  hours,  there  was  a  dif- 
ference, between  the  apparent  year  and 
the  real  year,  of  eleven  minutes.  This 
difference  having  amounted,  in  the  year 
1582,  to  ten  entire  days,  Gregory  XIII. 
ordained  that  the  5th  of  October  in  that 
year  should  be  counted  as  the  15th,  thus 
cutting  off  ten  days  from  that  year ;  and 
to  prevent  the  recurrence  of  this  error,  it 
was  further  determined  that  the  year 
beginning  a  century  should  not  be  bis- 
sextile, with  the  exception  of  that  begin- 
ning each  fourth  century.  This  is  the 
Gregorian  or  New  Style,  as  distinguished 
from  the  Julian  or  Old  Style. 

65 


CALFBRE.  A  French  term,  signifying 
the  bore  of  a  cannon,  and  generally  ex- 
pressive of  the  diameter  of  any  round 
substance,  and,  figuratively,  of  the  mental 
capacities.  The  calibre  of  round  bodies 
is  measured  by  what  are  called  Callipers, 
or  calliper  compasses,  which  are  formed 
with  curved  legs,  furnished  with  knobs 
instead  of  points. 

CA'LICO-PRINTING.  The  art  of 
dyeing  cotton  cloth,  called  calico  from 
Calicut  in  India,  with  one  or  more  colours, 
in  certain  parts,  leaving  the  rest  of  the 
material  in  its  original  state. 

CALFPPIC  PERIOD.  In  ancient 
chronology,  a  correction  of  the  Metonic 
cycle  of  nineteen  solar  years,  proposed 
by  Calippus.  At  the  end  of  four  of  these 
cycles,  there  is  an  excess  of  one  day  and 
six  hours  over  the  number  of  lunations. 
Calippus,  therefore,  proposed  to  quadruple 
the  Metonic  period,  and  deduct  a  day 
from  the  end  of  it  by  reducing  the  days 
of  one  of  the  months  from  30  to  29. 

CALLUS,  or  CALLOSITY.  A  term 
applied  to  the  thickening  of  enamel  upon 
a  shell,  resembling  a  tumour,  as  in  the 
inner  lip  of  the  olives,  and  near  the 
hinge  of  some  bivalves. 

CALO'RIC  (calor,  heat).  An  ima- 
ginary fluid,  or  condition  diffused  through 
all  bodies.  In  chemical  language,  caloric 
is,  properly,  the  matter  producing  the 
sensation  of  heat.  The  words,  however, 
are  often  confounded,  the  term  heat  being 
employed  for  both  the  cause  and  the 
effect. 

1.  Sensible  or  free  caloric  is  that  which 
produces  the  sensation  of  heat,  or  affects 
the  thermometer.  Insensible  or  latent 
caloric  is  that  portion  which  passes  into 
bodies  during  a  change  of  form,  without 
elevating  their  temperature ;  as  into  ice 
at  32°,  as  it  becomes  water,  and  termed 
caloric  of  fluidity ;  or  into  water  at  212°, 
as  it  passes  into  vapour,  and  termed 
caloric  of  vaporization. 

2.  Specific  caloric  is  the  relative  pro- 
portion of  caloric  which  any  body  retains 
without  the  effects  being  sensible;  and 
the  power  of  retention  which  a  body  pos- 
sesses, is  called  its  capacity  for  caloric. 
The  specific  caloric  of  water  is  23  times 
as  great  as  that  of  mercury;  thus,  if 
equal  weights  of  the  former  at  40°,  and 
of  the  latter  at  160°,  be  mixed  together, 
the  resulting  temperature  is  45°. 

CALORFFIC  RAYS.  Those  rays 
proceeding  from  the  sun  or  any  burning 
body,  which  impart  the  sensation  and 
other  effects  of  heat. 


CAM 


CAM 


CALORI'METER  (calor,  heat,  Mt'Tpov, 
measure).  An  apparatus  for  measuring 
the  capacity  of  bodies  for  heat  by  the 
quantity  of  ice  which  they  are  capable  of 
melting.  Rumford's  water  calorimeter, 
consisting  of  a  vessel  filled  with  water 
through  which  a  spiral  tube  is  conducted, 
is  employed  for  ascertaining  the  specific 
heat  of  gases. 

CALOfRIMOTOR,  (calor,  caloric, 
moveo,  to  move).  An  apparatus,  con- 
structed by  Dr.  Hare  of  Philadelphia,  for 
evolving  caloric. 

CALY'BIO  {kcl\v/3iov,  a  little  hut).  A 
term  by  which  Mirbel  designates  the 
fruit  called  gland  or  nucule  by  other 
writers.  It  is  applied  to  the  fruit  of  the 
oak,  of  the  chestnut,  of  the  hazel. 

CALYCIFLO'RiE  (calyx,  a  flower-cup, 
flos,  a  flower).  Plants  which  have  their 
flowers  furnished  with  both  a  calyx  and 
a  corolla,  the  latter  consisting  of  distinct 
petals,  and  their  stamens  perigynous. 

CALY'CULATE  (calyculus,  a  little 
calyx).  Having  an  involucrum  of  bracts 
exterior  to  the  calyx,  as  in  many  of  the 
compositae. 

CALY'PTRA  (Ka\«'/7TT&),  to  veil).  Lite- 
rally, a  veil  or  hood.  A  term  applied  to 
a  membranous  covering,  which  envelopes 
parts  of  certain  plants,  as  the  spore- 
vessel  of  mosses,  the  stamens  of  euca- 
lyptus, &c.  Such  parts  are  said  to  be  ca- 
lyptrate. 

CALYPTR.E'ID,E.  Chambered  lim- 
pets ;  a  family  of  gasteropods,  named 
from  the  genus  Calyplrcea.  Some  of 
these  occur  in  a  fossil  state  in  beds  of  the 
pliocene,  miocene,  and  eocene  periods. 

CALYX  (fcdAuf,  a  cup).  The  flower- 
cup,  or  external  envelope  of  the  floral 
apparatus.     See  Sepal. 

CA'M  BIUM.  A  viscid  juice  abounding 
in  spring  between  the  bark  and  wood  of 
trees,  and  supposed  to  be  closely  con- 
nected with  the  developement  of  woody 
fibre. 

CA'MBRIAN  GROUP.  A  Welsh 
group  of  rocks,  constituting  the  upper 
of  the  clay-slate  series,  and  comprising 
the  Snowdon  Rock,  the  Bala  Limestone, 
and  the  Plinlimmon  Rocks. 

CAME'LIDjE.  The  Camel  tribe;  a 
family  of  the  Ruminantia,  including  the 
camels  of  the  Old  World,  and  the  lamas 
of  the  New.  By  some  naturalists  they 
are  referred  to  the  horse  tribe  of  the 
Pachydermata. 

CAM E'LO PARDEE.  A  family  of  the 
Ruminantia,  including  only  the  giraffes, 
and  characterized  by  the  shortness  and 


permanence  of  the  horns,  which  are  co- 
vered by  a  skin. 

CAME'LOPA'RDALUS.  The  Ca- 
mel o,. aid  ;  a  modern  northern  constel- 
lation, consisting  of  fifty -eight  stars. 

CA'MERA  OBSCURA.  An  instru- 
ment consisting,  as  the  term  denotes,  of 
a  darkened  chamber,  into  which  the  rays 
of  light,  from  an  illuminated  object,  are 
admitted  by  means  of  a  small  aperture  ; 
these  rays  are  received  upon  a  white 
screen,  and  thus  the  object  is  distinctly 
seen  in  an  inverted  position.  The  in- 
strument is  constructed  on  the  principle 
that  light  is  propagated  in  right  lines. 

Camera  lucida.  This  term  denotes  a 
lightened  chamber,  though  no  chamber  is 
employed.  The  contrixance  is  founded 
on  the  fact,  that  when  light  is  attempted 
to  be  thrown  from  a  denser  into  a  rarer 
medium  at  more  than  a  certain  angle, 
depending  on  the  two  media,  no  light 
will  pass  through,  but  all  will  be  reflected. 
The  principle  is  the  same  as  that  of  the 
camera  obscura,  viz.  that  of  throwing 
images  of  external  objects  upon  a  plane 
or  curved  surface,  for  the  purpose  of 
drawing  or  amusement. 

CAMPANULA'CEtE  (campanula,  a 
little  bell).  The  Campanula  tribe  of 
Dicotyledonous  plants.  Herbaceous 
plants  or  under-shrubs,  yielding  a  milky 
juice.  Corolla  gamopetalous,  inserted 
into  the  top  of  the  calyx,  and  withering 
on  the  fruit.  Stamens  inserted  into  the 
calyx,  alternate  with  the  lobes  of  the 
corolla.  Ovary  inferior,  with  two  or 
more  cells.  Fruit  dry,  crowned  by  the 
withered  calyx  and  corolla,  and  dehiscing 
by  apertures  or  valves. 

CAMPA'NULATE  (campanula,  a  little 
bell).  Bell-shaped ;  a  term  applied  in 
Botany  to  the  calyx  and  the  corolla,  when 
shaped  like  a  little  bell. 

CA'MPHINE.  A  spirit  for  burning 
in  lamps,  said  to  consist  of  oil  of  turpen- 
tine with  a  species  of  naphtha. 

CA'MPHOGEN.  A  colourless  liquid 
procured  by  distilling  camphor  with  an- 
hydrous phosphoric  acid. 

CA'MPHORIC  ACID.  An  acid  pro- 
cured by  digesting  camphor  in  nitric  acid, 
Campholic  acid  has  the  consistence  of 
camphor,  but  contains  two  parts  more  of 
hydrogen  and  oxygen. 

CA'MPHRONE.  A  light  oil  procured 
by  placing  Camphor  in  contact  with  red- 
hot  quicklime. 

CAMPYLO'TROPOUS  Oaju^Xor, 
curved,  Tpen-w,  to  turn).  A  term  applied 
to  the  ovule  of  plants,  when  its  axis,  in- 


CAN 


CAP 


stead  of  remaining  rectilinear,  is  curved 
down  upon  itself,  the  base  of  the  nucleus 
still  continuing  to  be  contiguous  to  the 
hilum. 

CAMWOOD.  A  red  dye-wood,  prin- 
cipally obtained  from  Sierra  Leone,  and 
used  with  alum  and  tartar  as  a  mordaunt. 

CANAL.  A  groove  observed  in  dif- 
ferent parts  of  certain  spiral  shells,  be- 
longing to  the  Zoophaga,  or  carnivorous 
tribe,  and  adapted  for  the  protrusion  of 
the  long  cylindrical  siphon  possessed  by 
these  animals.  This  part,  also,  consti- 
tutes the  base  of  the  shell. 

Besides  this  there  is,  in  many  of  the 
mitres,  strombi,  and  other  predaceous 
genera,  another  canal  or  groove,  placed 
in  the  interior  of  the  upper  part  of  the 
aperture,  the  use  of  which  has  not  been 
ascertained. 

CANALI'CULATE  {canaliculus,  a  little 
canal).  Channelled  ;  long  and  concave,  as 
the  leaves  of  tradescantia. 

CANCE'LLATE  (cancelli,  lattice- 
work). Latticed ;  any  thing  which  is 
cross-barred,  or  marked  by  lines  which 
cross  each  other  at  right  angles ;  the  cha- 
racter of  a  leaf  which  has  veins  without 
connecting  parenchyma,  anastomosing 
and  forming  a  kind  of  net-work,  as  in 
hydrogeton  fenestralis. 

CA'NCER.  The  Crab ;  the  fourth  of 
the  zodiacal  constellations,  consisting  of 
83  stars.  It  denotes  the  first  month  of 
winter,  extending  from  the  20th  of  De- 
cember to  the  20th  of  January,  and  bears 
allusion  to  the  retrograde  motion  of  the 
sun  at  the  winter  solstice. 

CANES  VENA'TICI.  Asterion  and 
Chara,  the  Greyhounds ;  a  modern  north- 
ern constellation,  consisting  of  twenty- 
five  stars. 

CANI'CULAR  PERIOD  (canicula, 
the  dog-star).  A  period  of  forty  days, 
comprising,  according  to  the  old  calen- 
dars, twenty  before  and  twenty  after  the 
heliacal  rising  of  the  Canicula,  Sirius,  or 
dog-star.  The  time  of  the  heliacal  rising 
of  the  dog-star,  however,  varies  in  con- 
sequence of  the  precession  of  the  equi- 
noxes, so  that,  instead  of  happening  in 
the  warmest  season,  it  has  gradually  ad- 
vanced towards  the  autumn.  In  modern 
almanacs,  therefore,  the  period  of  the 
rising  of  the  star  has  been  disregarded, 
and  the  canicular  days  are  reckoned  as 
commencing  on  the  third  of  July,  and 
ending  on  the  eleventh  of  August. 

CA'NID^  (canis,  a  dog).  The  Dog 
tribe ;  a  family  of  carnivorous  Vertebrata, 
which,  like  the  felidae,  are  digitigrade, 
67 


but  have  no  retractile  claws,  and  they 
are  further  characterized  by  the  presence 
of  two  flat  tuberculated  molar  teeth  be- 
hind the  great  incisor. 

CANIS  MAJOR.  The  Greater  Dog ; 
a  southern  constellation,  consisting  of 
thirty-one  stars,  the  principal  of  which  is 
Sirius. 

Canis  Minor.  The  Lesser  Dog ;  a 
southern  constellation,  consisting  of  four- 
teen stars,  the  principal  of  which  is 
Procyon. 

CANNEL  COAL.  A  bituminous  sub- 
stance, which  yields,  on  combustion,  a 
bright  flame  without  smoke.  The  term 
is  probably  a  vulgarism  for  candle  coal, 
in  allusion  to  its  illuminating  properties. 
It  occurs  in  most  of  the  English  collieries, 
especially  at  Wigan  in  Lancashire. 

CANNON  METAL.  An  alloy  of  cop- 
per, tin,  and  small  quantities  of  other 
metals,  used  for  casting  cannon. 

CANO'PUS.  A  star  of  the  first  mag- 
nitude, in  the  rudder  of  the  southern 
constellation  Argo. 

CANTATRICES  (canto,  to  sing). 
Songsters  ;  an  order  of  Birds,  so  named 
by  Macgillivray  on  account  of  their  being 
pre-eminently  musical,  as  the  orioles, 
thrushes,  chanters,  &c.  They  are  all  of 
small  size,  with  the  bill  slender,  and 
adapted  for  seizing  insects,  worms,  or 
soft  fruits.  They  thus  differ  from  the 
Vagatrices,  which  have  the  bill  more 
elongated  and  stronger;  and  from  the 
Deglubitrices,  in  which  it  is  short,  stout, 
and  conical. 

CANTON'S  PHOSPHORUS.  A  sub- 
stance made  by  exposing  calcined  oyster- 
shells  and  sulphur  to  #  red  heat.  On 
exposure  to  light,  it  acquires  the  property 
of  shining  in  the  dark. 

CAOUTCHOUC.  India  Rubber.  An 
elastic  resin  or  dried  juice  of  certain  trees 
growing  in  South  America  and  the  East 
Indies.  Caoutchine  is  a  liquid  procured 
by  the  distillation  of  caoutchouc. 

CAPACITY  FOR  HEAT.  The  power 
which  a  body  possesses  of  retaining  a 
certain  proportion  of  latent  heat.  See 
Caloric,  Specific. 

CAPE  (caput,  a  head).  A  headland, 
or  projecting  portion  of  a  coast.  It  some- 
times terminates  in  an  acute  angle,  and 
is  then  called  a  point.  If  the  projecting 
portion  is  small  or  low,  the  affix  ness  is 
employed  in  England,  as  in  such  terms 
as  Dungeness;  and  in  Scotland  that  of 
mull,  as  the  mull  of  Galloway. 

CAPE'LLA  or  a  AURI'G^.  The  She- 
Goat,  a  star  of  the  first  magnitude  in  the 


CAP 


CAR 


body  of  the  goat,  which  Auriga  is  repre- 
sented as  carrying.  This  is  a  double 
star,  with  a  small  proper  motion. 

CAPILLAME'NTUM  {capillus,  a  hair). 
A  term  applied  by  some  botanical  writers 
to  the  filament,  or  that  part  of  the  stamen 
which  supports  the  anther. 

CAPILLARY  TUBE  {capillus,  a  hair). 
A  minute  hair-like  tube,  so  small  as  to  be 
less  than  the  twentieth  of  an  inch  in 
diameter  inside,  used  for  experiments  in 
illustrating  capillary  attraction.  See  At- 
traction, Capillary. 

CAPILLI'TIUM  (capillus,  a  hair).  Li- 
terally, the  hair  of  the  head ;  a  kind  of 
purse  or  net,  in  which  the  sporules  of 
some  fungi  are  retained,  as  in  trichia. 

CA'PITATE  {caput,  capitis,  the  head). 
A  term  applied  to  any  part  of  a  body 
which  is  terminated  by  a  knob,  like  the 
head  of  a  pin ;  or  to  certain  hairs  in 
plants  which  terminate  in  a  glandular 
enlargement. 

CAPI'TULUM  (dim.  of  caput,  a  head). 
A  little  head  ;  a  form  of  inflorescence,  in 
which  numerous  flowers  are  placed  on  a 
depressed  axis,  as  in  Compositae.  It  is 
also  termed  anthodium,  calathium,  &c. 

CA'PNOMOR  (Ka7rv6r,  smoke,  /xolpa, 
part).  A  colourless  transparent  liquid, 
found  among  the  products  of  the  distilla- 
tion of  wood.  Its  name  is  derived  from 
it3  being  one  of  the  ingredients  of  smoke. 

CAPPARIDA'CE^.  The  Caper  tribe 
of  Dicotyledonous  plants.  Herbaceous 
plants,  shrubs,  or  trees ;  leaves  alternate ; 
sepals  4,  petals  4,  cruciate  ;  stamens  defi- 
nite or  indefinite ;  ovary  stalked ;  fruit 
1-celled.  The  flower-buds  of  Capparis 
spinosa  are  the  Capers  of  shops. 

CA'PRIC  and  CAPRO'IC  ACIDS.  Vo- 
latile odoriferous  compounds,  yielded  by 
butter  on  its  conversion  into  soap. 

CAPRICO'RNUS.  The  Goat;  the 
tenth  of  the  zodiacal  constellations,  con- 
sisting of  fifty-one  stars.  The  first  month 
of  summer,  extending  from  the  20th  of 
June  to  about  the  20th  of  July.  Capri- 
corn opens  and  begins  the  year ;  he  is 
the  leader  of  the  celestial  animals,  as  on 
earth  he  is  the  leader  of  the  flock. 

CA'PRIDiE  {caper,  a  goat).  The  Goat 
tribe;  a  family  of  the  Ruminantia,  in 
which  the  horns  are  directed  upwards 
and  backwards,  and  their  bony  core  is 
partly  cellular.  It  includes  only  the 
goats  and  sheep. 

CAPRIFICA'TION     (caprificus,    the 

wild  fig-tree).    The  process  of  fertilizing 

the  fig,  as  practised  in  the  Levant.    At 

the  ripening  period,  branches  of  the  wild 

68 


fig  are  placed  upon  the  cultivated  plants ; 
an  insect,  the  cynips  psenes,  brought  with 
the  wild  plant,  pierces  the  fruit,  and  ac- 
celerates its  maturation. 

CA'PRIFOLIA'CEJE.  The  Honey- 
suckle tribe  of  Dicotyledonous  plants. 
Shrubs  or  herbaceous  plants  with  leaves 
opposite ;  flowers  corymbose,  monopeta- 
lous;  stamens  alternating  with  the  lobes 
of  the  corolla ;  ovarium  inferior,  many- 
celled  ;  fruit  indehiscent. 

CAPRI MU'LGIDjE  (caprimulgus,  the 
goat-sucker).  The  Goat-suckers;  a  fa- 
mily of  the  Insessores,  or  Perching  birds, 
remarkable  for  their  nocturnal  habits, 
light  and  rapid  flight,  and  great  activity 
(see  Fissirostres).  By  Macgillivray,  these 
birds  are  placed  in  a  group,  belonging  to 
an  order  which  he  names  Volitatrices,  or 
Gliders. 

CA'PSTAN.  A  modification  of  the 
wheel  and  axle,  used  on  board  of  ships. 
It  consists  of  an  axle  placed  upright, 
with  a  head  or  drum,  pierced  with  holes 
for  the  levers.  The  weight  is  drawn  by 
a  rope  passing  two  or  three  times  round 
the  axle,  to  prevent  its  slipping.  The 
capstan  is,  in  fact,  a  wheel  and  axle,  of 
which  the  wheel  turns  horizontally ;  when 
the  wheel  turns  vertically,  the  machine 
is  called  a  windlass. 

CA'PSULA  (dim.  of  capsa,  a  chest). 
A  capsule  or  little  chest ;  a  term  applied 
in  botany  to  a  dry,  superior  fruit,  dehis- 
cent by  valves,  and  always  proceeding 
from  a  compound  ovarium.  By  some 
writers,  the  term  capsella  is  applied  to 
the  same  kind  of  fruit,  if  small  and  one- 
seeded. 

CARA'BIDjE  {carabus,  a  beetle).  A 
family  of  the  pentamerous  Coleoptera, 
consisting  of  a  numerous  tribe  of  Beetles, 
characterized  by  the  presence  of  six  palpi, 
and  by  the  hooked  termination  of  their 
claws.  They  are  aquatic,  or  terrestrial ; 
most  of  them  are  carnivorous. 

CA'RADOC  SANDSTONE.  A  divi- 
sion of  the  Lower  Silurian  Rocks,  con- 
sisting of  red,  purple,  green,  and  white, 
micaceous,  sometimes  quartzose  grits, 
and  limestones,  2500  feet  thick,  contain- 
ing corals  and  mollusca. 

CARBAZO'TIC  ACID.  Nitro-picric 
acid.  An  acid  formed  by  the  action  of 
nitric  acid  on  indigo,  and  named  from 
the  terms  carbon  and  azote. 

CARBON  {carbo,  a  coal).  A  substance 
well  known  under  the  form  of  coal,  char- 
coal, lamp-black,  &c.  In  chemical  lan- 
guage, it  denotes  the  pure  inflammable 
principle  of  charcoal ;  in  its  state  of  ab- 


CA  R 


CAR 


solute    purity,    it    constitutes    the    dia- 
mond. 

1.  Carbon  Vapour.  The  name  of  a  hypo- 
thetical substance,  for  carbon  has  never 
been  obtained  in  the  insulated  form  of 
vapour.  When  the  term  is  used  in  che- 
mical works,  it  denotes  the  condition  of 
carbon  as  it  exists  in  carbonfb  acid. 

2.  Carbon,  Animal.  Animal  charcoal, 
bone  charcoal,  and  ivory  black,  are  names 
applied  to  bones  calcined,  or  converted 
into  charcoal,  in  a  close  vessel. 

3.  Carbon,  Mineral.  A  term  applied 
to  charcoal,  with  various  proportions  of 
earth  and  iron,  without  bitumen.  It  has 
a  silky  lustre,  and  the  fibrous  texture  of 
wood.  It  occurs  stratified  with  various 
kinds  of  coal. 

4.  Carbonic  Acid.  A  pungent  and 
acidulous  gas,  often  issuing  naturally 
from  the  ground  in  volcanic  countries, 
and  produced  by  the  combustion  of  char- 
coal ia  oxygen  gas.  It  was  termed  by 
Black  fixed  air,  from  its  having  been 
found  to  exist,  in  a  fixed  state,  in  lime- 
stone. It  is  the  gas  produced  by  the 
vinous  fermentation. 

5.  Carbonates.  Compounds  of  carbonic 
acid  with  the  salifiable  bases.  They  are 
composed  either  of  one  atom  of  acid  and 
one  of  the  base,  or  of  two  of  acid  and  one 
of  the  base ;  the  former  are  called  car- 
bonates, the  latter  bi-carbonates. 

6.  Carboniferous.  A  term  usually  ap- 
plied, in  a  technical  sense,  to  an  ancient 
group  of  secondary  strata.  But  any  bed 
containing  coal  may  be  termed  carbonife- 
rous.    See  Coal  Formation. 

7.  Carbonization  The  union  of  carbon 
and  iron.  To  decarbonize  cast-iron  or 
steel,  is  to  drive  off  its  carbon  in  the  form 
of  carbonic  acid  gas. 

8.  Carburets.  Combinations  of  carbon 
with  some  metals  by  fusion  :  thus,  steel 
is  a  carburet  of  iron.  The  term  has  also 
been  applied  to  a  peculiar  compound  of 
sulphur  and  hydrogen,  the  carburet  of 
sulphur,  also  termed  sulphuret  of  carbon, 
and  alcohol  of  sulphur. 

9.  Carburetted  Hydrogen.  A  colour- 
less inflammable  gas,  abundantly  formed 
in  nature  in  stagnant  pools,  wherever 
vegetables  are  undergoing  the  process  of 
putrefaction;  it  also  forms  the  greater 
part  of  the  gas  obtained  from  coal.  This 
gas  was  formerly  called  heavy  inflammable 
air.     See  defiant  Gas. 

CA'RBUNCLE.    A  precious    stone  of 

the  ruby  kind,  of  a  very  rich,   glowing, 

.  blood-red  colour.     Ure  says  it  is  probably 

the  alamandine,  a  variety  of  noble  garnet. 

69 


CA'RCERULE  {career,  a  prison).  Die- 
resilis.  A  term  applied  by  Mirbel  to  a 
species  of  compound  fruit,  which  is 
many-celled,  superior ;  the  cells  are  dry, 
indehiscent,  few-seeded,  and  cohere  by  a 
common  style  round  a  common  axis.  It 
occurs  in  the  tropaeolum,  the  mallow,  the 
lime,  &c.     See  Coenobio. 

CARDIA'CEiE.  The  Cockle  tribe ;  an 
order  of  the  conchiferous  Mollusca, 
named  from  the  genus  cardia;  in  these 
the  mantle  is  not  only  closed,  but  ex- 
tended at  the  respiratory  apertures  into 
tubes  of  greater  or  less  length.  The  foot 
is  very  strong. 

CA'RDINAL  (cardo,  a  hinge).  An 
epithet  implying  importance,  being  sug- 
gestive of  the  hinge  or  pivot,  on  which 
every  thing  else  depends.  Thus,  it  de- 
notes the  north,  south,  east,  and  west 
points  of  the  compass  ;  the  zodiacal  signs 
Aries,  Cancer,  Libra,  and  Capricorn,  &c. 

CARI'NA.  Literally,  a  keel,  and 
hence  applied  to  the  two  lower  petals  of 
a  papilionaceous  corolla,  which  cohere  by 
their  lower  margin  in  the  form  of  a  keel, 
to  the  glumes  of  grasses,  &c.  By  Link, 
the  combination  is  expressed  by  the  term 
scaphium. 

CA'RINTHINE.  A  sub-species  of  the 
mineral  augite,  found  in  Carinthia,  in  a 
bed  in  primitive  rock,  associated  with 
quartz,  Kyanite,  garnet,  and  zoisite. 

CARMIN  E.  A  beautiful  red  pigment, 
obtained  from  cochineal. 

CARNE'LIAN  {caro,  carnis,  flesh). 
A  variety  of  agate,  presenting  in  some 
cases  a  flesh  colour;  its  colour  is  uni- 
form ;  it  is  never  figured  or  striped,  like 
other  varieties  of  agate. 

CARNEOUS  or  CARNOSE  (carnosus, 
fleshy).  Of  a  fleshy  consistence,  as  ap- 
plied to  succulent  leaves,  &c. 

CARNI'VORA  {caro,  carnis,  flesh, 
voro,  to  devour).  A  group  of  mammi- 
ferous  animals,  constituting  the  typical 
order  of  that  great  division  of  the  class 
which  subsist  on  animal  food.  These 
are  the  carnassiers  of  Cuvier. 

CARNO'SA  {carnosus,  fleshy).  Fleshy 
animals,  an  order  of  polyps,  including 
the  sea-anemone,  &c. 

CARPEL  (Kapvrof,  fruit).  A  technical 
term,  applied  in  Botany  to  a  leaf  in  a 
particular  state  of  modification,  consti- 
tuting the  pistil.  The  blade  of  the  leaf 
forms  the  ovary ;  the  elongated  midrib, 
the  style ;  and  the  apex  of  the  midrib, 
the  stigma.  The  edge  of  the  carpel,  which 
corresponds  to  the  midrib  of  the  leaf, 
constitutes  the    dorsal   suture;  that   of 


CAS 


CAT 


the  united  margins,  the  ventral.  See 
Pistil. 

CARPO'LOGY  (KapTrof,  fruit,  X6709, 
description).  That  branch  of  botany 
which  treats  of  the  structure  of  fruits. 

CARTESIAN  DIVER.  A  well-known 
glass  figure,  constructed  so  as  to  float  in 
a  vessel  of  water  above  whose  level  a 
small  portion  of  air  is  confined  in  such  a 
manner  that  if  this  air  be  compressed, 
the  figure  will  immediately  descend,  and 
rise  again  to  the  surface,  when  the  pres- 
sure ceases  to  be  exerted. 

CARTE'SIAN  PHILOSOPHY.  A 
system  of  mystical  and  pantheistic  philo- 
sophy introduced  by  Rene  des  Cartes. 
According  to  him,  consciousness  is  the 
ground  of  all  knowledge,  and  constitutes 
the  essence  of  the  soul;  its  objects  or 
ideas  are  of  three  kinds — acquired,  com- 
pounded, and  innate.  All  physical  phe- 
nomena are  referred  to  vortices,  or  mo- 
tions of  matter,  excited  by  the  Author  of 
all  things.  Des  Cartes  was  born  in  1596, 
and  was  contemporary  with  Lord  Bacon. 

CA'RTHAMIN.  A  beautiful  red  pig- 
ment, also  called  carthamic  acid,  pro- 
cured from  the  flowers  of  the  Carthamus 
tinctorius  or  Bastard  Saffron,  and  used 
in  silk  dyeing. 

CARU'NCLE  (caruncula,  dim.  otcaro, 
flesh).  A  little  piece  of  flesh;  a  soft 
wart-like  eminence ;  an  irregular  protu- 
berance of  the  testa  about  the  umbilicus 
of  certain  seeds. 

CARYOPHYLLA'CEiE.  The  Chick- 
weed  tribe  of  Dicotyledonous  plants. 
Herbaceous  plants,  with  leaves  opposite, 
and  tumid  nodes;  flowers  polypetalous, 
symmetrical ;  stamens  definite ;  ovarium 
one-celled,  with  a  free  central  placenta, 
fruit  a  one-celled  capsule,  by  obliteration 
of  the  dissepiments. 

Caryophyllaceous  Corolla.  A  corolla, 
the  petals  of  which  have  long,  narrow, 
and  distant  claws,  as  distinguished  from 
the  alsinaceous  corolla,  in  which  the 
petals  are  short  and  distant. 

CARYO'PSIS  [acipvov,  a  nut,  6'^«p, 
likeness).  A  one-cetled,  one-seeded,  su- 
perior, dry,  indehiscent  fruit,  with  the 
integuments  of  the  seed  cohering  insepa- 
rably with  the  endocarp  ;  the  character- 
istic fruit  of  the  Graminaceae. 

CASE  {casus,  a  falling).  This  word  is 
used  by  grammarians,  in  its  strict  sense, 
to  signify  a  certain  "  variation  in  the 
writing  and  utterance  of  a  noun,  denoting 
the  relation  in  which  it  stands  to  some 
other  part  of  the  sentence."  But  it  is 
sometimes  used  to  denote  that  relation 
70 


itself,  whether  indicated  by  the  termina- 
tion, or  by  a  preposition,  or  by  its  collo- 
cation. Much  confusion  has  arisen  from 
this  ambiguity  of  the  term.     Whately. 

CASE-HARDENING.  The  process  of 
converting  the  external  part  of  iron  into 
a  coating  of  steel,  by  cementation  for  a 
limited  time. 

CA'SEIC  ACID  (caseus,  cheese).  An 
acid  extracted  from  cheese,  and  supposed 
to  contain  many  of  the  properties  of  this 
substance.  Casein  or  caseum  is  the  curd 
of  the  coagulable  portion  of  milk,  a  prin- 
ciple analogous  to  albumen.  Caseous 
oxide  is  another  name  for  aposepedine, 
a  substance  procured  by  the  putrefaction 
of  animal  matter. 

CASSI'DEOUS  (cassis,  a  helmet).  Hel- 
met-shaped ;  a  designation  of  the  irre- 
gular corolla  of  aconitum  and  other 
plants,  in  which  one  petal  is  very  large 
and  hooded,  or  helmet-shaped. 

CA'SSIN^E.  Helmet-shells;  a  sub- 
family of  the  Muricidce,  named  from  the 
typical  genus  cassis,  and  characterized 
by  their  large  and  often  gigantic  size. 

CAST  IRON.  A  very  variable  mix- 
ture of  reduced  substances,  of  which  the 
principal  is  iron  combined  with  carbon. 
The  fused  metal  is  run  into  channels 
formed  in  sand,  and  thus  cast  into  in- 
gots or  pigs.  White  cast  iron,  which  is 
the  most  definite  variety,  consists  of  four 
atoms  of  iron  and  one  atom  of  carbon. 

CASTOR  or  a  GEMINORUM.  A 
star  of  the  first  magnitude  in  the  head  of 
the  Twins,  being  the  nearer  of  the  two  to 
the  pole. 

CA'STORIDjE  (castor,  the  beaver). 
The  Beaver  tribe  ;  a  family  of  the  Ro- 
dentia,  comprising  the  beavers,  voles, 
lemmings,  &c,  and  containing  many 
genera  which  closely  resemble  the  rats. 

CAT'S  EYE.  A  mineral,  of  a  beautiful 
appearance,  brought  from  Ceylon.  Its 
colours  are  grey,  green,  brown,  red,  of 
various  shades.  From  a  peculiar  play  of 
light,  arising  from  white  fibres  inter- 
spersed, the  name  has  been  derived  :  the 
French  call  the  appearance  chatoyant. 

CA'TACLYSM  (KuTaKAixr/iof,  a  flood). 
A  term  applied  by  geologists  to  a  deluge 
or  inundation. 

CATALOGUE  OF  THE  STARS.  A 
table  of  the  fixed  stars,  arranged  accord- 
ing to  their  right  ascensions,  or  longi- 
tudes, with  their  declinations,  or  latitudes, 
together  with  their  annual  variations  and 
magnitudes. 

CATA'LYSIS  (aara,  downwards,  \va, 
to  loosen).     Decomposition  by  contact. 


C  A  U 


C  A  V 


A  body  in  which  the  catalytic  force  re- 
sides, resolves  others  into  new  com- 
pounds, merely  by  contact  with  them,  or 
by  an  action  of  presence,  as  it  has  been 
termed,  without  gaining  or  losing  any 
thing  itself.  The  body  which  determines 
changes  in  another  is  called  the  catalytic 
agent:  yeast  resolves  sugar,  by  contact, 
into  carbonic  acid  and  alcohol. 

CATEGOREMA'TIC  {KaTnyopnua,  a 
predicate).  A  logical  designation  of  a 
word  which  is  capable  of  being  employed 
by  itself  as  a  term  or  predicate  of  a  pro- 
position. Adverbs,  prepositions,  &c.,and 
also  nouns  in  any  other  case  besides  the 
nominative,  are  syncategorematic,  i.  e. 
can  only  form  part  of  a  term. 

CATEGO'RICAL  {aarnvoptKo?,  cate- 
gorical, as  opposed  to  hypothetical).  A 
logical  term,  applied  to  a  proposition, 
which  affirms  or  denies  a  predicate  of 
a  subject  absolutely,  and  without  any 
hypothesis.     See  Proposition. 

CATEGORIES  {naTnyopia,  a  head  of 
predicables).  Categories  or  predicaments 
are  certain  general  heads,  employed  by 
logicians,  to  one  or  more  of  which  every 
term  may  be  referred.  The  categories 
enumerated  by  Aristotle  are,  oiia-ia, 
•noaov,  iroluv,  wpop  ri,  wov,  ttotc,  KeioQat, 
exeiv,  woieiv,  wderxetvi  which  are  usually 
rendered  in  English  by  substance,  quan- 
tity, quality,  relation,  place,  time,  situa- 
tion, possession,  action,  suffering.  They 
may  all  be  ultimately  referred  to  the  two 
heads  of  substance  and  attribute,  or,  in 
the  language  of  some  logicians,  accident. 

CATE'NARY  {catena,  a  chain).  The 
curve  described  by  a  rope  or  chain  which 
hangs  when  supported  at  both  ends.  All 
catenaries  are  similar  curves. 

CATKIN.  The  vernacular  name  of 
a  mode  of  inflorescence,  termed  by  the 
old  writers  catulus,  iulus,  and  nucamen- 
tum.     See  Amentum. 

CATO'PTRICS  {kc'itotttpov,  a  mirror). 
That  branch  of  the  science  of  Optics 
which  treats  of  the  reflection  of  light. 
See  Optics. 

CAUCA'SIAN  RACE.  One  of  the  five 
principal  races  of  mankind,  to  which  the 
nations  of  Europe  and  some  of  the  west- 
ern Asiatics  belong.  In  this  class  the 
head  is  almost  round,  and  of  the  most 
symmetrical  shape ;  the  cheek-bones 
without  ariy  projection  ;  the  face  oval ; 
and  the  features  moderately  prominent. 

CAU'DATE    (cauda,    a    tail).       Tail- 
pointed  ;  excessively  acuminated,  so  that 
the  point  is  long  and  weak,  like  the  tail 
of  an  animal. 
71 


CAU'DEX.  The  trunk  of  a  tree.  In 
Botany,  the  stem,  or  ascending  axis  of 
growth,  is  termed  caudex  ascendens  ;  the 
root,  or  descending  axis,  caudex  de- 
scendens.  The  rhizome  of  Iridaceae  and 
epiphytous  Orchidaceae  is  often  called 
caudex  repens. 

CAU'LICULE  (cauliculus,  a  little 
stalk).  By  this  term  some  botanists  dis- 
tinguish the  neck  of  the  embryo  in  plants 
from  the  plumule  or  gemmule.  Mirbel 
comprises,  under  the  general  term  blas- 
tema, the  radicle,  the  plumule,  and  the 
caulicule.  The  term  cauliculi  is  also 
applied  to  those  small  stems,  which  pro- 
ceed from  buds  formed  at  the  neck  of  a 
plant,  without  the  previous  production 
of  a  leaf. 

CAU'LINE  (caulis,  a  stem).  Belong- 
ing to  the  stem,  as  applied  to  leaves 
which  grow  from  the  stem,  as  distin- 
guished from  radical  or  root  leaves. 

CAU'LIS.  The  Latin  term  for  a  stem, 
but  applied  in  botany  to  the  ascending 
caudex  of  herbaceous  plants  or  shrubs. 
In  trees,  the  main  stem  is  sometimes 
called  caulis  arboreus,  but  more  com- 
monly the  trunk.  The  caulis  excurrens 
is  a  stem  which  rises  vertically  from  the 
earth,  and  bears  branches  on  its  sides ; 
the  caulis  deliquescens,  a  stem  which  at  a 
certain  distance  from  the  earth  throws 
out  irregular  ramifications.  The  stem  of 
grasses  is  called  the  culmus  or  straw ;  that 
of  rushes,  the  calamus  or  reed.  Plants 
which  have  no  distinct  stem,  are  called 
acaulescent. 

CAULOCA'RPOUS  (Kau\6r,  a  stem, 
Kapno?,  fruit).  A  term  applied  in  bota- 
nical glossology  to  those  polycarpous 
plants,  whose  stem  endures  many  years, 
constantly  bearing  flowers  and  fruits;  as 
trees  and  shrubs.     See  Rhizocarpous. 

CAU'STIC  CURVE  (/caixm/co?,  burn- 
ing). In  transcendental  geometry,  a  curve 
to  which  the  rays  of  light,  reflected  or 
refracted  by  another  curve,  are  tangents. 
It  is  termed  caustic,  owing  to  the  accu- 
mulation of  heat  from  the  collection  of 
the  rays  of  light  along  the  curve.  Caustic 
curves  are  of  two  kinds  ;  catacaustics,  or 
those  formed  by  reflection,  and  dia- 
causlics,  or  those  formed  by  refraction. 

CAUSTI'CITY  {Kaita.  Kavau),  to  burn). 
That  property  of  certain  substances,  as 
the  pure  alkalis,  concentrated  acids,  and 
metallic  salts,  by  which  they  combine  so 
powerfully  with  organized  bodies  as  to 
destroy  their  texture. 

CA'VERNOUS  TEXTURE.  A  term 
applied,    in  geology,  to  that  texture  of 


CEM 


CEP 


aggregated  compound  rocks,  which  is  cha- 
racterized hy  the  presence  of  numerous 
small  cavities,  of  a  roundish,  oval,  or 
other  form,  as  in  lava. 

CA'VID^.  The  Guinea-pig  tribe;  a 
family  of  the  Rodentia,  containing  the 
largest-sized  animals  of  the  order,  indi- 
genous in  tropical  America,  where  they 
replace  the  hares  and  rabbits  of  cold 
climates) 

CAVTTA'RIA  {cavitas,  a  cavity).  In- 
testinal worms,  or  Entozoa,  which  have 
an  intestinal  canal  floating  in  a  distinct 
abdominal  cavity. 

CAWK.  A  technical  term  applied  to 
opaque  sulphate  of  baryta,  or  vitriolated 
heavy  spar. 

CE'BRIONITES.  A  family  of  Coleo- 
pterous insects,  of  the  section  Malaco- 
derma  of  Latreille,  named  from  the 
genus  cebrio. 

CE'DRIRET.  A  substance  'found 
among  the  products  of  the  distillation 
of  wood. 

CE'LAPRAXITE'LLIS.  A  modern 
southern  constellation,  consisting  of  six- 
teen stars. 

CE'LESTINE  (caelum,  the  sky).  Sul- 
phate of  strontian,  so  named  from  its 
frequently  presenting  a  blue  colour. 

CELLARIAD^.  The  second  family 
of  the  Polypiaria  membranacea  of  Blain- 
ville,  named  from  the  genus  cellaria,  and 
consisting  of  hydriform  animals,  distinct 
from  one  another,  contained  in  mem- 
branous cellules  with  a  bilateral  opening, 
and  comprising  the  flustra,  lunulites,  &c. 

CE'LLULAR  TISSUE  (cellula,  a  little 
cell).  The  elastic  connecting  tissue  of 
the  various  parts  of  animal  and  vegetable 
bodies,  consisting  of  cellules  or  vesicles 
of  various  figures,  adhering  together  in 
masses. 

CELLULARES  {cellula,  a  little  cell). 
Cellular  plants ;  those  which  consist,  in 
many  cases,  entirely  of  cells,  and  have 
no  flowers  or  spiral  vessels.  They  are 
also  called  cryptogamous  and  acotyledo- 
nous  plants.     See  Vasculares. 

CEMENT.  A  preparation  made  of 
various  materials,  which  is  applied  in  a 
soft  state,  and  afterwards  hardens  and 
unites  the  surfaces  to  which  it  is  applied. 

Roman  Cement.  A  mortar  made  of 
lime,  and  puzzolano  ground  to  fine 
powder.  The  latter  substance  consists 
principally  of  pumice,  found  near  Poz- 
zuoli. 

CEMENTATION.  A  process  by  which 
the  properties  of  a  body  are  changed,  on 
being   surrounded  with  the  powder    of 
72 


other  bodies,  and  exposed  to  a  high 
temperature,  as  the  conversion  of  iron 
into  steel,  by  cementation  with  charcoal. 
The  substance  so  employed  is  called 
cement  powder. 

CENTAURUS.  The  Centaur ;  a  south- 
ern constellation,  consisting  of  thirty-five 
stars. 

CENTRAL  ECLIPSES.  A  term  ap- 
plied to  annular  eclipses,  because  the 
centres  of  the  sun  and  of  the  moon  ap- 
pear to  coincide. 

CENTRAL  FORCES.  The  forces 
which  cause  a  moving  body  to  tend 
towards,  or  recede  irom,  the  centre  of 
motion. 

CENTRAL  MOTION.  A  curvilinear 
motion  round  that  point  of  a  body  which 
is  called  the  centre  of  gravity,  resulting 
from  the  balance  of  the  centripetal  and 
the  centrifugal  or  tangential  forces. 

CENTRI'FUGAL  FORCE  {centrum, 
a  centre,  fugio,  to  avoid).  The  force  by 
which  all  bodies,  when  set  in  motion 
round  a  centre,  tend  to  move  uniformly 
in  a  straight  line,  and  thus  to  fly  from  the 
centre,  in  a  tangent  to  the  circle  in  which 
they  move. 

Centrifugal  Evolution.  Leaving  the 
centre ;  a  term  applied  to  inflorescences, 
in  which  the  central  flowers  open  first. 

CENTRI'PETAL  FORCE  (centrum, 
a  centre,  pelo,  to  seek).  The  force  or 
gravity  by  which  a  body  tends  towards 
some  point  as  a  centre  :  in  obedience  to 
this  law  all  the  planets  are  drawn  to  the 
centre  of  their  respective  orbits,  and  all 
bodies  tend  towards  the  centre  of  the 
earth. 

Centripetal  Evolution.  Approaching 
the  centre ;  a  term  applied  to  inflores- 
cences, in  which  the  marginal  flowers 
open  first. 

CEPHALA'NTHIUM  (ne<pa\n,  the 
head,  avOo?,  a  flower).  A  head  of  flowers  ; 
a  designation  of  the  inflorescence  of 
Compositae,  more  commonly  called  a 
capitulum  or  anthodium. 

CE'PHALOTHO'RAX  (Ke</.aA^,  the 
head,  Owpat-,  the  thorax).  The  anterior 
division  of  the  body  in  spiders,  scorpions, 
&c,  which  consists  of  the  head  and  chest 
blended  together,  answering  to  the  first 
two  segments  of  insects  in  a  confluent 
state. 

CEPHALO'PODA  (/ce^aX^,  the  head, 
7roi»9,  7to56p,  a  foot).  A  group  of  mollus- 
cous invertebrate  animals,  in  which  the 
head  is  situated  between  the  trunk  and 
the  feet,  or  principal  organs  of  locomo- 
tion, as  in  the  cuttle-fish. 


CER 


CET 


CE'PHEUS.  A  northern  constellation, 
consisting  of  thirty-five  stars,  the  prin- 
cipal of  which  is  Alderamin. 

CERAMBY'ClDiE.  A  family  of  Co- 
leopterous insects,  of  the  section  Longi- 
cornis  of  Latreille,  named  from  the  genus 
cerambyx,  and  chiefly  characterized  by 
the  great  length  of  the  antennae. 

CE'RASIN  (cerasus,  the  cherry).  A 
gummy  substance,  procured  from  the 
cherry  and  the  plum-tree,  which  swells 
in  cold  water,  but  does  not  readily  dis- 
solve in  it. 

CERA'TIUM  (/cepftTtoi/,  a  little  horn). 
A  compound  fruit,  which  is  one-celled, 
many-seeded,  superior,  linear,  dehiscent 
by  two  valves  separating  from  the  re- 
plum,  and  differing  from  the  siliqua  in 
the  lobes  of  the  stigma  being  alternate 
with  the  placenta,  instead  of  opposite. 
It  has  been  termed  capsula  siliquiformis. 
It  occurs  in  glaucium,  the  horned  pop- 
py, &c. 

CE'RCjE  («ep«op,  a  tail).  The  feelers 
which  project  from  the  hind  part  of  the 
body  in  some  insects. 

CERCA'RLE  (Kepxo?,  a  tail).  A  de- 
signation of  those  animalcules  whose 
body  is  terminated  by  a  tail-like  ap- 
pendage. 

CERCO'PIDjE.  A  family  of  the  tri- 
merous  Homoptera,  remarkable  for  their 
grotesque  forms,  and  represented  in  this 
country  by  the  cuckoo-spits  and  the  frog- 
hoppers,  so  named  from  the  frothy  secre- 
tion which  covers  them  in  their  larva 
and  pupa  states. 

CE'REBRIC  ACID  (cerebrum,  the 
brain).  A  peculiar  acid  found  in  the  sub- 
stance of  the  brain,  containing  phos- 
phorus. 

CERES.  A  telescopic  planet,  situated 
in  the  solar  system,  between  Mars  and 
Jupiter.  It  revolves  round  the  sun  in 
about  4J  years,  and  is  about  264,000,000 
of  miles  distant  from  it.  It  was  dis- 
covered on  Jan.  1st,  1801,  by  M.  Piazzi, 
whose  name  it  sometimes  bears. 

CE'RIC  ACID  (cera,  wax).  An  acid 
produced  by  the  action  of  the  fixed  al- 
kalies on  wax. 

CE'RIN  {cera,  wax).  1.  That  consti- 
tuent of  common  wax  which  dissolves  in 
alcohol.  2.  A  peculiar  substance  pro- 
cured by  the  action  of  alcohol  on  grated 
cork.    3.  A  variety  of  allanite. 

CE'RITE.  A  rare  mineral,  consisting 
of  the  siliciferous  oxide  of  cerium. 

CERPTHIN.E.      The   Club-shells;    a 
sub-family  of  the  Strombidce,  or  Wing- 
shells,  named  from   the    typical   genus 
73 


Cerithium,  and  characterized  by  their 
clavate  form  ;  the  spire  is  very  long ;  the 
outer  lip  considerably  dilated  ;  the  base 
either  truncate,  or  forming  a  short  re- 
curved channel. 

CE'RIUM.  A  white  metal  found  in 
two  Swedish  minerals  called  cerite  and. 
cerine,  and  more  recently  in  allanite,  at 
Alluk,  in  East  Greenland. 

CE'RNUOUS  (cernuus,  hanging  down 
the  head).  Drooping;  inclining  from  the 
perpendicular  towards  the  horizon;  a 
term  applied  to  flowers. 

CERTHI'ADiE  {certhia,  the  tree- 
creeper).  A  family  of  the  Insessores,  or 
Perching  birds,  consisting  of  the  Tree- 
creepers,  Nuthatches,  &c,  which  re- 
semble the  Melliphagidae,  or  Honey- 
suckers,  in  general  structure.  See 
Tenuirostres.  According  to  Macgillivray 
these  birds  constitute  a  family  of  the 
Reptatrices,  or  Creepers,  characterized, 
by  having  the  three  fore  toes  more  or 
less  united  at  the  base  and  spreading 
little. 

CE'RULIN  (cceruleus,  blue).  The 
name  given  to  indigo  in  the  modified, 
state  which  it  acquires  during  solution. 

CE'RUSE.  Carbonate  of  lead,  occur- 
ring naturally  in  the  form  of  carbonate 
of  barytes.  Under  the  name  of  white 
lead,  it  is  employed  by  painters  to  give 
body  to  their  colours. 

CERVI'COBRANCHIA'TA  (cervix, 
the  neck,  fipafxta,  gills).  The  name  of 
an  order  of  Gasteropods,  comprising,  ac- 
cording to  Blainville's  arrangement,  the 
patellae  or  limpets,  and  three  other 
genera.  The  order  is  subdivided  into 
the  retifera  and  the  branchifera ;  the 
former  are  the  patellae,  which  he  sup- 
poses to  respire  by  means  of  a  net-work 
belonging  to  the  cavity  which  is  above 
their  head. 

CE'RVID^E  (cervus,  a  stag).  The 
Stag  tribe  ;  a  family  of  the  Ruminantia, 
in  which  the  antlers  are  periodically  cast 
off. 

CESTOI'DEA  (kco-to?,  a  girdle,  ei<5or, 
form).  Tape-worms ;  an  order  of  the 
Enfozoa,  which  have  a  long,  depressed, 
flat,  tape-like,  articulated  form,  each  seg- 
ment having  distinct  nutritive  and  gene- 
rative organs. 

CETA'CEA  (cete,  a  whale).  An  order 
of  vertebrated  mammiferous  animals 
inhabiting  the  ocean,  as  the  whale,  the 
dolphin,  &c.  These  animals  resemble 
fishes  in  shape,  but  they  breathe  air,  have 
warm  blood,  and  a  double  circulation, 
like  other  mammalia  j  the  tail-fin  is  also 
E 


CH  A 


CH  A 


horizontal,  and  not  vertical,  as  in  true 
fishes. 

CETIC  ACID  {cete,  a  whale).  An  acid 
procured  from  spermaceti,  consisting  of 
margarine  and  fatty  matter.  Cetine  is  a 
white  laminated  substance,  constituting 
pure  spermaceti. 

CETONIA'D,E.  A  family  of  Coleo- 
pterous insects,  of  the  section  Melitophili 
of  Latreille,  named  from  the  genus  ceto- 
nia,  of  which  the  common  rose  beetle 
affords  a  good  example,  and  presenting 
one  of  the  most  extensive  as  well  as  the 
most  brilliant  of  the  beetle  tribes. 

CETUS.  The  Whale  ;  a  southern  con- 
stellation, containing  ninety-seven  stars, 
the  principal  of  which  is  Menkar. 

CETYL.  The  supposed  radical  of  a 
series  of  compounds  derived  from  sperma- 
ceti. 

CEVA'DIC  ACID.  Sabadillic  acid. 
A  crystalline  fatty  acid,  obtained  by 
saponification  of  the  oil  of  cebadilla,  or 
the  seeds  of  the  Asagrcea  officinalis. 

CEY'LANITE.  A  mineral  found  in 
Ceylon,  termed  by  Haiiy,  pleonaste. 

CHA'BASITE.  A  mineral  found  in 
the  fissures  of  some  trap  rocks,  and  in 
the  hollows  of  certain  geodes  disseminated 
in  the  same  rocks. 

CHAFF  OF  RECEPTACLE.  A  term 
popularly  applied  to  the  paleae,  or  the 
membranous,  colourless  bracts,  placed 
between  the  florets  upon  the  receptacle 
of  Composite. 

CHALA'ZA  (xaXa^a,  a  small  swelling). 
A  small  brown  spot  observed  at  the  apex 
of  some  seeds,  as  of  the  Orange,  formed 
by  the  union  of  certain  vessels  proceeding 
from  the  hilum. 

CHALCE'DONY.  A  silicious  simple 
mineral,  uncrystallized,  entering  into  the 
composition  of  agates,  and  found  at  Chal- 
cedon  in  Bithynia.  It  is  of  a  uniform 
milky  white  or  pale  yellow  colour,  often 
with  a  wavy  internal  structure,  and  a 
peculiar  mammillary  surface. 

CHALCFDID.E.  A  family  of  Hymeno- 
pterous  insects,  of  the  section  Pupivora 
of  Latreille,  named  from  the  genus  chal- 
ets, and  characterized  by  minuteness  of 
size,  brilliancy  of  colours,  and  the  general 
absence  of  nervures  from  the  wings. 

CHALK.  Carbonate  of  lime.  In  Geo- 
logy, a  rock  which  forms  the  higher 
part  of  the  cretaceous  group. 

CHALYBEATE  WATERS.  Ferru- 
ginous waters.  Mineral  waters,  whose 
predominating  or  active  principle  is  iron. 
There  are  two  kinds:  the  carbonated, 
containing  carbonate  of  the  protoxide  of 
74 


iron  ;  and  the  sulphated,  containing  sul- 
phate of  iron.  Some  of  the  latter  con- 
tain sulphate  of  alumina,  and  are  called 
aluminous  sulphated  chalybeate*.  » 

CHAMA'CEiE.  Clamp-shells  ;  an  or- 
der of  the  conchiferous  Mollusca,  named 
from  the  chama ;  in  these,  the  mantle  is 
closed,  with  the  exception  of  three  aper- 
tures, two  of  which  are  for  the  ingress 
and  egress  of  water,  and  the  third  for  the 
passage  of  the  foot,  which  is  here  usually 
more  powerful. 

CHAMjE'LEON.  A  modern  southern 
constellation,  consisting  of  ten  stars. 

CHAM^E'LEO'NIDJE.  The  Chame- 
leon tribe ;  a  family  of  Saurian  reptiles, 
characterized  by  their  extraordinary 
length  of  tongue,  and  by  the  adaptation 
of  their  feet  and  tail  for  climbing. 

CHAMBERED.  Divided  internally 
into  chambers  or  compartments,  as  the 
testaceous  cephalopods,  or  the  nautilus. 

CHAMELEON  MINERAL.  A  com- 
bination of  black  oxide  of  manganese 
and  potash,  which  gives  a  green  colour 
to  water,  passes  gradually  through  all  the 
shades  of  the  prism,  and  at  last  becomes 
colourless. 

CHA'MID^E.  A  family  of  macrotra- 
chian  Bivalves,  named  from  the  typical 
genus  chama;  in  these  animals  the 
length  of  the  siphons,  which  charac- 
terizes the  tribe,  is  much  reduced. 

CHARA'CE^E.  A  small  family  of 
cryptogamous  plants,  consisting  of  the 
two  genera  chara  and  nitella.  These  are 
submerged  aquatic  plants,  interesting  to 
the  physiologist,  as  displaying  the  special 
circulation,  or  cyclosis,  in  vegetables. 

CHARADRI'ADjE  (charadrius,  the 
plover).  The  Plover  tribe ;  a  family  of 
the  Grallatores,  or  Wading  birds,  in 
which  the  bill  is  of  moderate  size,  and 
the  hinder  toe  either  entirely  deficient, 
or  not  long  enough  to  reach  the  ground. 

CHARCOAL*.  The  residue  of  animal, 
vegetable,  and  many  mineral  substances, 
when  heated  to  redness  in  close  vessels. 

CHARLES'S  WAIN.  Seven  con- 
spicuous stars  in  Ursa  Major  or  the 
Great  Bear. 

CHART  {charta,  paper).  A  geographi- 
cal or  nautical  representation  of  a  portion 
of  the  earth's  surface  on  paper,  according 
to  a  scale  which  regulates  the  relative 
proportion  of  the  parts.  Geographical 
charts,  being  of  a  general  character,  are 
commonly  called  maps;  but  nautical  or 
marine  charts  are  particularly  devoted  to 
delineations  of  a  coast  and  part  of  the 
adjacent  sea. 


CHE 


CHL 


Marine  charts  are  constructed  in  two 
ways.  1.  A  plane  chart  represents  the 
meridians,  as  well  as  the  latitudes,  by 
equidistant  and  parallel  straight  lines ; 
and,  consequently,  the  longitudes  and 
latitudes  appear  equal,  differing  from  the 
fact.  2.  A  Mercator's  chart  represents 
the  meridians  as  well  as  the  circles  of 
latitude  by  parallel  straight  lines;  but 
the  distances  of  the  latter  increase  in  a 
determinate  ratio  from  the  equator  to  the 
poles. 

CHEILO'GNATHA  (xelAor,  a  lip, 
fvdOos,  a  jaw).  An  order  of  Myriapods 
or  Centipedes,  in  which  the  two  man- 
dibles and  the  tongue  are  united  to  form 
a  large  lower  lip. 

CHEILO'PODA  (xeTXop,  a  lip,  now, 
tto56?,  a  foot).  A  family  of  insects,  of 
the  class  Myriapoda,  or  Centipedes,  in 
which  the  lower  lip  is  formed  by  a  pair 
of  feet. 

CHEIRO'PTER  A  (Xelp,  a  hand,  nrepbv, 
a  wing).  An  order  of  mammiferous 
quadrupeds,  which  have  their  extremities 
connected  together  by  a  wing-like  expan- 
sion of  the  integuments,  for  the  purpose 
of  flight,  as  in  the  bat. 

CHELE'  {xh^)-  A  claw;  particularly 
applied  to  the  bifid  claw  of  the  Crustacea, 
the  scorpion,  &c. 

CHELI'CERA  (x^/Xn,  a  claw,  nepa?,  a 
horn).  The  prehensile  claws  of  the 
scorpion,  which  are  the  homologues  of 
antennae. 

CHELIOSO'MID,E.  A  tribe  of  bi- 
valved  mollusca,  which  have  a  cartila- 
ginous covering,  analogous  to  that  of  the 
chitons  and  the  tortoises. 

CHELO'NIA  (xeXwi/»i,  a  turtle).  An 
order  of  Reptiles,  which  have  their  ribs 
immoveable,  comprising  the  tortoises, 
the  turtles,  &c.  The  body  of  these  ani- 
mals is  enclosed  in  a  shell,  the  upper  and 
arched  portion  of  which  is  termed  the 
carapace;  the  lower  plate  is  called  the 
plastron. 

CHELO'NIDjE  (xeXtovn,  a  turtle).  The 
Turtles ;  a  family  of  Chelonian  reptiles, 
distinguished  by  the  incompleteness  of 
their  shelly  covering,  and  by  the  pecu- 
liar modification  of  the  feet  for  swim- 
ming. 

CHEMICAL  ATTRACTION.  Elec- 
tive attraction  or  affinity.  These  terms 
denote  the  action  by  which  the  particles 
of  one  class  of  bodies,  when  presented  to 
those  of  certain  other  classes,  unite  to 
form  new  compounds,  making  a  choice, 
or  election,  of  those  with  which  they 
unite. 
75 


CHEMICAL  COMBINATION.  An 
intimate  union  of  two  or  more  substances, 
which  forms  a  compound  differing  in 
one  or  more  of  its  essential  qualities 
from  those  of  its  constituent  bodies. 

CHEMISTRY.  A  term,  of  Arabic 
origin,  signifying  the  knowledge  of  the 
composition  of  bodies,  and  of  the  changes 
of  constitution  produced  by  their  mutual 
action  on  each  other. 

CHENOPODIA'CE^E.  The  Goosefoot 
tribe  of  Dicotyledonous  plants,  comprising 
beet,  mangel  wurzel,  spinach,  &c.  Her- 
baceous plants  or  undershrubs,  with 
leaves  alternate ;  flowers  small ;  stamens 
inserted  into  the  base  of  the  calyx ;  ovary 
superior ;  fruit  membranous. 

CHERT.  A  silicious  mineral,  nearly 
allied  to  chalcedony  and  flint,  but  less 
homogeneous  and  simple  in  texture.  A 
gradual  transition  from  chert  to  lime- 
stone is  not  uncommon. 

CHIAROSCU'RO  (chiaro,  light,  os- 
euro,  dark).  In  painting,  the  judicious 
arrangement  and  combination  of  light 
and  shade,  and  of  bright  and  dark 
colours. 

CHIA'STOLITE.  A  mineral  found 
imbedded  in  clay-slate,  resembling  stea- 
tite. Chiastolite- state,  or  rather  clay- 
slate,  is  a  division  of  the  Cumbrian  group 
of  rocks;  it  is  dark-coloured,  and  gene- 
rally soft,  containing  crystals  of  the  mine- 
ral chiastolite. 

CHI'LDRENITE.  A  mineral  found 
in  Devonshire,  consisting  of  a  phosphate 
of  alumina  and  iron. 

CHINA-CLAY.  Kaolin.  A  variety 
of  clay  prepared  from  decaying  granite. 

CHINA  GLAZE.  A  preparation  for 
printing  blue  frit,  made  from  ten  parts 
of  glass,  two  parts  of  lead,  and  three  or 
more  of  blue  calx. 

CHINCHI'LLID,E.  The  chinchilla 
tribe ;  a  small  family  of  the  Rodentia,  in- 
digenous in  South  America,  and  valuable 
in  commerce  for  their  furry  skins. 

CHI/TINE  (x<twv,  a  tunic).  A  prin- 
ciple discovered  in  beetles  and  other  in- 
sects, also  called  entomoline,  and  consist- 
ing of  the  base  of  their  external  skeleton. 

CHITO'NID^E.  A  family  of  Gastero- 
pods,  named  from  the  genus  Chiton,  and 
characterized  by  the  presence  of  a  pro- 
tecting tunic-like  shell,  formed  of  many 
portions,  which  are  often  in  contact  and 
overlap  one  another. 

CHLORATES.  The  salts  of  chloric 
acid,  formerly  called  hyper-oxy muriates. 
The  principal  are  those  of  potash  and 
baryta. 

E2 


CHO 


CHR 


CHLORIMETRY.  The  process  of  esti- 
mating the  bleaching  power  of  chloride 
of  lime,  by  the  quantity  of  a  solution 
of  sulphate  of  indigo  which  a  known 
weight  of  chloride  can  discolour  or  render 
yellow. 

CHLORINE  (xXcapof,  green).  A  green- 
ish gas,  obtained  by  the  action  of  mu- 
riatic acid  on  peroxide  of  manganese.  It 
was  first  described  under  the  name  of 
dephlogisticated  marine  acid,  and  was 
afterwards  called  oxy-muriatic  acid.  Its 
compounds,  which  are  not  acid,  are  called 
chlorides  (or  chlorurets),  and  are  charac- 
terized by  the  same  prefixes  as  the  oxides. 
CHLORITE  (xXwpor,  green).  A  fri- 
able mineral,  of  a  green  colour,  allied  in 
characters  to  talc  and  mica.  It  occurs  dis- 
persed in  rocks,  or  forms  beds  of  itself. 
The  species  are  chlorite  earth,  common 
chlorite,  chlorite  slate,  and  foliated  chlo- 
rite. 

CHLORFTIC  SAND  (xXwpof,  green). 
Sand  coloured  green  by  an  admixture  of 
the  simple  mineral  chlorite. 

CHLOROCARBONIC  ACID  GAS.  An 
acid  termed  by  Davy  phosgene  gas,  con- 
sisting of  chlorine  and  carbonic  acid. 

CHLO'ROPAL.  A  silicate  of  iron,  a 
mineral  found  associated  with  copal ;  its 
varieties  are  the  conchoidal  and  the 
earthy. 

CHLO'ROPHANE  (x^copof,  green, 
<paivu>,  to  shine).  A  variety  of  fluor  spar, 
which  gives  out  an  emerald  green  light 
by  the  mere  heat  of  the  hand. 

CHLOROPHCE'ITE.  A  green  mineral 
found  imbedded  in  basalt  or  in  black  in- 
durated ironstone. 

CHLO'ROPHYLLE  (x^wpor,  green, 
(pvWov,  a  leaf).  The  green  colouring 
matter  of  leaves.    See  Chromule. 

CHLOROUS  POLE.  A  term  founded 
on  the  theory  that  the  particles  of  matter 
are  susceptible  of  polarity.  Hence  that 
pole  of  a  particle  of  zinc  or  of  hydro- 
chloric acid,  which  has  the  attraction  or 
affinity  which  is  characteristic  of  chlo- 
rine, or  chlorous  attraction,  is  called  the 
chlorous  pole.     See  Zincous  pole. 

CHOKE  DAMP.  The  name  given  by 
miners  to  carbonic  acid  gas,  which  is  apt 
to  be  formed  and  to  accumulate  in  coal- 
mines. 

CHO'NDROPTERY'GII  (x6v3pof,  car- 
tilage, Tr-repuf,  a  fin).  Cartilaginous  fishes ; 
one  of  the  primary  divisions  of  the  class 
Pisces,  so  named  from  their  skeleton  con- 
taining little  calcareous  matter,  and  this 
disposed,  not  in  fibres  or  plates,  as  in  Osse- 
ous fishes,  but  in  small  granules.  There 
76 


are  two  orders  of  these  fishes,  viz.  those 
with  free  gills,  as  the  sturgeons,  and  those 
with  fixed  gills,  in  which  the  external 
edge  of  the  gills  is  attached  to  the  skin, 
as  the  sharks,  rays,  and  lampreys. 

CHORD  OF  AN  ARC  (chorda  arc&s, 
the  string  of  a  bow).  The  straight  line 
which  joins  the  two  extremities  of  a  curve 
or  arc.  To  find  the  chord  of  a  given  arc, 
find  the  angle  subtending  the  arc ;  then,  to 
find  the  chord  of  the  angle,  multiply  the 
diameter  by  the  sine  of  half  the  angle. 

CHORD  IN  MUSIC.  A  combination 
of  three  or  more  harmonious  sounds. 
1.  The  perfect  chord  consists  of  any  given 
note  combined  with  a  major  3rd  and  a 
perfect  5th;  this  and  its  inversions  are 
called  consonant  chords.  2.  The  chord  of 
the  seventh,  or  dominant  seventh,  con- 
sists of  any  given  note,  combined  with  a 
major  3rd,  a  perfect  5th,  and  a  minor  7th ; 
this  and  its  inversions  are  called  dis- 
sonant chords. 

CHOROGRAPHY  (%<apa,  a  country, 
7pa0a>,  to  describe).  The  description  of 
countries ;  a  term  differing  from  geo- 
graphy, as  a  part  differs  from  the  whole. 
CHREMATFSTICS  {XPW*Ta,  wealth). 
The  name  given  by  continental  writers  to 
that  branch  of  political  economy  which 
relates  to  the  wealth  of  nations. 

CHROMA'TIC  SCALE  {xp&H^  co- 
lour). The  scale  of  semitones  employed 
in  music.  The  term  chromatic  either 
denotes  that  the  musical  characters  were 
written  in  colours,  or  suggests  the  variety 
of  shades  which,  figuratively,  charac- 
terize this  scale.  By  chromatic  music  is 
usually  meant  that  in  which  extreme 
intervals  are  used. 

CHROMATICS  (xp^/ua,  colour).  That 
branch  of  optics  which  treats  of  the 
colours  of  light,  their  several  properties, 
and  the  laws  by  which  they  are  sepa- 
rated. 

CHROME  ALUM.  A  term  applied 
to  a  crystallizable  double  salt,  consisting 
of  sulphate  of  chromium.  This  salt  is 
isomorphous  with  alum,  and  analogous 
to  it  in  constitution,  but  the  alumina  is 
replaced  by  oxide  of  chromium. 

CHROME  IRON.  Chromate  of  iron  ; 
one  of  the  ores  containing  chromium; 
it  occurs  massive  and  crystallized. 

CHROME  YELLOW.  A  well-known 
pigment,  consisting  of  chromate  of  lead. 

CHRO'MIUM  (xpwMa,  colour).  A 
metal  found  in  a  Siberian  mineral,  called 
chromate  of  lead,  or  red  lead,  and  named 
from  its  remarkable  tendency  to  form 
coloured  compounds.    It  combines  with 


CHR 


CIN 


oxygen  and  forms  chromic  acid,  the  sa- 
line compounds  of  which  are  called  chro- 


CHRO'MULE  {xpuna,  colour).  The 
name  of  the  colouring  matter  of  plants. 
It  has  been  also  termed  chlorophylle ;  but 
as  the  latter  term  merely  expresses  the 
greenness  of  leaves,  it  is  inapplicable  to 
the  variously  coloured  granules  found  in 
vegetable  tissue. 

CHRONO'LOGY  {xpovot,  time,  X6- 
709,  description).  The  arrangement  of 
historical  events  according  to  the  order 
of  time.  Dates  are  to  History,  what 
the  latitude  and  longitude  are  to  Naviga- 
tion, fixing  the  exact  position  of  the 
object  to  which  they  are  applied. 

CHRONO'METER  (xpovor,  time,  fxe- 
rpov,  measure).  A  time-keeper ;  an  in- 
strument used  for  determining  the  longi- 
tude at  sea,  and  for  the  purpose  of  mea- 
suring accurately  small  periods  of  time. 
It  differs  from  a  common  watch  in  having 
a  detached  escapement,  and  a  compensa- 
tion for  heat  and  cold. 

CHRY'SALIS  (xpixtop,  gold).  A  fan- 
ciful name  for  the  nymph  or  pupa  state 
of  insect  life,  from  the  glittering  spots  of 
golden  hue  with  which  the  animal  is 
sometimes  speckled. 

CHRY'SENE.  A  substance  found 
among  the  products  of  the  distillation  of 
wood. 

CHRYSI'DIDjE.  A  family  of  Hyme- 
nopterous  insects,  of  the  section  Pupi- 
vora,  named  from  the  genus  chrysis,  and 
remarkable  for  their  brilliant  colours. 
Some  of  them  are  termed  ruby-tail  flies. 

CHRYSOBA'LANACEjE.  The  Cocoa- 
plum  tribe  of  Dicotyledonous  plants, 
nearly  allied  to  Rosaceae,  from  which 
they  differ  in  having  a  style  proceeding 
from  the  very  base  of  the  ovary,  and 
irregular  stamens  and  petals.  The  fruit 
of  Chrysobalanus  Icaco  is  eaten,  in  the 
West  Indies,  under  the  name  of  cocoa- 
plum. 

CHRY'SOBERYL.  A  green  gem,  con- 
sisting of  glucina  and  alumina,  occurring, 
massive  and  crystallized,  in  North  Ame- 
rica and  Brazil.  It  is  the  cymophane  of 
Haiiy. 

CHRY'SOLITE.  A  precious  stone 
brought  from  the  Levant,  termed  peridot 
by  Haiiy.  Ure  says  that  chrysolite  is  the 
topaz  of  the  ancients,  while  our  topaz  is 
their  chrysolite.  A  variety  called,  from 
its  colour  olivine,  occurs  in  basalt  in 
Germany.  Chusite  is  said  to  be  another 
variety  of  this  gem. 

CHRY'SOPRASE.   A  rare  apple-green 
77 


chalcedony,  found  in  Silesia,  which  owes 
its  colour  to  the  presence  of  nickel. 

CICA'DIDiE  {cicada,  a  cricket).  The 
Cricket  tribe;  a  family  of  the  trimerous 
Homoptera,  characterized  by  their  power 
of  producing  a  shrill,  continuous  sound, 
by  means  of  a  peculiar  apparatus  situated 
beneath  the  abdomen. 

CICA'TRICULE  {cicatrix,  a  scar). 
A  little  scar ;  the  scar  formed  by  the 
separation  of  a  leaf  from  its  stem.  A 
stem  so  marked,  is  said  to  be  scarred  or 
cicatrized. 

CICHORACEiE.  A  division  of  the 
Compositae,  in  which  the  florets  are  all 
ligulate,  the  juice  usually  milky,  bitter, 
astringent,  and  narcotic,  as  in  cichorium 
or  succory,  endive,  and  some  species  of 
lettuce. 

CICINDE'LID^.  A  family  of  Coleo- 
pterous insects,  named  from  the  typical 
genus  cicindela,  and  distinguished  by  the 
presence  of  six  palpi,  and  by  their  de- 
riving their  subsistence  on  the  land. 

CI'LIA  {cilium,  an  eye-lash).  A  term 
used  to  designate  a  peculiar  sort  of  mov- 
ing organs,  resembling  microscopic  hairs. 
The  terms  ciliary  motion  and  vibratile 
motion  have  been  employed  to  express 
the  appearance  produced  by  the  moving 
cilia.  Any  part  is  said  to  be  ciliated 
which  is  fringed  Kith  hairs,  as  the  margin 
of  some  leaves. 

CILIOBRA'CHIATE  {cilia,  vibratile 
hairs,  brachium,  the  arm).  A  term  ap- 
plied by  Dr.  Arthur  Farre  to  those  polyps, 
whose  arms  are  covered  with  cilia,  form- 
ing important  agents  in  securing  prey. 
These  are  the  bryozoa  of  Ehrenberg,  and 
are  ranged  among  the  tubular  polyps  of 
Cuvier. 

CILIO'GRADA  {cilia,  vibratile  hairs, 
gradior,  to  advance).  A  group  of  the 
Acalephce,  in  which  the  organs  of  motion 
consist  of  vibratile  cilia  disposed  upon 
the  surface  of  the  body,  which  in  their 
motions  and  office  resemble  those  of  the 
polygastric  animalcules. 

CIMI'CID^.  A  family  of  Hemipte- 
rous  insects,  named  from  the  "  familiar 
beast"  cimex.  or  the  bug. 

CI'MOLITE.  Cimolian  earth.  A  hy- 
drous silicate  of  alumina,  found  in  the 
island  of  Cimola,  used  for  the  same  pur- 
poses as  fuller's  earth. 

CINCHONA'CEjE.  The  Cinchona 
tribe  of  dicotyledonous  plants.  Trees  or 
shrubs  with  leaves  opposite ;  flowers  in 
panicles;  stamens  arising  from  the  co- 
rolla ;  fruit  inferior,  either  splitting  into 
two  cocci  or  indehiscent. 

£3 


cm 


cm 


CINE'NCHYMA  (4*fc*  to  move, 
67xuM«>  infusion).  A  botanical  terra  ap- 
plied to  the  laticiferous  tissue  in  plants, 
distinguished  by  its  irregular  branching 
and  anastomozing  character. 

CI'NGULUM.  Literally,  a  girdle.  In 
Zoology,  the  neck  of  a  tooth.  The  term 
cingula  denotes  the  transverse  series  of 
bony  pieces  connected  by  flexible  joints, 
as  in  the  armour  of  the  armadillo. 

CI'NNABAR.  Sulphuret  of  mercury ; 
the  common  ore  of  mercury,  sometimes 
occurring  crystallized  as  a  beautiful  ver- 
milion. 

CINNAMON  STONE.  A  silicate  of 
lime,  alumina,  and  oxide  of  iron,  brought 
from  Ceylon,  and  named  from  its  colour. 

CI'NNAMYL.  The  hypothetical  radi- 
cal of  the  essence  of  cinnamon  and  of 
cinnamic  acid — an  acid  formed  by  the 
oxidation  of  the  essence  of  cinnamon  in 
air. 

CINNY'RID^.  The  Sun-birds;  a 
family  of  the  Insessores,  or  Perchers, 
named  from  the  genus  cinnyris,  closely 
allied  to  the  Trochilidae,  or  Humming- 
birds, which  they  represent  in  the  Eastern 
Continent.    See  Tenuirostres. 

CITHER  (sifr,  Arabic).  A  term  sig- 
nifying empty,  and  used  as  a  substantive 
to  denote  the  figure  0. 

CI'POLIN.  A  green  marble  with  white 
zones,  brought  from  Rome. 

CI'RCINATE  (circino,  to  make  a 
circle).  Rolled  inwards,  or  spirally  down- 
wards, from  the  point  to  the  base,  as  the 
aestivation  of  certain  plants,  the  deve- 
lopment of  the  young  fronds  of  ferns,  the 
inflorescence  of  Boraginaceous  plants, 
fee. 

CI'RCINUS.  The  Compasses;  a  mo- 
dern constellation,  consisting  of  four 
stars,  not  very  far  from  the  South  Pole. 

CIRCLE  (circulus,  dim.  of  circus,  a 
ring).  A  plane  figure  contained  by  one 
line,  which  is  called  the  circumference, 
and  such  that  all  straight  lines  drawn 
from  a  certain  point  within  the  figure  to 
the  circumference  are  equal  to  one  an- 
other; this  point  is  called  the  centre  of 
the  circle,  and  the  straight  lines,  radii, 
or  rays. 

1.  Circles,  Arctic  and  Antarctic.  Circles 
supposed  to  be  drawn  round  the  Arctic 
and  the  Antarctic  pole,  at  the  distance  of 
about  23^  degrees.  On  the  terrestrial 
globe  these  circles  surround  what  are 
called  the  two  frozen  zones,  or  girdles  of 
the  earth. 

2.  Circle,  Astronomical.  A  term  usually 
applied  to  an  astronomical  instrument,  of 

78 


which  the  sole  or  principal  use  is  the 
measurement  of  angles  of  altitude,  or 
zenith  distance. 

3.  Circles,  Co-ordinate.  Two  circles  at 
right  angles  to  each  other ;  or  two  circles, 
one  of  which  passes  through  the  pole  of 
the  other.  By  reference  to  two  such 
circles  a  point  in  the  sphere  is  deter- 
mined: e.g.,  on  the  earth,  by  determin- 
ing the  longitude  and  latitude;  in  the 
starry  heavens,  by  the  right  ascension 
and  declination;  in  the  visible  hemi- 
sphere, by  the  azimuth  and  altitude. 

4.  Circles,  Concentric.  Circles  which 
have  the  same  centre,  the  one  surround- 
ing the  other,  as  with  a  ring.  Circles 
which  are  wholly  or  partially  surrounded 
by  another,  but  have  different  centres, 
are  termed  eccentric. 

5.  Circle  of  Declination.  A  circle  on 
which  declination  is  measured,  i.  e.  a 
horary  circle  passing  through  the  poles. 
According  to  some  writers  on  Astronomy, 
the  term  denotes  a  parallel  of  any  declina- 
tion, or  the  small  circle,  all  of  whose 
points  have  the  same  declination;  that 
is,  a  parallel  to  the  equator. 

6.  Circles,  Tropical.  Circles  drawn 
parallel  to  the  equator  through  the  sol- 
stices. 

7.  Circle  of  Illumination.  That  imagi- 
nary circle  which  divides  the  enlightened 
hemisphere  of  the  earth  from  the  dark- 
ened hemisphere. 

8.  Circles  of  the  Sphere.  Circles  whose 
planes  pass  through  the  sphere,  and  have 
their  circumference  upon  its  surface.  If 
the  plane  pass  through  the  centre  of  the 
sphere,  it  is  called  a  great  circle ;  if  not, 
it  is  called  a  less  circle.  The  equator  and 
ecliptic  are  great  circles ;  the  polar  circles 
and  the  parallels  of  latitude  or  declina- 
tion, are  small  circles. 

9.  Circles  of  Perpetual  Apparition. 
Small  circles  parallel  to  the  equator,  and 
touching  the  horizon  of  any  given  place. 

10.  Circles  of  Perpetual  Occultation. 
Small  circles  parallel  to  the  equator,  and 
touching  the  lower  part  of  the  horizon, 
or  never  appearing  above  it. 

11.  Circles  of  Position.  Great  circles 
of  the  sphere,  passing  through  the  com- 
mon intersection  of  the  meridian  and 
horizon,  and  through  any  degree  of  the 
ecliptic,  or  centre  of  a  star  or  planet. 

CFRCULAR  PARTS.  The  name  given 
to  Napier's  proposition  in  Trigonometry, 
which  generalizes  the  relations  between 
the  parts  of  a  spherical  right-angled  tri- 
angle under  two  formulas. 

CIRCULAR  VELOCITY.    The  velo- 


CIR 


CIS 


city  of  a  revolving  body,  measured  by  an 
arc  of  a  circle. 

CIRCU'MFERENCE  (circum  fero,  to 
carry  round).  A  line  which  bounds  a 
figure,  commonly  applied  to  curvilinear 
figures.  The  Greek  synonymous  term 
periphery  is,  however,  applied  to  recti- 
linear figures. 

CIRCU'MFEREN'TOR.  An  instru- 
ment used  by  surveyors  for  taking  angles. 

CI'RCUMFLEX  VERBS.  A  term  ap- 
plied by  Greek  grammarians  to  those 
verbs  which  are  also  called  pure  or  con- 
tracted because,  after  contraction,  the  <o 
receives  a  circumflex,  as  <pi\ew,  <pi\a>. 
See  Accent. 

CIRCUMPO  CAR  STARS.  Stars  which 
revolve  round  the  pole,  without  setting  in 
a  given  latitude.  The  number  of  these 
stars  increases  with  the  latitude  of  the 
place,  or  the  elevation  of  the  pole  above 
the  horizon. 

CIRCUMSCFSSILE  (circum,  around, 
scindo,  to  cut).  Divided  around  by  a 
transverse  separation,  as  applied  to  that 
mode  of  dehiscence  of  fruits  which  oc- 
curs in  hyoscyamus,  in  anagallis,  in 
lecythis,  &c. 

CIRRHO'PODA  (mpp6s,  frizzled  hair, 
TToi/c,  7ro36r,  a  foot).  A  class  of  aquatic 
invertebrate  animals,  with  numerous  la- 
teral articulated  cirrhi,  and  their  body 
fixed  in  a  multivalve  shell.  The  class  is 
composed  chiefly  of  the  barnacles  and 
acorn-shells.  The  following  orders  have 
been  distinguished : — 

1.  Balanida,  or  those  which  are  en- 
closed in  fixed,  sessile,  multivalve,  coni- 
cal shells,  as  the  balanus. 

2.  Anatifida,  or  those  which  have  the 
enveloping  shell  attached  by  means  of  a 
long  fleshy  contractile  tubular  peduncle, 
as  in  the  anatifa. — Grant. 

CFRRHOSE  (Kipp6s,  frizzled  hair). 
Any  thing  which  terminates  in  a  tendril, 
or  filiform  appendage,  as  the  leaf  of  seve- 
ral leguminous  plants. 

CFRRI  (plur.  of  cirrus,  a  curl).  The 
curled  filamentary  appendages  which  re- 
present the  feet  of  the  barnacles. 

CIRRFGRADA  (cirrus,  a  curled  lock 
of  hair,  gradior,  to  advance).  A  group 
of  the  Acalephce,  the  lower  surface  of 
some  of  which  is  furnished  with  nume- 
rous appendages,  called  cirri,  which  are 
organs  of  prehension,  and,  it  is  supposed, 
of  progression. 

CFRRIPEDES  (cirrus,  a  curl,  pedes, 
feet).  A  class  of  articulate  animals, 
having  curled  jointed  feet.  See  Cirrho- 
poda. 

79 


CIRRO-CUMULUS  (cirrus,  a  curled 
lock  of  hair,  cumulus,  a  heap).  The 
sonder-cloud ;  an  intermediate  modifica- 
tion of  clouds  between  the  cirrus  and  the 
cumulus.  It  consists  of  extensive  beds 
of  numerous  small  well-defined  orbicular 
masses  of  cloud,  or  small  cumuli,  in  close 
horizontal  opposition,  but  at  the  same 
time  lying  quite  asunder  or  separate  from 
each  other.  The  prevalence  of  this  cloud, 
in  summer,  forebodes  an  increase  of  tem- 
perature ;  in  winter,  the  breaking  up  of 
a  frost,  and  warm  and  wet  weather. 

CIRRO-STRATUS  (cirrus,  a  curled 
lock  of  hair,  stratus,  a  bed  or  covering). 
The  wane-cloud ;  an  intermediate  modi- 
fication of  clouds  between  the  cirrus  and 
the  stratus,  distinguished  by  its  flatness, 
and  great  horizontal  extension  in  pro- 
portion to  its  perpendicular  height.  From 
its  generally  changing  its  figure,  it  has 
been  called  wane-cloud.  Varieties  of  this 
cloud  occur  in  the  mackerel-back  sky  of 
summer  evenings ;  and  in  the  cymoid 
modification,  which  consists  of  small  rows 
of  little  clouds,  curved  in  a  peculiar  man- 
ner. The  prevalence  of  these  clouds  is  a 
sure  sign  of  rain  or  snow ;  the  cymoid 
variety  always  indicates  stormy  weather. 

CFRRUS  (Lat.,  a  lock  of  hair  curled). 
The  curl-cloud ;  a  primary  form  of  clouds, 
characterized  by  its  curling  and  flexuous 
form,  by  the  lightness  of  its  appearance, 
its  fibrous  texture,  and  the  great  and 
perpetually  changing  variety  of  its  figure. 
It  accompanies  a  variable  state  of  the 
weather,  and  forebodes  wind  and  rain. 
The  comoid  cirrus,  vulgarly  called  mare's 
tail,  is  the  proper  cirrus ;  it  resembles  a 
distended  lock  of  white  hair,  or  a  bunch 
of  wool  drawn  out  into  fine  pointed  ends. 
Modifications  of  this  texture  occur  in  the 
linear  cirrus,  in  which  the  lines  of  cloud 
are  parallel ;  and  in  the  reticular  cirrus, 
in  which  they  cross  each  other  in  various 
directions,  presenting  the  appearance  of 
net- work. 

CFSSOID  (uLaraos,  ivy,  6i<5o?,  likeness). 
Resembling  ivy;  a  fanciful  designation 
of  a  curve  line  of  the  second  order,  em* 
ployed  by  the  Greeks  in  the  celebrated 
problem  of  finding  two  mean  propor- 
tionals between  two  given  straight  lines. 

CISTA'CE^E.  The  Cistus  or  Rock- 
rose  tribe  of  Dicotyledonous  plants  ; 
characterized  by  the  fragrant  resinous 
secretion  of  their  leaves,  the  beauty  of 
their  fugitive  flowers,  and  the  produc- 
tion, from  some  of  their  species,  of  the 
green  labdanum. 

CISTE'LIDES.  A  family  of  Coleopte- 
E4 


CL  A 


CLE 


rous  insects,  of  the  section  Heteromera 
and  subsection  Stenelytra,  named  from 
the  genus  cistela. 

CITRATE.  A  salt  formed  by  the  com- 
bination of  citric  acid  with  a  base. 

CI'TRENE  {citrus,  a  lemon).  A  pe- 
culiar carburetted  hydrogen,  constituting 
the  principal  part  of  the  volatile  oil  of 
lemons. 

CITRIC  ACID  (citrus,  a  lemon).  The 
acid  of  limes,  lemons,  &c.  By  exposure 
to  heat,  it  is  decomposed,  with  the  forma- 
tion of  the  pyro-citric  and  citricic  acids. 

CLADE'NCHYMA  (/c\a5of,  a  branch, 
^yxv/Jia,  infusion).  A  modification  of  the 
parenchyma  of  plants,  characterized  by 
its  branched  form. 

CLADO'CERA.  An  order  of  the  bran- 
chiopodous  Crustacea,  in  which  the  cara- 
pace is  formed  like  a  bivalve  shell,  and 
there  are  five  pairs  of  thoracic  members. 
A  characteristic  example  occurs  in  the 
daphnia  pulex,  or  water-flea. 

CLAIRVO'YANCE.  Clearsightedness; 
a  peculiar  mode  of  sensation,  or  second 
sight,  connected  with  somnambulism,  and 
supposed  to  be  diffused  over  the  whole 
surface  of  the  body,  but  to  be  especially 
seated  in  the  epigastrium  and  fingers' 
ends. 

CLARIFICATION  (clarus,  clear,  fio, 
to  become).  The  process  of  clearing 
liquids,  by  subsidence  of  the  suspended 
particles,  and  decantation  of  the  super- 
natant liquor;  by  filtration  through 
porous  substances ;  or  by  coagulation,  or 
the  admixture  of  albumen,  and  the  sub- 
sequent action  of  caloric,  acids,  &c. 

CLA'VATE  {clavus,  a  club).  Club- 
shaped  ;  a  form  in  which  one  extremity 
is  slender  and  pointed,  while  the  other  is 
thick  and  obtuse,  as  in  many  of  the  zoo- 
phagous  mollusca;  in  filaments,  styles, 
and  the  vittae  of  umbelliferous  plants. 

CLAVICO'RNES  (clavus,  a  club,  cornu, 
a  horn).  A  family  of  the  pentamerous 
Coleoptera,  characterized  by  the  club- 
shaped  form  of  the  extremities  of  the 
antennae,  the  terminal  points  frequently 
forming  a  club. 

CLAW  OF  PETAL.  The  narrow  part 
at  the  base  of  some  petals,  which  is  ana- 
logous to  the  foot-stalk  of  a  leaf,  as  in 
the  pink. 

CLAY.  An  argillaceous  rock,  of  an 
unctuous,  soft,  friable,  and  dense  homo- 
geneous texture,  forming  a  tenacious 
paste  with  water,  and  of  various  colours. 
The  varieties  of  clay  are  essentially  sili- 
cates of  alumina. 

1.  Indurated  Clay  is  a  variety  of  trap 
80 


rocks,  with  a  dull  earthy  fracture,  vary- 
ing in  colour  from  greenish-grey  to  grey- 
ish-white, or  red,  or  brown,  or  even 
black. 

2.  Kimmeridge  Clay  is  a  subdivision  of 
the  Upper  Oolite  Formation,  of  a  blue 
or  yellowish  colour,  more  or  less  slaty  or 
passing  into  slate,  sometimes  so  impreg- 
nated with  bitumen  as  to  be  used  for 
fuel,  and  containing  remains  of  saurian 
reptiles  and  shells. 

3.  Oxford  Clay,  or  Clunch  Clay,  is  also 
a  subdivision  of  the  Middle  Oolite  Forma- 
tion, of  a  dark  blue  colour ;  some  of  the 
beds  are  bituminous,  and  abound  in  sep- 
taria,  or  masses  having  internal  dissepi- 
ments. In  its  lower  part  are  beds  of 
Kelloway  rock,  calcareous  grit  or  sand- 
stone, coral  rag  and  oolite,  and  calcareous 
sandstone. 

4.  Weald  Clay.  The  upper  portion  of 
the  Wealden  Formation,  composed  of 
beds  of  clay  of  a  bluish  or  brownish 
colour,  sandstone,  calcareous  sandstone, 
conglomerate,  limestone,  and  iron-stone. 
The  mass  contains  scales  of  mica,  iron- 
pyrites,  crystals  of  selenite,  and  traces  of 
lignite. 

CLAY  IRON-ORE.  One  of  the  ferri- 
ferous rocks  from  which  iron  is  procured 
in  great  abundance.  It  is  of  an  earthy 
aspect,  with  an  even  or  conchoidal  frac- 
ture, yellow  streak  oi  powder,  and  dull 
colours. 

CLAY  SLATE.  By  this  name  different 
rocks  have  been  designated.  1.  A  mica- 
ceous rock  is  so  named,  appearing  to  be 
mica-slate  in  a  state  of  extreme  division, 
the  scales  of  mica  having  gradually  be- 
come so  attenuated,  as  to  give  it  a  homo- 
geneous, glistening  appearance.  2.  A 
more  extensive  series  of  strata  of  clay- 
slate  is  found  associated  with  grey-wack.6 
and  other  rocks  of  a  less  crystalline  tex- 
ture than  the  primary,  and  occurs  in  the 
Cumbrian  and  the  Cambrian  Groups  of 
rocks. 

CLAYSTONE.  Compact  felspar,  with 
an  earthy  aspect,  conchoidal  uneven  frac- 
ture, and  of  various  colours.  It  is  often 
porphyritic,  containing  crystals  of  felspar. 
It  occurs  in  veins,  as  well  as  in  mountain 
masses. 

CLEAVAGE.  The  mechanical  divi- 
sion of  crystals,  by  which  the  inclination 
of  their  lamina  is  determined. 

Certain  rocks,  usually  called  slate- 
rocks,  admit  of  being  cleaved  into  an  in- 
definite number  of  thin  laminae  which 
are  parallel  to  each  other,  but  which  are 
generally  not  parallel  to  the  planes  of  the 


CLI 


CLO 


true  strata  or  layers  of  deposition.  The 
planes  of  cleavage  are,  therefore,  distin- 
guishable from  those  of  stratification. 

CLEA'VLANDITE.  A  mineral  for- 
merly ranked  among  felspars,  but  differ- 
ing in  this,  that  the  13  or  14  per  cent, 
of  potash  in  felspar  is  replaced  by  about 
10  per  cent,  of  soda  in  the  cleavland- 
ite.—  Ure. 

CLEF.  The  French  term  for  a  key. 
In  music,  it  is  a  symbol  placed  at  the 
beginning  of  the  staff  to  determine  the 
names  of  the  lines  and  spaces,  and  the 
character  of  each  note.  1.  The  treble 
clef  is  placed  on  the  second  line,  to  which 
it  gives  the  name  of  G.  2.  The  mean 
clef  gives  the  name  of  C  to  any  line  on 
■which  it  is  placed.  It  is  called  the  so- 
prano clef  when  placed  on  the  first  line; 
the  mezzo  soprano,  when  on  the  second; 
the  alto,  contratenor,  or  countertenor, 
when  on  the  third ;  and  the  tenor,  when 
on  the  fourth.  3.  The  base  clef  is  placed 
on  the  fourth  line,  to  which  it  gives  the 
name  of  F. 

CLEPSY'DRA  {K\e^viPa,  from  k\<?  ttto), 
to  steal,  v&up,  water).  A  water-clock, 
made  somewhat  like  our  sand-glasses, 
with  a  narrow  orifice  through  which  the 
water  trickled  slowly,  used  by  the  Greeks 
to  time  speeches  in  the  law-courts.  This 
instrument  was  commonly  employed  by 
astronomers  for  the  measurement  of 
time  before  the  invention  of  clocks  and 
watches. 

CLE'RIDjE.  A  family  of  Coleopterous 
insects,  of  the  section  Malacodermi, 
named  from  the  genus  Clerus. 

CLIMACTE'RIC  (KA^aK-rJ/p,  the  step 
of  a  ladder).  The  progression  of  the  life 
of  man.  It  is  usually  divided  into  pe- 
riods of  seven  years ;  the  ninth  period, 
or  63rd  year,  being  the  grand  climac- 
teric. 

CLI'MATE  (KX*'/xa,  inclination).  A 
term  applied  in  its  popular  sense  to  the 
state  of  the  air,  in  order  to  express  the 
particular  combination  of  temperature 
and  moisture,  which  exists  in  the  atmo- 
sphere of  any  given  country. 

In  its  geographical  and  technical  appli- 
cation, Climate,  or  Clime,  denotes  an 
imaginary  narrow  belt  of  the  globe,  paral- 
lel to  the  equator;  and  is  so  called  be- 
cause the  difference  of  climates  depends 
on  the  inclination,  or  obliquity  of  the 
sphere.  The  belts  constituting  the  seve- 
ral climates  are  small,  depending  on  the 
average  length  of  the  longest  day  :  that 
of  each  increasing  by  half  an  hour,  from 
the  equator  to  the  polar  circles,  when  the 
81 


climates  are  counted  by  months,  till  they 
reach  the  poles. 

CLI'MAX  UMjuaf ,  a  ladder  or  stair- 
case). In  rhetoric,  a  gradual  ascent  from 
weaker  to  stronger  expressions,  as  in  the 
celebrated  M  gradatio  "  of  Cicero, — abiit, 
excessit,  evasit,  erupit. 

CLINA'NTHIUM  (kAu/o,  to  incline, 
avOos,  a  flower).  A  term  applied  by  some 
botanical  writers  to  the  receptacle  of  com- 
positae  which  is  not  fleshy,  but  is  sur- 
rounded by  an  involucrum.  By  other 
writers,  this  part  is  called  thalamus  and 
phoranthium. 

CLINKER.  Black  oxide  of  iron,  or 
the  oxidum  ferroso-ferricum  of  Berzelius. 
It  is  always  formed  when  iron  is  heated  to 
redness  in  the  open  air,  and  is  therefore 
readily  obtained  at  the  blacksmith's 
forge. 

CLINKSTONE.  Ahardfelspathicrock, 
named  from  the  sharp  noise  which  it 
emits  when  struck  with  the  hammer; 
its  fracture  is  splintery  and  conchoidal, 
its  lustre  glistening,  its  colours  various, 
often  with  veins  of  jasper. 

CLINO'METER  {k\Lvu>,  to  incline, 
H^rpov,  a  measure).  A  quadrant  adapted 
for  showing  the  inclination  of  strata  in 
geological  operations. 

CLIO'NIDjE.  The  Clio  tribe;  a  fa- 
mily of  naked  marine  mollusca,  the  first 
order  of  Cuvier's  Pteropods. 

CLOA'CA  (a  sewer).  A  receptacle 
observed  in  the  monotremata,  in  birds, 
in  reptiles,  and  in  many  fishes,  which 
receives  the  faeces  and  the  urine,  to- 
gether with  the  semen  of  the  male,  and 
the  ovum  of  the  female. 

CLOCK.  A  well  known  machine  for 
measuring  time,  regulated  by  the  uni- 
form motion  of  a  pendulum.  Common 
clocks  are  made  to  show  mean  solar 
time,  but  those  used  at  observatories,  for 
the  purpose  of  observing  the  time  of  the 
stars  transiting  the  meridian,  show  side- 
real time. 

CLOUDS.  Masses  of  visible  aqueous 
vapour,  which  float  in  the  sky,  or  drift 
through  it  with  the  wind,  at  different 
elevations,  assuming  every  variety  of 
colour  and  form.  They  have  been  clas- 
sified by  Howard  under  three  primary 
forms,  and  four  modifications. 

1.  Primary  Forms.  These  are  the  cir- 
rus, or  curl-cloud,  composed  of  fibrous 
stripes,  which  are  parallel,  flexuous,  or 
diverging,  and  extensible  in  all  direc- 
tions ;  the  cumulus,  or  stacken-cloud, 
heaped  together  in  convex  or  conical 
masses,  and  increasing  upwards  from  a 
E5 


CO  A 


COC 


horizontal  base ;  and  the  stratus,  or  fall- 
cloud,  spreading  horizontally  in  a  con- 
tinuous layer,  and  increasing  from  below. 
The  first  of  these  forms  is  confined  chiefly 
to  the  higher  regions  of  the  atmosphere ; 
the  second  occupies  a  lower,  but  still  an 
elevated  station  ;  the  third  usually  rests 
upon  the  surface  of  the  earth,  constitut- 
ing mists, 

2.  Modifications.  Of  the  four  modified 
forms  of  clouds,  two  are  intermediate, 
and  two  are  composite.  1.  The  inter- 
mediate forms  are  the  cirro-cumulus, 
consisting  of  small,  roundish,  and  well- 
defined  masses  in  close  horizontal  ar- 
rangement; and  the  cirro-stratus,  like- 
wise in  small  and  rounded  masses,  but 
attenuated  towards  a  part,  or  towards  the 
whole,  of  their  circumference.  2.  The 
composite  forms  are  the  cumulo-stratus, 
made  up  of  the  cirro-stratus  blended  with 
the  cumulus,  the  cirro-stratus  being 
either  intermingled  with  the  larger 
masses  of  the  cumulus,  or  widely  en- 
larging the  cumulous  base ;  and  the 
cumulo-cirro-stratus,  nimbus,  or  rain- 
cloud,  being  a  horizontal  layer  of  aque- 
ous vapour,  over  which  clouds  of  the 
cirrous  form  are  spread,  while  other 
clouds  of  the  cumulous  form  enter  it 
laterally  and  from  beneath. 

CLOVES.  A  technical  appellation  of 
the  small  bulbs  developed  at  the  base  of 
a  parent  bulb. 

CLUPE'IDJL  The  Herring  tribe;  a 
family  of  Malacopterygious  or  soft-spined 
fishes,  named  from  the  genus  Clupea, 
and  differing  from  the  Salmonidae  in  the 
absence  of  fatty  matter  in  the  dorsal 
fin. 

CLY'PEIFORM  (clypeus,  a  shield, 
forma,  shape).  Shield-shaped;  a  term 
applied  to  the  large  prothorax  in  beetles. 
Clypeate  is  a  similar  term,  applied,  in 
Botany,  to  the  scales  found  on  the  leaves 
of  certain  plants,  and  synonymous  with 
scutate  or  scutiform. 

COAGULA'TION  {con  and  agere,  to 
bring  together).  A  term  formerly  syn- 
onymous with  crystallization,  but  now 
applied  to  the  partial  solidification  of  a 
fluid  body  by  exposure  to  cold,  or  by  the 
addition  of  some  agent.  Spontaneous 
coagulation  denotes  the  cohesion  of  the 
particles  of  the  blood,  of  some  effused 
fluids,  &c.  Induced  coagulation  denotes 
the  effect  produced  upon  albumen  by 
heat,  alcohol,  acids,  rennet,  &c. 

COAL.  A  combustible  mineral,  con- 
sisting of  bitumen,  carbon,  and  earthy 
matter,   in    various    proportions.      The 


varieties  are  easily  recognized,  being 
hard,  black,  brittle,  and  laminated.  Peat, 
which  consists  of  partially  decomposed 
roots  and  stems  of  various  plants,  may 
be  considered  as  forming  one  extremity 
of  the  series,  which  terminates  in  the 
other  with  glance  coal  or  anthracite. 

COAL  FORMATION.  A  term  gene- 
rally employed  as  synonymous  with  that 
of  coal  measures  or  carboniferous  group. 
This  very  comprehensive  group  embraces 
not  only  the  coal  strata,  and  the  beds  of 
sandstone,  limestone,  and  others  alter- 
nating with  it,  but  the  mountain  lime- 
stone and  the  old  red  sandstone,  on  which 
the  proper  coal  group  may  be  said  to 
rest. 

Werner's  Coal  Formations.  The  first 
or  oldest  is  called  the  independent  forma- 
tion, from  the  individual  depositions 
composing  it  being  independent  of,  and 
unconnected  with,  each  other.  The  se- 
cond occurs  in  the  newest  floetz-trap 
formation  ;  the  third  in  alluvial  land.  A 
fourth  would  comprehend  peat  and  other 
similar  substances. 

COAL  GAS.  A  gas  procured  from 
coal,  when  subjected  in  close  vessels  to 
a  red  heat,  and  employed  for  illumi- 
nation. 

COA'RCTATE  (coarcto,  to  compress). 
An  epithet  applied  to  the  pupa  of  an  in- 
sect, which  is  enclosed  in  a  case,  giving 
no  indication  of  the  parts  contained  in  it. 

COARSE  COAL.  A  sub-species  of 
black  coal,  occurring  in  the  German  coal 
formations.  To  this  head  is  also  referred 
the  soot  coal,  which  occurs  together  with 
slate-coal,  in  the  Forth  district,  &c. 

COATING.  Loricalion.  A  method  of 
securing  or  repairing  retorts  used  in  dis- 
tillation. Coatings  are  made  of  marly 
earth,  kneaded  with  fresh  horse-dung, 
slaked  lime,  and  linseed  oil,  &c. 

COBALT  (Cobalus,  the  demon  of 
mines).  A  metal,  found  chiefly  in  com- 
bination with  arsenic,  as  arsenical  co- 
balt; or  with  sulphur  and  arsenic,  as 
grey  cobalt  ore.  These  ores  are  em- 
ployed to  give  the  blue  colour  of  por- 
celain and  stone- ware. 

CO'BALUS.  The  demon  of  mines, 
which  obstructed  and  destroyed  the 
miners.  The  Germans  formerly  used  a 
form  of  prayer  for  the  expulsion  of  the 
fiend.  The  ores  of  cobalt,  being  at  first 
mysterious  and  intractable,  received  their 
name  from  this  personage. 

CO'CCIDiE  (coccus,  the  cochineal  in- 
sect). The  Scale  insects ;  the  single 
family  of  the  monomerous  Homoptera, 


COH 


COL 


remarkable  for  the  production  of  cochi- 
neal and  other  valuable  dyes. 

CO'CCOLITE  (ko/ckov,  a  kernel,  Xi'0or, 
a  stone).  A  green  mineral,  occurring  in 
loosely  aggregated  concretions,  together 
with  granular  limestone  and  other  sub- 
stances, in  beds  subordinate  to  the  trap 
formation. 

COCCOO'N  (kokkop,  a  berry  or  kernel). 
The  silken  case  which  certain  insects 
spin  for  a  covering  during  the  period  of 
their  metamorphosis,  as  that  of  the  silk- 
worm when  passing  into  the  pupa  state. 

CO'CCUS  (kokkop,  a  kernel).  A  term 
applied,  in  Botany,  to  a  pericarp  of  dry, 
elastic  pieces,  or  coccules,  as  in  Euphor- 
bia. In  this  plant,  the  cocci  are  three  in 
number,  and  the  fruit,  generally  called  a 
regma,  is  therefore  also  termed  a  tricoc- 
cous  capsule. 

COCHINE'AL.  The  technical  name  of 
the  coccus  cacti,  a  homopterous  insect, 
brought  from  Mexico,  and  employed  by 
dyers.  Cochinilin  is  a  colouring  matter 
obtained  from  cochineal,  and  is  a  consti- 
tuent of  carmine.  The  term  granilla  is 
applied  to  very  small  insects  of  this  kind, 
from  their  resemblance  to  little  grains. 

CO'CHLEATE  (cochlea,  from  K6xXof, 
a  conch).  Shell-shaped;  shortly  spiral, 
like  a  snail's  shell,  as  the  legume  of 
medicago  falcata. 

COCFNIC  ACID.  Cocostearic  acid. 
The  crystallizable  acid  of  the  butter  of 
the  cocoa  nut. 

CO'DA  (coda,  Ital.,  a  tail).  In  Music, 
a  passage  of  variable  length  at  the  end 
of  a  movement  which  follows  a  length- 
ened perfect  cadence. 

CO'DEINE  (K<a8eia,  a  poppy  head). 
One  of  the  vegetable  bases  of  opium. 

CO-EFFICIENT.  A  term  applied,  in 
Algebra,  to  the  number,  negative  or 
positive,  which  is  prefixed  to  any  alge- 
braical quantity,  to  show  how  often  it  is 
to  be  taken.  It  is  that  factor  which  is  a 
number,  as  3a,  or  5a2c. 

CCELELMI'NTHA  (koIXo?,  hollow, 
eX/uti/p,  a  worm).  Intestinal  worms  which 
are  hollow,  and  contain  an  alimentary 
tube  in  the  cavity  of  the  body.  These 
are  the  cavitary  intestinal  worms  of  Cu- 
vier,  the  nematoidea  of  Rudolphi. 

CCENO'BIO  (Kotvofitos,  living  in  com- 
munion with  others).  The  term  by 
which  Mirbel  designates  the  fruit  of  the 
Labiatse.  It  differs  from  the  carcerule 
merely  in  the  low  insertion  of  the  style 
into  the  ovaria,  and  the  distinctness  of 
the  latter. 

COHE'SION  (cohcereo,  to  stick  to- 
83 


gether).  That  relation  among  the  com- 
ponent parts  of  a  body,  by  which  they 
cohere,  or  are  kept  together.  The  un- 
known principle  by  which  particles  co- 
here is  called  the  attraction  of  cohesion. 
On  the  degree  of  this  force  depend  the 
aggregate  forms  of  matter,  distinguished 
as  the  solid,  the  liquid,  and  the  gaseous. 

COHOBA'TION.  The  continuous  re- 
distillation of  a  liquid  from  the  same 
materials,  or  from  a  fresh  parcel  of  the 
same  materials. 

COKE.    The  residue  of  coal,  when  the  1     | 


volatile  matters  have  been  driven  off. 

CO'LCOTHAR.  The  brown-red  oxide 
of  iron,  which  remains  after  the  distilla-    y  / 

tion  of  the  acid  from  sulphate  of  iron. 
It  is  used  for  polishing  glass,  &c,  under    .       /    >' 
the  name  of  crocus,  or  crocus  martis.        c     *  V r  r* 

COLEOPHY'LLUM  (KoXeop,  a  sheath, 
<pv\\ov,  a  leaf).  Coleoptile.  In  Botany, 
the  sheath  within  which  the  young  leaves 
of  monocotyledons  are  developed.  By 
the  term  coleorrhiza  (pi£a,  root),  Mirbel 
designates  the  sheath  at  the  base  of  the 
radicle  of  monocotyledons. 

COLEO'PTERA  (KoXeoc,  a  sheath, 
nrepov,  a  wing).  Sheath-winged  insects ; 
an  order  of  insects  which  have  four 
wings,  the  upper  pair  being  crustaceous, 
and  forming  a  sheath,  or  shield  (elytron), 
to  the  lower  pair,  as  in  the  beetle.  The 
order  has  been  distinguished  by  Latreille, 
with  reference  to  the  number  of  joints 
in  the  tarsi,  or  divisions  of  the  foot,  into 
the  pentamera,  heteromera,  tetramera, 
and  trim  era. 

COLLECTOR,  ELECTRICAL.  The 
upper  plate  or  disc  of  a  condenser,  em- 
ployed for  collecting  electricity. 

COLLECTORS.  A  term  applied,  in 
Botany,  to  those  hairs  with  which  the 
style  of  Compositae,  Campanulaceae,  and 
others,  is  often  densely  covered,  and 
which  seem  intended  as  brushes  to  col- 
lect and  clear  the  pollen  out  of  the  cells 
of  the  anthers. 

COLLE'NCHYMA  (K6\\a,  glue,  e'y 
xvfxa,  infusion).  A  term  applied  by 
Link  to  the  cellular  substance  in  which 
the  pollen  of  Orchidaceous  and  Ascle- 
piadaceous  plants  is  generated.  It  is 
supposed  to  constitute  the  appendage  of 
the  pollen-masses  of  the  former  of  these 
tribes  of  plants. 

COLLIMA'TION,  LINE  OF  (collimo, 
for  collineo,  to  level,  or  aim  in  a  right 
line).  The  line  of  sight  in  an  astronomi- 
cal or  geodesical  instrument.  The  central 
line  of  a  telescope,  or  that  which  joins 
the  centres  of  its  object-glass  and  its  eye- 
E6 


COL 


COL 


glass,  is  called  in  Astronomy  its  line  of 
collimation.  The  difference  between  the 
existing  and  the  required  positions  of  an 
instrument  is  called  the  error  of  collima- 
tion. This  error  is  determined,  without 
reversal  of  the  instrument,  by  means  of 
a  contrivance  called  a  collimator. 

CO'LLUM.  The  neck.  This  term  de- 
notes, in  Botany,  that  portion  of  the  axis 
of  growth  where  the  stem  and  the  root 
diverge :  by  Grew  it  was  termed  coarc- 
ture ;  by  Lamarck,  vital  knot. 

CO'LOPHONITE.  A  mineral  with  a 
resinous  fracture,  found  in  magnetic 
iron-stone  in  Norway,  identical  with 
the  resinous  garnet  of  Haiiy  and  Jame- 
son. 

CO'LOPHONY.  Resin  of  turpentine ; 
the  residue  of  common  turpentine,  after 
its  essence  has  been  removed  by  distilla- 
tion. It  is  not  a  homogeneous  product, 
but  has  been  divided  into  two  different 
resins,  named  by  Unverdorben  the  sylvic 
and  pinic  acids. 

COLOURS.  A  general  term  for  those 
modifications  of  light,  whether  direct  or 
reflected  from  other  bodies,  by  which  the 
sight  is  affected  with  distinct  sensations. 
The  colour  of  a  body  is  designated  by  the 
particular  species  of  light  reflected  from 
its  surface,  which  may  therefore  be  called 
the  objective  colour,  or  that  which  is  per- 
manent to  the  body. 

1.  Prismatic  Colours.  Colours  pro- 
duced by  transmitting  white  light  through 
colourless  prismatic  bodies.  The  light 
undergoes  refraction,  and  is  dispersed, 
presenting  the  phenomenon  of  the  solar 
or  prismatic  spectrum.  The  colours  ex- 
hibited by  opaque  or  non-luminous  sub- 
stances, when  they  either  reflect  or  trans- 
mit white  light,  are  called  natural 
colours. 

2.  Primary  Colours.  These  are  red, 
orange,  yellow,  green,  blue,  and  violet, 
being  the  different  colours  into  which  a 
solar  ray  of  light  may  be  decomposed. 
White  is,  therefore,  a  compound  of  these 
colours,  and  black  is  the  absence  of  all 
colours.  The  primary  colours  are  not 
decomposable,  but  have  uniform  refrac- 
tion ;  hence  they  were  termed  by  Newton, 
homogeneous  colours,  to  distinguish  them 
from  common  or  white  light,  which  he 
called  compound  or  heterogeneous. 

3.  Secondary  Colours.  According  to 
Brewster,  there  are  only  three  primary 
or  fundamental  colours;  viz.  red,  yellow, 
and  blue;  the  other  three,  viz.  orange, 
green,  and  violet,  being  produced  by 
combination  of  the  former,  and  therefore 

84 


properly  termed  secondary  or  compound 
colours. 

4.  Complementary  Colour.  That  colour 
with  which  each  of  the  prismatic  colours 
will  combine,  and  form  white  light.  The 
complementary  colour  to  each  of  the 
three  primaries,  is  the  compound  colour 
obtained  by  combining  the  other  two  pri- 
maries ;  and,  for  each  of  the  secondaries, 
that  primary  one  which  does  not  enter 
into  its  composition. 

5.  Accidental  Colours.  A  series  of 
optical  phenomena,  commonly  called 
ocular  spectra.  If  the  eye  be  steadily 
directed,  for  some  time,  to  a  white  wafer 
upon  a  dark  ground,  and  be  then  turned 
aside,  a  spectrum  of  the  wafer  will  be 
perceived,  with  the  colours  reversed :  the 
wafer  will  appear  dark,  the  ground  white. 
If  the  wafer  be  red,  its  spectrum  will  be 
bluish-green  ;  if  orange,  blue  ;  if  blue, 
orange-red,  &c.  Darwin  classes  the 
spectra  under  the  heads  of  direct  and  re- 
verse, the  former  depending  on  the  per- 
manence of  the  impression,  the  latter 
upon  exhaustion.  Accidental  colours 
are  sometimes  called  subjective  or  phy- 
siological, to  distinguish  them  from  the 
permanent  or  objective  colours. 

6.  Entoptic  Colours.  A  term  applied 
by  Seebeck  to  the  spectra  obtained  by 
transmitting  polarized  light  through  a 
crystal  cut  at  right  angles  to  its  axis,  the 
light  being  made  to  pass  in  the  direction 
of  the  axis.  The  phenomena  consist  of 
concentric  rings  of  various  colours,  re- 
sembling Newton's  prismatic  rings,  and 
intercepted  in  the  middle  by  a  rect- 
angular cross. 

COLOURED  RINGS.  Luminous 
rings  produced  by  interference  of  the 
rays  of  light,  or  by  electro-chemical  de- 
composition. Of  the  former  kind  are 
Newton's  coloured  rings,  which  may  be 
produced  by  pressing  a  watch-glass  upon 
a  piece  of  plate-glass ;  the  rings  will  ap- 
pear about  their  point  of  contact,  of  the 
same  colour  as  the  incident  rays,  if  the 
light  be  homogeneous.  Of  the  second 
kind  are  NobilVs  rings,  which  are  pro- 
duced when  a  feeble  current  of  electricity 
is  directed  upon  a  polished  metallic  plate, 
this  plate  being  used  as  an  electrode, 
and  immersed  in  an  electrolytic  fluid; 
the  rings  will  then  appear  upon  the 
plate. 

COLOURING  MATTER.  Colouring 
principles  found  in  vegetable  substances, 
and  employed  in  dyeing.  Colours  are 
termed  substantive,  when  they  adhere  to 
the  cloth  without  the  intervention  of  a 


COL 


COM 


base ;  adjective,  when  they  require  a  base 
for  that  purpose. 

COLPE'NCHYMA  (koXtto?,  a  loose 
fold,  eyxvua,  infusion).  A  term  applied 
by  Morren  to  the  sinuous  form  of  the 
parenchyma  of  plants. 

COLUBE'RIDjE  {coluber,  a  snake). 
A  family  of  Ophidian  reptiles,  including 
the  Boa  Constrictors  of  the  New  World 
and  the  Pythons  of  the  Old,  and  other 
non-venomous  snakes  not  belonging  to 
the  other  families  of  the  order. 

COLU'MB A  NO'ACHI.  Noah's  Dove ; 
a  modern  southern  constellation,  consist- 
ing of  ten  stars,  close  to  the  hinder  feet 
of  Canis  Major. 

COLUMBE'LLIN^.  Dove-shells;  a 
sub-family  of  the  Strombidce,  or  Wing- 
shells,  named  from  the  typical  genus 
columbella  ;  these  are  small  shells,  with 
sharp-pointed  spires ;  the  outer  lip  is 
thick,  turned  inwards,  more  or  less 
toothed  on  its  edge,  and  gibbous  above ; 
there  are  also  tuberculated  teeth  at  the 
base  of  the  inner  lip,  but  no  regular 
plaits. 

COLU'MBID^E  {columba,  a  dove  or 
pigeon).  The  Pigeon  tribe;  a  group 
of  the  Rasores,  or  Scratching  birds, 
chasacterized  by  the  double  dilatation 
of  the  crop,  and  their  habit  of  feeding 
their  young  with  food  disgorged  from 
this  receptacle.  Macgillivray  considers 
that  the  Pigeons  belong  neither  to  the 
Rasores  nor  to  the  Insessores,  but  appear 
to  form  an  order  separated  by  well- 
defined  limits.     See  Gemitrices. 

COLUMBIUM.  Another  name  for  the 
metal  tantalum,  from  its  having  been 
brought,  as  it  is  said,  from  Massachusetts 
in  North  America.  By  fusion  of  its  ore, 
or  columbite,  an  acid  is  obtained,  called 
columbic  acid. 

COLUME'LLA  (dim.  of  columna,  a 
pillar).  A  little  pillar  ;  the  internal  sup- 
port of  most  spiral  shells,  round  which 
the  whorls  are  convoluted.  In  botany, 
it  denotes  the  axis  from  which  the  valves 
of  a  fruit  separate,  on  dehiscence ;  the 
axis  which  occupies  the  centre  of  the 
sporangium  of  mosses,  &c. 

COLU'MNA.  A  column  ;  a  term  ap- 
plied, in  botany,  to  the  solid  body  formed 
by  a  combination  of  the  filaments,  as  in 
stapelia,  rafflesia,  &c. 

COLURES  (xoWpop ,  a  truncated  tail). 
An  old  term  employed  in  Astronomy  to 
designate  two  great  circles  of  the  sphere, 
which  pass,  the  equinoctial  colure  through 
the  equinoctial  points  and  the  poles  of 
the  equator,  the  solstitial  colure  through 
85 


the  solstitial  points  and  the  poles  of  the 
ecliptic  and  of  the  equator. 

COLY'MBIDuE  {colymbus,  a  diver). 
The  Divers ;  a  small  family  of  the  Nata- 
tores,  or  Swimming  birds,  characterized 
by  remarkably  short  wings,  and  a  length- 
ened, strong,  straight  bill. 

CO'MA.  Literally,  hair ;  and  hence 
applied  to  the  assemblage  of  branches 
which  forms  the  head  of  a  forest  tree. 
Cyma  is  sometimes  employed,  though 
erroneously,  to  express  the  same  thing. 

COMA  BERENICES.  Berenice's 
Hair ;  a  modern  northern  constellation, 
consisting  of  forty-three  stars,  and  named 
after  the  wife  of  Ptolemy  Euergetes. 

COMBINATIONS.  In  Algebra,  the 
combinations  of  any  number  of  quan- 
tities are  the  different  sets  which  can  be 
made  of  them,  taking  a  certain  number 
together,  without  regard  to  the  order  in 
which  they  are  placed.  Thus,  the  com- 
binations of  a,  b,  c,  d,  taken  3  together, 
are  abc,  abd,  acd,  bed. 

COMBINATION,  CHEMICAL.  The 
union  of  the  particles  of  different  sub- 
stances, by  chemical  attraction,  in  form- 
ing new  compounds.  See  Atomic  Weights. 

COMBINING  QUANTITY.  Various 
terms  have  been  proposed  for  expressing 
the  combining  quantities  of  elementary 
and  compound  substances,  and  all  ob- 
jectionable. Atom  is  not  only  hypotheti- 
cal, but  often  inapplicable,  as  when  half 
atoms  occur.  Equivalent  is  only  expres- 
sive when  comparison  with  a  correlative 
equivalent  is  directly  implied.  Proportion 
means  similitude  of  ratios.  Proportional 
is  one  of  the  terms  of  a  proportion. 
Combining  quantity  or  weight  is  some- 
times expressive ;  but,  besides  being 
unwieldy,  it  is  not  always  applicable. 
Dr.  Donovan  adds,  the  word  dose  is 
universally  employed  to  designate  a  de- 
terminate or  definite  quantity  of  a  thing 
given;  it  has  the  quality  of  involving 
nothing  beyond  a  fact,  and  can  often  be 
used  with  advantage. 

COMBU'STIBLE.  A  body  which,  in 
rapid  union  with  other  bodies,  disengages 
heat  and  light.  Simple  combustibles  are 
hydrogen,  carbon,  boron,  sulphur,  phos- 
phorus, nitrogen,  and  the  metals ;  com- 
pound combustibles  are  the  hydrurets, 
carburets,  sulphurets,  phosphorets,  me- 
tallic alloys,  and  organic  products. 

COMBU'STION  {comburo,  to  burn  to- 
gether). The  act  of  burning  ;  a  pheno- 
menon produced  by  the  chemical  combi- 
nation of  two  substances,  attended  by  the 
development  of  heat  and  light ;  it  usually 


COM 


COM 


takes  place  in  the  combination  of  oxygen, 
but,  in  a  few  cases,  in  that  of  chlorine 
and  of  sulphur.  Bodies  which  are  con- 
sidered as  the  causes  of  this  phenomenon 
are  called  supporters  of  combustion,  whilst 
the  radicals  which  combine  with  them 
are  called  combustibles. 

1.  Combustion,  Invisible.  A  term  ap- 
plied by  Davy  to  those  phenomena  of 
combustion  which  are  effected  without 
the  disengagement  of  light,  as  when 
oxygen  and  hydrogen,  confined  in  tubes, 
are  carefully  exposed  to  a  high  tempe- 
rature. 

2.  Combustion,  Spontaneous.  This  is 
said  to  occur  in  the  human  body ;  and  it 
does  occur  when  masses  of  vegetables,  as 
damp  hay,  or  oily  cotton,  are  heaped  to- 
gether. There  are  also  cases  on  record 
of  the  spontaneous  ignition  of  charcoal, 
both  dry  and  moist. 

COME'NIC  ACID.  A  bibasic  acid, 
formed  from  the  meconic  acid,  of  which 
it  is  a  congener.  It  is  decomposed  by 
heat,  and  another  congener  is  produced, 
viz.  pyromeconic  acid. 

CO'MET  (KOfxtiTw,  from  Ko/itj,  hair). 
Literally,  a  hairy  star.  A  celestial  body 
which  occasionally  traverses  our  system 
in  a  very  eccentric  orbit,  without  appear- 
ing to  form  a  part  of  it.  Its  central 
point,  which  is  more  or  less  lustrous,  is 
called  its  nucleus.  The  nebulous  light 
surrounding  the  nucleus,  is  the  chevelure 
or  hair.  The  luminous  train  by  which 
most  comets  are  accompanied  was  for- 
merly called  beard  or  tail,  accordingly  as 
it  preceded  or  followed  the  comet  in  its 
course.  At  present  it  is  called  tail,  what- 
ever be  its  position.  Lastly,  the  nucleus 
and  the  chevelure  together  constitute 
the  head  of  the  comet. 

COMETA'RIUM.  A  machine  show- 
ing the  motion  of  a  comet  about  the 
sun  ;  any  instrument  capable  of  describ- 
ing an  elongated  ellipse. 

COMMA  (K<5/x/Lia,  that  which  is  struck). 
The  smallest  interval  in  music,  being  the 
ninth  part  of  a  major  tone. 

COMMISSURAL  (committo,  to  solder). 
Belonging  to  a  line  or  part  by  which 
other  parts  are  connected  together.  The 
connecting  line  is  the  commissure. 

COMMON  MEASURE.  In  Arith- 
metic, a  number  which  divides  two  or 
more  other  numbers  without  leaving  a 
remainder. 

COMMON  TERM.  A  logical  expres- 
sion for  a  term  which  is  applicable  in  the 
same  sense  to  more  than  one  individual 
object.    Common  terms,    therefore,    are 


called  "predicables,"  that  is,  affirmatively 
predicable,  from  their  capability  of  being 
affirmed  of  others.     See  Singular  Term. 

COMMUTATOR  or  GY'ROTROPE. 
An  apparatus  included  in  the  circuit 
between  the  battery  and  the  electro- 
magnetic apparatus,  for  the  purpose  of 
reversing  the  direction  of  the  current 
without  the  necessity  of  changing  the 
arrangement  of  the  conductors  from  the 
poles. 

COMPASS,  MARINER'S.  A  mag- 
netic needle,  balanced  on  a  pivot,  for 
pointing  out  the  true  direction  of  north 
and  south.  In  the  mariner's  compass, 
the  circle  traversed  by  the  point  of  the 
needle  is  marked  off  into  32  rhumbs  or 
points;  in  the  azimuth  compass  the  same 
circle  is  divided  into  360°. 

COMPATIBLE  TERMS.  In  Logic, 
terms  expressive  of  two  views  which 
may  be  taken  of  the  same  object  at  the 
same  time,  as  to  be  "white  and  cold." 
See  Opposite  terms. 

COMPENSATION  PENDULUM.  A 
pendulum  made  of  different  substances, 
so  combined  that  the  effects  of*  heat 
counteract  each  other,  and  the  length  of 
the  rod  remains  unaltered. 

CO'MPLEMENT  {compleo,  to  fill  up). 
A  magnitude  which,  taken  with  another, 
makes  up  a  given  magnitude.  The  com- 
plement of  an  arc  or  angle  is  what  is 
required  to  complete  a  quadrant  or  right 
angle.  The  arithmetical  complement  of 
a  number  is  the  number  by  which  it  falls 
short  of  the  next  higher  decimal  denomi- 
nation. The  complement  of  a  logarithm 
is  the  number  by  which  a  logarithm  falls 
short  of  10.  The  complement  of  altitude 
is  the  zenith  distance ;  that  of  latitude, 
the  polaoiirtance. 

COMPOSITE.  The  Synantherous 
tribe  of  dicotyledonous  plants.  Herba- 
ceous plants  or  shrubs  with  leaves  alter- 
nate or  opposite ;  flowers  (called  florets) 
unisexual  or  hermaphrodite,  collected  in 
dense  heads  upon  a  common  receptacle, 
surrounded  by  an  involucrum  ;  florets 
monopetalous  ;  anthers  syngenesious  ; 
ovarium  one-celled ;  fruit  a  dry,  inde- 
hiscent  pericarp,  termed  achenium  or 
cypsela. 

COMPOSITION  {compono,  to  put 
together).  A  technical  term  used  by 
geometers  to  signify  one  of  the  ways  of 
changing  the  order  or  magnitude  of  pro- 
portionals, so  that  they  continue  still  to 
be  proportionals.  Thus  of  four  propor- 
tionals, the  first,  together  with  the 
second,  is  to  the  s<  cond,  as  the  third, 


CON 


CON 


together  with  the  fourth,  is  to  the  fourth. 
See  Force. 

COMPOSITION,  FALLACY  OF.  A 
logical  fallacy,  in  which  the  middle  terra 
is  used  in  one  premiss  collectively,  in  the 
other  distributively.  The  form  in  which 
it  is  most  usually  employed,  is  to  esta- 
blish some  truth,  separately,  concerning 
each  member  of  a  certain  class,  and 
thence  to  infer  the  same  of  the  whole 
collectively.  Thus,  it  may  be  argued  that, 
because  it  is  not  very  improbable  that 
a  person  may  throw  sixes  in  any  one  out 
of  a  hundred  throws,  therefore  it  is  no 
more  improbable  that  he  may  throw 
sixes  a  hundred  times  running.    Whately. 

COMPOUNDS.  The  following  terms 
are  employed  in  designating  compounds : 

1.  Binary,  ternary,  quaternary.  These 
terms  refer  to  the  number  of  elements  or 
proximate  principles— two,  three,  or  four 
— which  exist  in  a  compound.  The  binary 
compounds  of  oxygen,  chlorine,  iodine, 
bromine,  and  fluorine,  which  are  not 
acid,  terminate  in  ide,  as  oxide,  chloride, 
&c. ;  those  of  all  other  substances  termi- 
nate in  uret,  as  hydruret  of  carbon,  sul- 
phuret  of  iron,  &c. 

2.  Bis,  ter,  quater.  These  are  Latin 
numerals,  indicating  the  number  of  aioms 
of  acid,  which  are  combined  with  one  of 
the  base  in  a  compound,  as  fo'-sulphate  of 
soda,  &c. 

3.  Dis,  iris,  tetrakis.  These  are  Greek 
numerals,  indicating  the  number  of  atoms 
of  base,  which  are  combined  with  one  of 
the  acid  in  a  compound,  as  de-chromate 
of  lead,  &c.  No  prefix  is  used  when  the 
compound  consists  of  one  atom  of  each 
ingredient.  But  there  are  many  excep- 
tions to  these  rules  :  protoxide  and  deut- 
oxide  are  frequently  used  for  oxide  and 
bin-oxide  respectively. 

COMPRESSIBILITY  (comprimo,  to 
compress).  A  property  of  masses  of  mat- 
ter, by  which  their  particles  are  capable 
of  being  brought  nearer  together.  Bodies 
which  recover  their  former  bulk  on  re- 
moval of  the  compressing  cause,  are 
called  elastic. 

CO'MPTONITE.  A  mineral  found  in 
drusy  cavities,  in  ejected  masses,  on 
Mount  Vesuvius ;  first  brought  to  this 
country  by  Lord  Compton,  in  1818. 

CONCENTRATION.  The  strengthen- 
ing of  solutions  or  mixtures  by  evapora- 
tion of  their  watery  parts. 

CONCE'NTRIC.     Having    the    same 

centre,   as  applied  to   circles  which  are 

described  about  the  same  point,  to  the 

striae  of  bivalves  which  run  parallel  to 

87 


the  margin,  &c.  The  concentric  theory 
is  the  theory  of  epicycles,  as  opposed  to 
the  eccentric  theory.     See  Epicycle. 

CONCEPTA'CULUM.  Literally,  a 
receptacle ;  a  term  applied,  in  Botany,  to 
a  species  of  compound  fruit,  which  is  two- 
celled,  many-seeded,  superior,  separating 
into  two  portions,  the  seeds  of  which 
detach  themselves  from  their  placenta, 
and  lie  loose  in  the  cavity  of  each  cell. 
This  fruit  occurs  in  Asclepias,  and  is  also 
called  the  double  follicle. 

CONCH A'CEA  {Ko^Xn,  a  shell).  A 
family  of  conchiferous  molluscs,  in  De 
Blainville's  arrangement,  corresponding 
with  Cuvier's  Cardiaceae,  or  the  Cockle 
tribe.     See  Cardiacece. 

CONCHPFERA  {concha,  a  shell,  fero, 
to  carry).  A  class  of  the  Mollusca,  com- 
prising acephalous  aquatic  animals,  co- 
vered with  a  bivalve  or  multivalve  shell. 
There  are  two  orders,  viz. — 

1.  Monomyaria,  in  which  the  shells 
are  narrow  longitudinally,  and  have  but 
one  muscular  impression  on  the  valve, 
as  in  the  spondylus. 

2.  Dimyaria,  in  which  the  shell  is  ex- 
tended longitudinally,  and  has  two  mus- 
cular impressions  on  the  valve,  as  in  the 
area  barbata. 

CONCHOID  (noyxoeiSijs,  resembling 
a  shell).  The  designation  of  a  curve, 
employed  by  Nicomedes  for  finding  the 
two  mean  proportionals,  and  the  dupli- 
cation of  the  cube. 

CONCH  O'LOGY  (rfy%*,  a  shell,  A6709, 
a  description).  The  "  art "  of  arranging 
the  shells  of  testaceous  animals,  without 
reference  to  the  animals  which  they  con- 
tain.    See  Malacology. 

CONCLUSION.  In  Logic,  the  propo- 
sition which  is  inferred  from  the  premises 
of  an  argument. 

CO'NCORD.  A  term  applied  in  Music 
to  two  combined  sounds  which  are  uni- 
versally agreeable  to  the  ear.  The  8th, 
or  octave,  and  the  5th  are  called  perfect 
concords,  because  as  concords  they  are 
not  liable  to  alteration  by  flats  or  sharps ; 
the  3rd  and  6th  are  termed  imperfect  con- 
cords, because  alterable. 

CONCRETE.  A  term  denoting  a  qua- 
lity accompanied  with  its  particular  sub- 
ject, as  opposed  to  abstract,  which  de- 
notes the  quality  without  its  subject. 
The  names  of  Classes  are  abstract,  those 
of  individuals  concrete;  and  from  con- 
crete adjectives  are  made  abstract  sub- 
stantives.    See  Abstract. 

CONCRETIONARY  DEPOSITS.  In 
Geology,  a  designation  of  those  Recent  or 


CON 


CON 


Alluvial  strata,  which  include  calcareous 
and  other  deposits  from  springs,  stalac- 
tites, travertines,  bog  iron  -ore,  and  salt. 

CONCURRENTS.  Common  years  con- 
sist of  52  weeks  and  1  day,  and  Bissex- 
tile years  consist  of  52  weeks  and  2  days. 
The  day  or  two  days  supernumerary  are 
called  Concurrents,  because  they  concur 
with  the  Solar  Cycle,  whose  course  they 
follow.  The  first  year  of  this  cycle  is 
termed  Concurrent  1,  the  second  2,  the 
third  3,  the  fourth  4,  the  fifth  6  (instead 
of  5,  because  that  year  is  bissextile),  the 
sixth  7,  the  seventh  1,  the  eighth  2,  the 
ninth  4  (instead  of  3,  because  that  year 
is  likewise  bissextile),  and  thus,  with  the 
other  years,  always  adding  one  in  com- 
mon years,  and  2  in  bissextile  years  ;  and 
always  recommencing  with  1  after  having 
reckoned  7,  because  there  are  no  more 
than  7  Concurrents,  —  that  being  the 
number  of  days  in  a  week  and  of  the 
Dominical  Letters. 

CONDENSATION  (condenso,  to  thick- 
en). The  act  of  diminishing  the  bulk  of 
a  body,  by  compression,  as  in  the  conver- 
sion of  gases  into  liquids,  of  liquids  into 
solids ;  or  by  cold,  as  in  the  conversion 
of  steam  into  water. 

CONDE'NSER  (condenso,  to  thicken). 
1.  A  vessel  in  which  steam  is  condensed, 
or  converted  into  water,  by  the  applica- 
tion of  cold.  2.  An  apparatus  used  for 
detecting  the  presence  of  electricity,  by 
collecting  and  condensing  it  before  it 
gains  a  sufficient  degree  of  tension  to 
affect  the  electroscope.  Its  action  de- 
pends on  the  induction  of  electricity,  and 
on  this  being  held  in  a  latent  state. 

CONDENSING  SYRINGE.  A  hollow 
metallic  cylinder,  furnished  with  a  pis- 
ton, piston-rod,  and  receiver,  for  increas- 
ing the  density  of  air  in  a  given  space. 

CONDITIONAL  PROPOSITION.  In 
Logic,  a  proposition  which  asserts  the 
dependence  of  one  categorical  proposition 
on  another.  A  conditional  syllogism  is 
one  in  which  the  reasoning  depends  on 
such  a  proposition. 

CONDUCTION  (conduco,  to  bring 
with).  A  term  expressive  of  that  pro- 
perty by  which  certain  bodies  transmit 
heat,  or  electricity,  through  their  sub- 
stance. The  rate  at  which  this  equaliza- 
tion^ effected  in  any  body  is  the  measure 
of  its  conducting  power ;  and  substances 
are,  accordingly,  divided  into  good  and 
bad  conductors  with  reference  to  this 
power. 

CONDUCTORS  METALLIC.  A  term 
applied   to    long  metallic   rods,    whose 


points  are  raised  above  buildings  for  the 
purpose  of  attracting  or  receiving  the 
electric  fluid,  and  of  conducting  it  into 
the  earth,  or  into  water,  thereby  to  pre- 
vent such  buildings  from  being  struck 
by  lightning. 

CONDU'RRITE.  An  ore  of  copper 
found  in  a  vein  in  Condurrow  mine,  in 
Cornwall. 

CONDYLO'PODA  (/c6i/3t/\or,  a  joint, 
irovs,  irodbs,  a  foot).  Articulated  animals 
with  jointed  legs,  as  insects,  crabs,  and 
spiders. 

CONE  (kwvos,  a  cone).  A  geometri- 
cal solid,  with  a  circular  base,  tapering 
equally  upwards  until  it  terminates  in  a 
vertex  or  point.  A  right  line  drawn  from 
the  vertex  to  the  centre  of  the  base,  is 
termed  the  axis  of  the  cone.  When  this 
axis  is  at  right  angles  to  the  base, 
the  solid  is  termed  a  right  cone;  if 
otherwise,  it  is  an  oblique,  or  scalene 
cone. 

CONE,  in  BOTANY.  The  fruit  of 
the  Coniferae,  or  Fir-tribe  of  plants,  con- 
sisting of  a  conical  amentum,  of  which 
the  carpels  are  scale-like,  spread  open, 
and  bear  naked  seeds. 

CONE  OF  RAYS  The  rays  of  light 
which  fall  from  a  luminous  point  upon  a 
given  surface,  as  upon  the  object-glass 
of  a  telescope. 

,  CONE'NCHYMA  (kSi/o?,  a  cone,  ?-yXw- 
fia,  infusion).  A  term  applied  by  Mor- 
ren  to  that  form  of  parenchyma  in  plants, 
which  is  conical,  as  in  hairs. 

CONFERVA.  A  section  of  Algace- 
ous  plants,  consisting  of  simple  tubular 
jointed  species  inhabiting  fresh  water. 

CONFLA'TION  (conflo,  to  blow  to' 
gether).  The  process  of  casting  or  melt- 
ing of  metals. 

CO'NFLUENT  (confluo,  to  flow  toge- 
ther). Growing  together ;  a  term  syno- 
nymous with  connate,  expressive  of  the 
cohesion  of  homogeneous  parts. 

CONFO'RMABLE.  A  term  applied 
in  Geology  to  the  planes  of  one  set  of 
strata  which  are  parallel  to  those  of  an- 
other set  which  are  in  contact  with  them. 

CONGELATION  (congelo,  to  freeze). 
The  passing  from  a  fluid  to  a  partially  or 
wholly  solid  state,  by  the  agency  of  cold. 

CO'NGENER.  That  which  is  of  the 
same  kind;  a  term  applied  to  species 
which  belong  to  the  same  genus. 

CONGLOMERATE  (conglomero,  to 
heap  together).  Puddingslone.  Rounded 
water- worn  fragments  of  rock  or  pebbles, 
cemented  together  by  another  mineral 
substance,  which  may  be  of  a  silicious, 


CON 


CON 


calcareous,  or  argillaceous  nature.  The 
term  is  synonymous  with  the  Italian 
word  breccia. 

CONIC  SECTIONS.  The  designation 
of  that  science  which  treats  of  the  pro- 
perties of  certain  curves  which  are  formed 
by  the  cutting  of  a  cone.  These  curves, 
or  sections,  are  the  ellipsis,  the  parabola, 
and  the  hyperbola. 

CONICAL  PROJECTION.  A  me- 
thod of  describing  a  representation  of  a 
part  of  a  sphere  upon  a  plane. 

CO'NICINE.  A  vegeto-alkali  exist- 
ing in  all  parts  of  the  conium  maculatum, 
or  hemlock.  It  is  also  called  conia  and 
coneine. 

CONI'FERjE.  The  Fir  or  cone-bearing 
tribe  of  Dicotyledonous  plants.  Trees  or 
shrubs  with  a  stem  abounding  with  re- 
sin ;  leaves  linear,  acerose,  or  lanceolate ; 
flowers  monoecious,  or  dioecious ;  ovarium 
in  the  cones,  spread  open,  appearing  like 
a  flat  scale  destitute  of  style  or  stigma ; 
fruit  a  solitary  naked  seed  or  a  cone; 
seeds  with  a  hard  crustaceous  integu- 
ment. 

CONI'NjE.  The  Cone-shells ;  a  sub- 
family of  the  Strombidce,  or  Wing-shells, 
named  from  the  typical  genus  conus, 
having  the  spire  so  depressed  as  to  be 
turbinated,  and  scarcely  raised  above  the 
body-whorl;  the  aperture  is  always 
smooth  ;  the  outer  lip  without  any  lobe, 
and  only  slightly  detached  above. 

CONIRO'STRES  {conus,  a  cone,  ros- 
trum, a  beak).  A  large  group  of  the 
Insessores,  or  Perching  birds,  character- 
ized by  a  stout  beak,  more  or  less  conical, 
and  with  regular  edges,  including  the 
crows,  starlings,  finches,  hornbills,  and 
crossbills.  The  structure  of  their  feet 
enables  them  to  walk  on  the  ground  with 
nearly  the  same  facility  as  they  perch 
upon  trees. 

CO'NITE.  A  mineral  found  in  the 
Meissner  trap-hill  in  Hessia,  &c.  The 
same  name  has  been  applied  to  another 
pulverulent  mineral,  found  in  the  trap- 
hills  of  Kilpatrick  and  other  places. 

CO'NJUGATE  (conjugatus,  yoked  toge- 
ther). A  term  applied,  in  Mathematics, 
to  two  lines,  points,  &c,  when  considered 
together  in  any  property  in  such  a  man- 
ner that  they  may  be  interchanged  with- 
out altering  the  way  of  enunciating  the 
property.      ' 

CONJUGATION  (conjugo,  to  yoke 
together).  A  term,  in  grammar,  denot- 
ing all  the  inflexions  of  a  verb,  with  re- 
lation to  mood,  time,  number,  person, 
voice,  &c. 
89 


CONJUNCTION  (conjungo,  to  join 
together).  A  part  of  speech  used  to  join 
words  and  propositions  together.  It  is 
termed  copulative,  when  it  not  only  joins 
the  words,  but  indicates  that  the  things 
are  to  be  united  ;  disjunctive,  when  it 
unites  the  words,  but  indicates  that  the 
things  are  to  be  separated. 

CONJUNCTION  and  OPPOSITION. 
When  a  planet,  as  seen  from  the  earth, 
is  in  the  same  direction  as  the  sun,  it  is 
said  to  be  in  conjunction  with  the  sun. 
This,  however,  in  the  case  of  an  inferior 
planet,  may  be  either  when  it  passes  be- 
tween the  sun  and  the  earth,  or  when  it 
is  on  the  further  side  of  the  sun  ;  the  for- 
mer is  the  Inferior,  and  the  latter  the 
Superior  Conjunction.  A  superior  planet, 
never  passing  between  the  sun  and  the 
earth,  is  only  once  in  conjunction  with 
the  sun  during  its  revolution.  In  the 
point  of  its  orbit,  when  the  earth  is  be- 
tween it  and  the  sun,  the  planet  is  said 
to  be  in  Opposition  to  the  sun.  The  Con- 
junctions and  Oppositions  of  the  moon 
have  the  general  name  of  Syzygies. 

CONNATE  (connascor,  to  be  born  to- 
gether). Born  with  another ;  congenital. 
A  term  applied  in  botany  to  two  opposite 
leaves  united  at  their  bases,  as  in  the 
garden  honeysuckle. 

CONNE'CTIVE.  That  part  of  the 
stamen  in  plants  which  connects  the  two 
lobes  or  cells  of  the  anther ;  it  is  usually 
continuous  with  the  filament,  but  is  fre- 
quently enlarged  in  various  ways. 

CO'NOID  {ku>vos,  a  cone,  eldov,  like- 
ness). A  geometrical  solid,  formed  by 
the  motion  of  a  parabola  or  of  a  hyper- 
bola round  its  axis.  Conoids  vary  in 
thickness  in  comparison  with  their 
height,  according  to  the  proportions  of 
the  parabola,  or  hyperbola,  by  which  they 
are  generated.  The  spheroids,  some- 
times included  in  the  class  of  conoids, 
are  more  usually  limited  to  the  parabo- 
loid and  the  hyperboloid.  The  term 
conoid  is  sometimes  used  synonymously 
with  spheroid,  although  the  latter  has  no 
resemblance  to  single  cones,  and  but 
little  to  double  ones. 

CO'NSEQUENT.  In  Logic,  that  part 
of  a  conditional  proposition  which  de- 
pends on  the  other.  By  consequence  is 
meant  the  connexion  between  the  ante- 
cedent and  the  consequent  of  a  con- 
ditional proposition. 

CO'NSONANCE  {consono,  to  sound 
together).  A  term  applied,  in  Music,  to 
a  combination  of  harmonious  sounds.  See 
Chord. 


CON 


COP 


CONSTELLATION  (cum,  with,  stelLi, 
a  star).  A  group  of  stars,  designated 
by  the  name  of  some  man  or  lower  ani- 
mal. The  several  stars  of  a  constella- 
tion are  distinguished,  in  the  order  of 
their  brilliancy  or  apparent  magnitude, 
by  the  letters  of  the  English  and  Greek 
alphabets,  by  the  ordinal  numbers,  &c. 
Forty-eight  of  the  constellations  are  of 
unknown  antiquity;  the  twelve  which 
occupy  the  zodiac  are  termed  the  twelve 
signs. 

CO'NTINENT  (contineo,  to  hold  toge- 
ther). A  space  of  land  of  vast  extent, 
surrounded  by  water.  The  Old  Continent 
includes  the  three  divisions  of  Europe, 
Asia,  and  Africa,  and  is  so  named  from 
its  having,  till  the  discoveries  of  Colum- 
bus, in  1492,  been  the  only  one  known  to 
Europeans.  The  New  Continent  includes 
North  and  South  America. 

CONTINGENT.  A  term  applied  in 
Logic  to  the  matter  of  a  proposition  when 
the  terms  of  it  in  part  agree,  and  in  part 
disagree. 

CONTRACTILITY  (contraho,  to  draw 
together).  The  property  by  which  a  body 
contracts ;  by  which  a  fibrous  tissue  re- 
turns to  its  former  dimensions  after  being 
extended ;  by  which  the  muscular  fibre 
shortens  itself  on  the  application  of  a 
stimulus.  The  last  exhibition  of  this 
property  is  usually  called  irritability. 

CONTRADICTORY  PROPOSI- 

TIONS. Propositions  which,  having 
the  same  terms,  differ  both  in  quantity 
and  quality.  Contrary  propositions  are 
two  universals,  affirmative  and  negative, 
with  the  same  terms. 

CONTRARY  TERMS.  In  Logic, 
those  terms  which,  coming  under  some 
one  class,  are  the  most  different  of  all 
that  belong  to  that  class;  as  "wise"  and 
"foolish" 

CONVE'CTION  {conveho,  to  carry).  A 
mode  of  communication  of  heat  through 
fluid  bodies.  A  portion  of  water  or  of 
air  being  heated  above,  or  cooled  below, 
the  surrounding  portions,  expands  or 
contracts  in  magnitude,  and  thus  be- 
coming specifically  lighter  or  heavier, 
rises  or  sinks  accordingly,  carrying  with 
it  the  newly  acquired  temperature,  what- 
ever that  temperature  may  be. 

CONVERGENT;  DIVERGENT.  In 
Algebra,  an  indefinite  series  of  terms 
which  continually  diminish,  so  that  no 
number  of  them,  added  together,  will 
equal  a  given  number,  is  said  to  be  con- 
vergent, as  1  +  |  +  £  +  £  +  &e.  But, 
when  such  a  number  of  them  can  be 
90 


added  together  as  will  surpass  any  given 
number,  the  series  is  called  divergent,  as 
1  +  i  +  h  +  i  +  &c. 

CONVERSION.  In  Logic,  a  propo- 
sition is  said  to  be  converted,  when  its 
terms  are  transposed;  i.e.  when  the  sub- 
ject is  made  the  predicate,  and  the  pre- 
dicate the  subject :  when  nothing  more 
is  done,  this  is  called  simple  conversion. 
No  conversion  is  employed  for  any  logical 
purpose,  unless  it  be  illative ;  i.  e.  when 
the  truth  of  the  converse  is  implied  by 
the  truth  of  the  proposition  given  ;  e.  g., 
"  No  virtuous  man  is  a  rebel,  therefore 
no  rebel  is  a  virtuous  man." 

In  Geometry,  the  term  conversion  de- 
notes a  mode  of  changing  the  order  or 
magnitude  of  proportionals,  so  that  they 
continue  still  to  be  proportionals.  Thus, 
of  four  proportionals,  the  first  is  to  its 
excess  above  the  second,  as  the  third  to 
its  excess  above  the  fourth. 

CONVOLVULA'CE^S.  The  Bindweed 
tribe  of  Dicotyledonous  plants.  Herba- 
ceous plants  with  leaves  alternate ;  flowers 
regular,  monopetalous ;  stamens  inserted 
into  the  base  of  the  corolla ;  ovarium 
superior  2-4  celled  ;  seeds  albuminous. 

CO-O'RDINATES  (con,  together,  or- 
dino,  to  arrange).  A  term  applied  in 
Geometry  to  a  system  of  lines,  to  which 
points  under  consideration  are  referred, 
and  by  means  of  which  their  position  is 
determined.  In  plane  geometry  one  of 
these  lines  is  called  the  abscissa,  the 
other  the  ordinate. 

COPAHU'VIC  ACID.  A  name  ap- 
plied to  the  resin  of  copaiva,  said  to 
possess  the  same  composition  as  colo- 
phony. 

CO'PAL.  This  substance,  erroneously 
called  gum  copal,  is  the  concrete  juice  of 
the  Hymenaea  Courbaril ;  it  is  used  as  a 
varnish,  and  known  by  the  names  of 
jatahy  and  jatchy.  The  copal  of  the 
Mexicans  is  supposed  to  be  procured 
from  a  species  of  Icica. 

COPE'PODA.  An  order  of  the  ento- 
mostracous  Crustacea,  which  have  the 
body  divided  into  distinct  rings,  but 
without  carapace,  and  the  appendages  to 
the  mouth  in  considerable  numbers. 
The  animals  of  this  order  are  commonly 
termed  monoculous,  from  the  two  eyes 
being  united  in  one  mass. 

COPE'RNICAN  SYSTEM.  A  system 
of  Astronomy,  so  named  from  Nicholas 
Copernicus,  who  was  born  a.d.  1473,  at 
Thorn  in  Prussia.  He  taught,  as  Py- 
thagoras had  taught  before  him,  that  the 
sun  occupied  the  centre  of  the  universe, 


COR 


COR 


and  that  the  planets  moved  round  him  in 
elliptical  orbits  proportioned  to  their  size. 
This  system  was  established  by  the  new 
arguments  and  discoveries  of  Galileo, 
Kepler,  and  Newton.  The  great  prin- 
ciple on  which  it  rests  is  gravity,  or  that 
force  in  nature  by  which  all  the  planets 
are  attracted  to  the  centre  of  their  re- 
spective orbits. 

COPPER  {Cuprum,  quasi  ces  Cyprium ; 
from  the  island  Cyprus,  where  it  was 
first  wrought).  A  red  metal  found  in 
the  common  ore  called  copper  pyrites. 
Among  its  compounds  are  red  copper,  or 
the  protoxide ;  black  copper,  or  the  per- 
oxide; copper  glance,  or  the  protosul- 
phuret ;  resin  of  copper,  the  protochloride 
or  white  muriate ;  and  the  white  copper 
of  the  Chinese,  an  alloy  of  copper,  zinc, 
nickel,  and  iron. 

CO'PPERAS.  Sulphate  of  iron,  or 
green  vitriol.    See  Vitriol. 

COPPERNICKEL.  A  native  arseni- 
uret  of  nickel,  a  copper-coloured  mineral 
of  Westphalia, 

CO'PROLITE  (/coTrpor,  dung,  \i9os,  a 
stone).  The  petrified  faecal  matter  of 
carnivorous  reptiles,  resembling  an  ob- 
long pebble  or  a  kidney  potato,  and  found 
at  Lyme  Regis  in  Dorsetshire. 

CO'PULA.  In  Logic,  that  part  of  a 
proposition  which  affirms  or  denies  the 
predicate  of  the  subject;  viz.,  is,  or  is 
not,  expressed  or  implied. 

COR  CA'ROLI.  A  modern  northern 
constellation,  consisting  of  three  stars. 

COR  HYDR^E.  A  star  of  the  first 
magnitude  in  the  southern  constellation 
Hydra. 

COR  LEO'NIS.  Another  name  for 
Regulus,  a  star  of  the  first  magnitude  in 
the  constellation  Leo. 

COR  SCORPIO'NIS.  Another  name 
for  Antares,  a  star  of  the  first  magnitude 
in  the  zodiacal  constellation  Scorpio. 

CORACI'IISLE  {coracias,  the  roller). 
Coraciine  Birds,  or  Rollers ;  a  family  of 
the  Excurtrices  of  Macgillivray,  the  In- 
sessores  of  other  writers,  indigenous  in 
warm  climates,  and  for  the  most  part 
gaudily  coloured. 

CORAL  RAG.  A  subdivision  of  the 
middle  Oolitic  formation,  named  from 
its  containing  abundant  remains  of  corals 
of  various  kinds. 

CORAL  RED.  The  calcareous  in- 
ternal skeleton  of  a  polypipherous  ani- 
mal, consisting  of  carbonate  of  lime, 
coloured  with  oxide  of  iron,  and  ani- 
mal matter. 

CORALLI'DiE  {corallum,  coral).  Co- 
91 


rallicolce.  A  family  of  compound  polyps, 
yielding  the  substance  called  coral,  and 
constituting  the  third  order  of  the  class 
Polypi. 

CO'RALLINE  DEPOSITS.  In  Geo- 
logy, a  designation  of  those  recent  or 
alluvial  strata,  which  consist  of  the 
marine  banks,  shoals,  and  islands,  en- 
tirely composed  of  corals. 

CO'RCULUM  (dim.  of  cor,  the  heart). 
The  embryo,  or  vital  principle  of  a  seed, 
so  named  from  its  frequent  resemblance, 
in  form,  to  a  little  heart.  It  consists  of 
two  parts,  the  rostellum,  or  radicle,  which 
elongates  downward  to  form  a  root ;  and 
the  plumula,  or  feather,  which  lengthens 
upward  to  form  a  stem  and  leaves. 

CO'RDATE  (cordatus,  from  cor,  a 
heart).  Heart-shaped  ;  having  two 
rounded  lobes  at  the  base,  as  applied  to 
certain  leaves. 

CORIA'CEOUS  (corium,  hide).  That 
which  has  the  texture  of  rough  skin,  as 
the  leaves  of  prunus  laurocerasus. 

CO'RMUS.  The  dilated  base  of  the 
stem  of  monocotyledonous  plants,  inter- 
vening between  the  roots  and  the  first 
buds,  and  forming  the  reproductive  por- 
tion of  the  stem  in  acaulescent  plants. 
It  occurs  in  colchicum,  in  crocus,  &c. 

CO'RNEOUS  {cornu,  a  horn).  Horny; 
resembling  the  colour  or  substance  of 
horn,  as  the  epidermis  of  some,  and  the 
operculum  of  other,  spiral  shells ;  the 
albumen  of  many  plants,  &c. 

CO'RNEULE.  A  diminitive  of  cornea ; 
a  term  applied  to  the  minute  transpa- 
rent segments  which  defend  the  com- 
pound eyes  of  insects. 

CORNI'CULATE  {corniculum,  a  little 
horn).  Horned ;  terminating  in  a  horn- 
like process,  as  the  fruit  of  trapa  bi- 
cornis. 

CORNU  AMMO'NIS.  An  old  Latin 
name  for  the  fossil  shell,  commonly  called 
ammonite,  from  its  fancied  resemblance 
to  the  horn  with  which  the  head  of  Ju- 
piter Ammon  was  sculptured.  See  Am- 
monite. 

CORNU'BIANITE.  A  slaty  rock 
abundant  in  the  western  part  of  Corn- 
wall, in  contact  with  granite.  It  is  of  a 
dark  blue  or  purple  colour,  uniform, 
striped  or  patched,  hard  and  laminated. 

CORO'LLA  (dim.  of  corona,  a  crown). 
Literally,  a  little  crown.  The  internal 
envelope  of  the  floral  apparatus.  Its 
separate  pieces  are  called  petals;  when 
these  are  distinct  from  each  other,  the 
corolla  is  termed  poly-petalous ;  when 
they  cohere,  gamo-petalous,  or  incorrectly 


COR 


COT 


mono-petalous.  A  petal,  like  a  sepal, 
may  be  spurred,  as  in  violet.  Compare 
Calyx. 

CO'ROLLARY.  A  corollary  to  a  geo- 
metrical proposition  is  a  statement  of 
some  truth,  which  is  an  obvious  conse- 
quence of  the  proposition.  The  term  is 
derived  from  the  Latin  corollarium,  a 
reward  given  to  actors,  champions,  or 
fencers,'  above  their  due. 

CORO'NA  AUSTRA'LIS  et  BOREA'- 
LIS.  The  Southern  Crown  and  the 
Northern  Crown  ;  two  of  the  old  constel- 
lations of  Ptolemy,  the  former  in  the 
southern,  the  latter  in  the  northern 
hemisphere. 

CO'RONATED  {corona,  a  crown). 
Crowned ;  a  term  applied  to  spiral  shells 
which  have  their  whorls  more  or  less 
surmounted  by  a  row  of  spines  or  tuber- 
cles, as  in  the  typical  volutes,  several 
cones,  mitres,  &c. 

CORPU'SCULAR  THEORY  {corpus- 
culum,  a  little  body).  A  theory  for  ex- 
plaining the  nature  of  light.  According 
to  this,  the  sun  and  all  other  luminous 
bodies  have  the  property  of  emitting  cor- 
puscles, or  exceedingly  minute  particles 
of  their  substance,  with  prodigious  velo- 
city. Hence  it  has  been  also  termed  the 
Theory  of  Emission.  See  Undulatory 
Theory. 

CORRO'SIVE  SUBLIMATE.  The 
bichloride,  formerly  called  the  oxymu- 
riate,  of  mercury. 

CO'RRUGATE  {cum,  with,  ruga,  a 
wrinkle).  Wrinkled;  folded  up  in  every 
direction,  as  in  the  aestivation  of  the 
poppy. 

CORTI'NA.  A  curtain ;  a  name  given 
to  a  portion  of  the  velum  of  fungaceous 
plants,  which  adheres  to  the  margin  of 
the  pileus  in  fragments. 

CORU'NDUM.  A  stone  found  in 
India  and  China;  it  crystallizes  in  six- 
sided  prisms,  which,  from  their  hardness, 
are  termed  adamantine  spar.  The  ame- 
thyst, ruby,  sapphire,  and  topaz,  are 
considered  as  varieties  of  this  spar,  dif- 
fering from  one  another  chiefly  in  colour. 
These  are  termed  Oriental  gems ;  but  the 
names  are  applied  to  stones  of  other 
countries.  Jameson  distinguishes  three 
species  of  corundum,  the  octohedral,  the 
rhomboidal,  and  the  prismatic  or  chryso- 
beryl. 

CORVI'DiE  {corvus,  a  crow).  Corvine 
birds,  or  Crows ;  a  family  of  the  Insessores, 
or  of  the  Excur trices  of  Macgillivray, 
including  the  crow,  the  raven,  the  mag- 
pie, the  jay,  and  other  conirostral  birds. 
92 


CORVUS.  The  Crow;  a  southern 
constellation,  consisting  of  nine  stars, 
the  principal  of  which  is  Algorab.  It  is 
sometimes  called  Hydra  et  Corvus,  the 
Corvus  resting  on  part  of  the  body  of 
Hydra. 

CO  RY'D  ALINE.  A  vegeto-alkali, 
found  in  the  root  of  Corydalis  bulbosa 
and  fabacea. 

CORYLA'CEiE.  The  Nut  tribe  of 
Dicotyledonous  plants,  named  from  the 
genus  corylus,  and  comprising  the  oak, 
the  beech,  the  hazel,  the  hornbeam,  and 
the  sweet  chestnut.     See  Cupulifercc. 

CO'RYMB.  A  form  of  inflorescence, 
in  which  the  lower  stalks  are  so  long 
that  their  flowers  are  elevated  to  the 
same  level  as  that  of  the  uppermost 
flowers.  The  expansion  of  the  flowers  of 
a  corymb  is  centripetal.     See  Fascicle. 

CO'RYMBOSE.  That  arrangement  of 
the  ramifications  of  plants,  in  which  the 
lower  branches  or  pedicles  are  so  long  as 
to  bring  the  leaves  or  flowers  to  the  same 
level  as  that  of  the  upper  ones. 

CO-SECANTS,  CO-SINES,  CO-TAN- 
GENTS. These  are  the  secants,  sines, 
and  tangents,  of  arcs  which  are  the  com- 
plements of  those  in  question.  See  Trigo- 
nometry. 

CO'SMICAL  (koo-juop,  the  universe). 
A  term  opposed  to  acronychal,  and,  as 
such,  denotes  the  rising  or  setting  of  a 
star  in  the  morning  at  the  moment  of 
sunrise.  The  cosmical  and  acronychal 
risings  of  a  star  are  invisible  to  the  naked 
eye,  because  the  light  of  the  sun  in  the 
horizon  effaces  that  of  the  star.  See 
Heliacal. 

COSMO'GRAPHY  {kov/jlo?,  the  uni- 
verse, ypd<p(d,  to  describe).  A  description 
of  the  system  of  the  universe;  a  term 
differing  from  Geography,  as  a  whole  dif- 
fers from  its  part.  The  term  should  be 
distinguished  from  cosmogony  {yovrj,  ge- 
neration), which  relates  to  the  origin  and 
creation  of  the  world ;  and  from  cosmo- 
logy (\070p,  account),  which  treats  of  the 
metaphysical  philosophy  of  the  constitu- 
tion of  the  world. 

CO'TTON  {kutun,  Arab.).  The  hairy 
covering  of  the  seeds  of  several  species 
of  Gossypium.  The  cotton-plant  must 
not  be  confounded  with  the  cotton-tree 
{Bombax),  the  cotton  of  which  cannot  be  ' 
manufactured. 

COTYLE'DON  (koti/\m<5wi/,  a  cavity). 
The  seed-lobe  of  a  plant.  Plants  have 
been  distinguished,  with  reference  to  the 
number  of  their  cotyledons,  into  di- 
cotyledonous, or  those  which  have  two 


CRA 


CRI 


cotyledons  in  their  seeds;  mono-cotyle- 
donous,  or  those  which  have  only  one; 
and  a-cotyledonous,  or  those  which  have 
none. 

COUCH.  The  heap  of  moist  barley, 
about  16  inches  deep,  on  the  malt-floor. 

COU'MARIN.  A  neutral  substance, 
extracted  from  the  tonka  bean,  the  fruit 
of  the  Coumarouna  odorata,  and  the 
flowers  of  the  melitot. 

COU'NTERPOINT  (contra  punctum, 
point  against  point).  A  term  in  Music, 
synonymous  with  harmony,  and  derived 
from  the  old  method  of  placing  the  stem- 
less  points,  or  notes,  against  or  over  one 
another,  in  compositions  of  two  or  more 
parts. 

COURONNE  DE  TASSES.  Lite- 
rally, a  crown  or  circle  of  cups.  An  ap- 
paratus employed  in  voltaic  electricity, 
consisting  of  a  circle  of  cups  containing 
salt  water,  and  connected  together  by 
compound  metallic  arcs  of  copper  and 
zinc. 

COU'ZERANITE.  A  mineral  found 
in  limestone,  in  the  deep  defiles  of  Sa- 
leix  called  des  Couzerans. 

CRA'CIDJE  (crax,  a  curassow).  The 
Curassows ;  a  group  of  the  Rasores,  or 
Scratching  birds,  the  legs  of  which  are 
unarmed  with  spurs,  and  the  hind  toe 
so  much  developed,  as  to  give  them  con- 
siderable power  in  perching. 

CRAG.  A  provincial  term  in  Norfolk 
and  Suffolk  for  certain  tertiary  deposits 
usually  composed  of  sand  with  shells, 
belonging  to  the  older  pliocene  period. 

CRANIO'SCOPY  (upaviov,  the  skull, 
cKoireu),  to  investigate).  An  investiga- 
tion of  the  skull.  Dr.  Prichard  has  cha- 
racterized the  primitive  forms  of  the 
skull  according  to  the  width  of  the 
bregma,  or  space  between  the  parietal 
bones:  hence — 

1.  The  steno-bregmate  (o-rei/o?,  narrow), 
or  ^Ethiopian  variety. 

2.  The  meso-bregmate  (necros,  middle), 
or  Caucasian  variety. 

3.  The  platy-bregmate  (ttAcutup,  broad), 
or  Mongolian  variety. 

CRANK.  A  mechanical  contrivance 
for  converting  a  revolving  into  an  alter- 
nate motion. 

CRASS ULA'CE^.  The  House-leek 
tribe  of  Dicotyledonous  plants,  named 
from  the  gertus  crassula.  Succulent  herbs 
or  shrubs,  with  showy  flowers  usually  in 
cymes,  sepals  from  3  to  20,  petals  distinct 
or  cohering,  stamens  inserted  with  the 
petals,  fruit  of  several  follicles,  opening 
on  their  face. 
93 


CRA'TER  (crater,  a  large  cup  or  bowl). 
The  circular  cavity  at  the  summit  of  a 
volcano,  from  which  the  volcanic  matters 
are  ejected.  Besides  the  craters  of  erup- 
tion, more  extensive  craters  are  supposed 
to  have  been  formed  by  the  elevation  of 
the  ground  previous  to  volcanic  erup- 
tions, and  are  therefore  called  craters  of 
elevation. 

CRATER  (in  Astronomy).  The  Cup, 
a  southern  constellation  consisting  of 
thirty-one  stars. 

CREMOCA'RPIUM  (Kpe/xau,  to  sus- 
pend, Kap7r6r,  fruit).  In  Botany,  a  com- 
pound fruit,  2-5-celled,  inferior ;  cells 
1-seeded,  indehiscent,  dry,  perfectly  close 
at  all  times ;  when  ripe,  separating  and 
hanging  from  a  common  axis.  Mirbel 
restricts  the  term  to  the  fruit  of  Ura- 
belliferae.     See  Polakenium. 

CRENA'TED  (crena,  a  notch  or  slit). 
A  term  applied  to  shells,  which  present 
small  indentations,  generally  of  a  sharp 
and  regular  form,  frequently  observed  on 
the  outer  lip  of  spiral  shells,  particularly 
on  many  of  the  typical  mitres.  A  leaf  is 
said  to  be  crenelled,  when  its  margin  has 
rounded  toothings  or  teeth. 

CRE'OSOTE  (xpeas,  flesh,  cobfr,  to 
preserve).  Kreasote.  An  oily,  colour- 
less, transparent  liquid,  discovered  first 
in  pyroligneous  acid,  and  subsequently 
in  the  different  kinds  of  tar.  Its  name 
is  derived  from  its  preventing  the  putre- 
faction of  meat  or  fish,  when  dipped  in  it. 

CREPITATION  (crepito,  to  crackle). 
The  crackling  noise  occasioned  by  press- 
ing cellular  membrane  which  contains 
air ;  also  the  sound  emitted  by  certain 
salts  during  calcination. 

C  REP U'SCULARI A  (crepusculum,  the 
twilight).  The  twilight-moths,  or  Hawk- 
moths  ;  a  tribe  of  Lepidopterous  insects, 
corresponding  with  the  Linnaean  genus 
Sphinx,  and  named  from  their  general 
habit  of  flying  only  in  twilight. 

CRETA'CEOUS  SYSTEM  (creta, 
chalk).  A  geological  series  of  rocks,  in 
which  calcareous  matter  forms  the  pre- 
dominating mass,  to  which  the  flints  and 
other  extraneous  minerals  are  subordi- 
nate. Part  of  it  seems  to  have  been  de- 
posited in  a  sea  of  considerable  depth, 
and  all  of  it  is  marine.  In  a  general  sense, 
it  is  distinguished  into  the  Green  Sand 
and  the  Chalk  Formations. 

CRFCHTONITE.  A  mineral  found 
associated  with  anatase,  and  on  rock 
crystal,  in  Dauphiny. 

CRINOI'DEA  (uptvov,  a  lily,  eldos, 
like).     A   term   applied    to  a  tribe   of 


CRU 


CRY 


Echino-dermatous  animals  which  resem- 
ble lilies,  of  which  the  fossils  called  stone- 
lilies  and  encrinites  are  examples.  The 
fossil  remains  called  trochi  and  St.  Cuth- 
bert's  beads  are  separated  portions  of  the 
earthy  framework  of  encrinites. 

CRITICAL  PHILOSOPHY.  A  term 
sometimes  applied  to  the  metaphysical 
system  of  Kant  from  his  famous  work 
entitled  "Criticism  of  Pure  Reason." 

CROCO'NIC  ACID  (crocus,  saffron). 
An  acid  derived  from  carbonic  oxide,  and 
named  from  the  saffron  colour  of  its 
salts,  called  croconates. 

CROCUS  (/cpoKo?).  Saffron.  An  old 
term  applied  to  oxides  and  other  prepa- 
rations of  the  metals,  from  their  saffron 
colour:  thus  we  have  crocus  marlis,  or 
oxide  of  iron ;  crocus  metallorum,  or 
oxide  of  antimony ;  crocus  Veneris,  or 
oxide  of  copper. 

CROP,  or  CRAW.  A  sort  of  prelimi- 
nary stomach  in  some  birds,  formed  by 
an  expansion  of  the  oesophagus.  Com- 
pare Gizzard. 

CROP  OUT.  A  technical  term,  to 
denote  the  rising  up,  or  exposure  at  the 
surface,  of  a  stratum  or  series  of  strata. 

CROSS-STONE.  Harmotone,  or  py- 
ramidal zeolite,  found  in  mineral  veins 
and  agate  balls. 

CROTA'LIDjE  (crotalus,  a  rattle- 
snake). A  family  of  Ophidian  reptiles, 
including  the  Rattlesnakes  and  the 
Vipers,  and  all  the  venomous  species. 
They  are  distinguished  from  the  Colu- 
beridae  principally  by  the  character  of  the 
teeth. 

CROTCHET.  In  Music,  a  character 
constituting  the  fourth  part  of  a  semi- 
breve  ;  its  duration,  in  slow  time,  is 
about  one  second. 

CROTO'NIC  ACID.  Iatrophic  acid. 
A  solid,  volatile,  and  highly  poisonous 
acid  derived  from  croton  oil,  the  fat  oil 
of  the  seeds  of  Croton  tiglium. 

CRU'CIATE  (crux,  crucis,  a  cross).  A 
designation  of  the  corolla  of  cruciferous 
plants,  from  the  resemblance  of  the 
arrangement  of  the  petals  to  the  pieces 
of  a  Maltese  cross. 

CRU'CIBLE.  An  earthern  vessel  in 
which  substances  are  exposed  to  high 
temperatures.  The  term  is  derived  either 
from  crux,  a  cross,  which  the  alchemists 
stamped  upon  the  vessel ;  or  from  crucio, 
to  torture,  because  the  metals  were  tor- 
tured in  crucibles,  in  order  to  convert 
them  into  gold. 

CRUCI'FERiE  (crux,  crucis,  a  cross, 
fero,  to  bear).  The  Cruciferous  tribe  of 
94 


Dicotyledonous  plants.  Herbaceous  plants 
with  leaves  alternate ;  flowers  polype- 
talous  ;  sepals  4,  deciduous,  cruciate, 
alternating  with  4  cruciate  petals ;  sta- 
mens 6,  hypogynous,  tetradynamous ; 
fruit  a  siliqua  or  a  silicula. 

CRUST  OF  THE  EARTH.  The  super- 
ficial parts  of  our  planet  which  are  acces- 
sible to  observation. 

CRUSTA.  A  term  applied  to  the  brittle 
crustaceous  thallus  of  lichens;  to  the 
bony  covering  of  the  crab,  the  lobster,  &c. 

CRUSTA'CEA  (crusta,  a  shell).  A 
class  of  articulated  animals  with  an  ex- 
terior shell  which  is  generally  hard  and 
calcareous,  and  is  cast  off  periodically,  as 
in  the  crab,  the  shrimp,  the  lobster,  &c. 

CRUX.  The  Cross;  a  southern  con- 
stellation, situated  close  to  the  hinder 
legs  and  under  the  body  of  Centaurus. 

CRY'OLITE  (kPvos,  frost,  \i6os,  a 
stone).  A  mineral  consisting  of  the 
double  hydrorluate  of  alumina  and  soda, 
occurring  in  gneiss.  The  term  is  derived 
from  the  property  which  this  mineral 
presents  of  fusing  readily  in  the  flame  of 
a  candle. 

CRYO'PHORUS  (>cpuop,  cold,  0epa>,  to 
bring).  An  instrument  for  exhibiting  the 
degree  of  cold  produced  by  evaporation. 
The  term  denotes  frost-bearer,  and  it  is 
well  illustrated  by  the  Cryophorus  of 
Wollaston,  which  consists  of  two  hollow 
glass  balls  connected  by  a  bent  glass 
tube,  one  of  them  containing  water ;  the 
cold  is  transferred  from  one  ball  to  the 
other. 

CRY'PTA  (Kpvmos,  concealed).  Glan- 
dules impresses.  A  term  applied  to  the 
vesicular  receptacles  of  oil  found  in  the 
leaves  of  the  orange  and  of  all  myrta- 
ceous  plants. 

CRYPTOBRANCHIA'TA  (kpi/ttto?, 
concealed,  /?p«7x<n,  gills).  A  designa- 
tion of  those  molluscous  and  articulate 
animals,  which  have  no  conspicuous 
gills. 

CRYPTOGA'MIA  (kPvht6<:,  concealed, 
ydfxos,  nuptials).  A  class  of  plants,  in- 
cluding ferns,  mosses,  sea-weeds,  &c.,  in 
which  the  fructification,  or  organs  of  re- 
production, are  concealed.  These  are 
also  called  agamous,  acotyledonous,  and 
cellular  plants.     See  Phanerogamia. 

CRYPTO'GRAPHY  (Kpvmos,  secret, 
7pci0oj,  to  write).  The  art  of  writing  in 
a  secret  manner,  as  in  cypher.  See 
Cypher. 

CRYPTONEU'RA  (kputttop,  concealed, 
vevpov,  a  nerve).  A  term  applied  by  Ru- 
dolph! to  those  radiate  animals  in  which 


CRY 


CUB 


no  nervous  filaments  or  masses  have  been 
discovered.  They  correspond  with  the 
Acrita  of  Macleay,  and  the  Protozoa  and 
Oozoa  of  other  writers. 

CRY'STAL  (Kpi'/<rTa\\o5,  ice).  A  solid 
body  of  a  limited  symmetrical  form,  in- 
cluded by  plane  surfaces.  In  organized 
bodies  spherical  forms  predominate,  whilst 
unorganized  bodies  are  mostly  angular. 
Quartz,  being  often  found  in  a  crystalline 
form,  and  being  transparent  like  ice,  was 
called  rock-crystal ;  and  hence  all  other 
minerals  of  regular  forms  are  called 
crystals,  whether  they  be  clear  or  opaque. 

1.  The  structure  of  a  crystal  is  the 
arrangement  of  its  component  parts,  and 
this  is  ascertained  by  splitting  it  in  the 
direction  of  its  planes  of  cleavage ;  the 
crystal  is  thus  obtained  in  its  primitive 
form,  and,  when  this  differs  from  the 
figure  at  first  presented  by  the  body,  the 
latter  is  called  the  secondary  form. 

2.  Primitive  Forms.  By  the  term 
"primitive  form,"  Haiiy  designates  the 
nucleus  of  crystals  ;  "  secondary  forms" 
are  varieties  which  differ  from  the  primi- 
tive form.  The  primitive  forms  of  crys- 
tals are  the  tetrahedron,  the  parallelopi- 
pedon,  the  octohedron,  the  hexagonal 
prism,  the  rhombic  dodecahedron,  and 
the  dodecahedron  with  triangular  faces. 
To  the  parallelopipedon  belong  the  cube 
and  the  rhombohedron. 

3.  The  angles  at  which  the  edges  of 
the  planes  or  faces  of  a  crystal  meet,  are 
called  plane  angles ;  and  the  point  formed 
by  the  union  of  three  or  more  of  these,  a 
solid  angle.  The  lines  which  join  these 
points,  and  pass  through  the  middle  of 
the  crystal,  are  called  its  axes ;  there  are 
usually  three  of  these,  a  principal  axis, 
and  two  secondary  or  subordinate  axes. 

4.  In  the  Wernerian  language  of  crys- 
tallization, the  following  terms  are  em- 
ployed : — When  a  secondary  form  differs 
from  the  cube,  the  octohedron,  &c,  only 
in  having  several  of  its  angles  or  edges 
replaced  by  a  face,  this  change  of  the 
geometrical  form  is  called  a  truncation. 
The  alteration  in  the  principal  form  pro- 
duced by  two  new  faces  inclined  to  one 
another,  and  which  replace,  by  a  kind  of 
bevel,  an  angle  or  an  edge,  is  called  a 
bevelment.  When  these  new  faces  are  to 
the  number  of  three  or  more,  they  pro- 
duce what  Werner  termed  a  pointing  or 
acumination.  When  two  faces  unite  by 
an  edge  in  the  manner  of  a  roof,  they 
have  been  called  culmination.  The  term 
replacement  is  occasionally  used  for  bevel- 
ment. 

95 


CRYSTAL  ELECTRICITY.  A  term 
sometimes  applied  to  thermo-electric  polar 
tension,  from  its  being  displayed  princi- 
pally in  crystallized  substances,  especially 
in  those  which  belong  to  the  mineral 
kingdom.  The  crystals  which  exhibit 
this  property  are  termed  thermo-electric 
crystals,  as  tourmaline. 

CRYSTALLINE  LENS.  A  thick  com- 
pact humour,  in  form  of  a  flattish  convex 
lens,  situated  in  the  middle  of  the  eye, 
and  causing  that  refraction  of  the  rays  of 
light  which  is  necessary  to  make  them 
meet  in  the  retina,  and  form  an  image 
thereon,  whereby  vision  is  performed. 

CRYSTALLIZATION  (KpvaraWos,  a 
crystal).  The  process  by  which  the  par- 
ticles of  liquid  or  gaseous  bodies  form 
themselves  into  crystals,  or  solid  bodies 
of  a  regularly  limited  form. 

Crystallization,  Alternate.  This  term 
is  applied  to  a  phenomenon  which  takes 
place  when  several  crystallizable  sub- 
stances, having  little  attraction  for  each 
other,  are  present  in  the  same  solution. 
That  which  is  largest  in  quantity  and 
least  soluble  crystallizes  first,  in  part; 
the  least  soluble  substance  next  in  quan- 
tity then  begins  to  separate ;  and  thu3 
different  substances,  as  salts,  are  often 
deposited  in  successive  layers  from  the 
same  solution. 

CRYSTALLOGRAPHY  {KpixnaWos, 
a  crystal,  ypaQw,  to  describe).  The  science 
which  investigates  the  relation  of  crys- 
talline forms,  and  the  origin  and  struc- 
ture of  crystals. 

CTE'NOBRANCHIA'TA  (/cretc,  a 
comb,  /3pa7x«a>  gills).  A  term  synony- 
mous with  Pectinibranchiata,  applied  to 
an  order  of  Gasteropods  which  breathe 
by  means  of  pectinated  gills. 

CTENOI'DES  (KTeif,  a  comb,  eldos, 
likeness).  An  order  of  fishes,  furnished 
with  scales  composed  of  layers  with  pec- 
tinated or  toothed  posterior  margins. 

CU'BATURE.  The  measurement  of 
the  contents  of  a  solid  body,  or  the  find- 
ing a  cube  equal  to  it. 

CUBE  (nv/3ov,  a  cube).  A  geometrical 
solid,  contained  by  six  equal  squares.  It 
is  the  measuring  unit  of  solid  content,  as 
the  square  is  that  of  superficial  extent, 
or  area. 

CUBE  ORE.  Hexahedral  Olivenite, 
or  Wurfelerz ;  a  green  mineral,  which 
occurs  crystallized  in  a  perfect  cube, 
in  Cornish  mines,  accompanied  with 
iron-shot  quartz.  It  is  an  arseniate  of 
iron. 
CUBIC   EQUATION.     An    equation 


CUM 


CUR 


which  involves  the  cube,  or  third  power 
of  the  unknown  quantity.  Like  equations 
of  any  other  degree,  cubic  equations  are 
either  pure  or  adjected. 

CUCULI'D^E  [cuculus,  a  cuckoo).  The 
Cuckoo  tribe ;  a  family  of  the  Scansores, 
or  Climbing  birds,  characterized  by  the 
short  and  slender  structure  of  the  feet, 
and  by  their  migratory  habits.  Mac- 
gillivr'ay  places  them  next  to  the  goat- 
suckers, from  the  great  similarity  of  their 
digestive  organs.  They  are  little  capable 
of  walking,  and  belong  to  a  group,  of 
which  the  habit  is  to  perch  on  trees  or 
shrubs,  whence  they  glide  after  passing 
insects. 

CUCU'LINjE.  A  family  of  bees  which, 
having  no  femoral  plates  for  transporting 
pollen,  resort  to  the  combs  of  other  bees 
in  order  to  deposit  their  eggs— a  habit 
resembling  that  of  the  cuculus,  or  cuckoo. 
CUCU'LLATE  (cucullus,  a  hood). 
Hooded ;  having  the  apex  and  sides 
curved  inward,  as  the  upper  sepal  of 
aconite. 

CUCURBIT  A'CEjE  ( cucurbita,  a 
gourd).  The  Gourd  tribe  of  Dicotyle- 
donous plants.  Climbing  plants  with 
leaves  palmated,  succulent ;  flowers  uni- 
sexual, monopetalous ;  stamens  cohering 
in  three  parcels ;  ovarium  inferior ;  fruit 
fleshy ;  seeds  flat ;  testa  coriaceous. 

CUDBEAR.  A  neutral  colouring  mat- 
ter, prepared  from  the  Leconora  tartar ea 
and  other  lichens,  and  named  from  Sir 
Cuthbert  Gordon.  The  Germans  call  it 
persio. 

CULFCIDjE  (culex,  a  gnat).  The 
Gnat  tribe ;  a  family  of  Dipterous  in- 
sects, belonging  to  the  section  Nemocera, 
distinguished  by  their  beautifully  tufted 
antennae. 

CULM.  The  peculiar  stem  of  grasses, 
sedges,  &c.  Also,  a  provincial  synonym 
of  anthracite. 

CULMINATION  (culmen,  the  top  of 
any  thing).  The  transit  or  passage  of  a 
star  over  the  meridian,  or  the  point  of  its 
highest  altitude. 

CU'MBRIAN  GROUP.  A  group  of 
rocks  constituting  the  lower  series  of  the 
Clay-slate  system,  upwards  of  3000  feet 
in  thickness,  and  comprising  the  horn- 
blendic  clay-slate,  chiastolite-slate,  and 
clay-slate. 

CUMULO'STRATUS.  The  twain- 
cloud;  a  composite  modification  of  clouds, 
known  by  its  generally  flat  base,  with  a 
superstructure  resembling  a  bulky  cumu- 
lus overhanging  the  base  in  large  fleecy 
protuberances,  or  rising  into  the  forms 
96 


of  rocks  and  mountains.  The  Latin  term 
is  derived  from  the  frequent  grouping  of 
considerable  cumuli,  or  masses,  upon  a 
common  stratum,  or  base;  the  English 
term,  from  the  frequently  visible  coales- 
cence of  two  other  modifications,  viz.  the 
cirrus  and  the  cumulus.  This  cloud 
may  always  be  regarded  as  a  stage  to- 
wards the  production  of  rain  or  snow, 
and,  in  this  case,  it  always  ends  in  the 
nimbus. 

CU'MULUS  (Lat.  aheap).  The  stacken- 
cloud ;  a  primary  form  of  clouds,  known 
by  its  irregular  hemispherical  or  heaped 
superstructure,  and  usually  flattened 
base.  It  is  formed  by  the  gathering 
together  of  detached  clouds,  which  then 
appear  stacked  into  one  large  and  ele- 
vated mass.  It  may  be  called  the  cloud 
of  day,  as  it  usually  exists  only  during 
that  period. 

CUMY'L.  The  compound  radical  of  a 
series  of  compounds  procured  from  the 
seeds  of  the  Cuminum  Cyminum. 

CU'NEIFORM(cwwews,  a  wedge, /orma, 
likeness).  Cuneate.  Wedge-shaped ;  in- 
versely triangular,  with  rounded  angles ; 
a  shape  characteristic  of  certain  bivalves, 
analogous  to  the  clavate  form  among  uni- 
valves. 

Cuneiform  Letters.  A  term  applied 
to  the  inscriptions  found  on  old  Baby- 
lonian and  Persian  monuments,  from 
the  characters  being  formed  like  a 
wedge. 

CUPEL  (kuppel,  German).  A  small 
flat  cwp-like  crucible,  made  of  bone  ash, 
used  in  the  assays  of  the  precious  metals, 
which  are  fused  on  a  cupel  with  lead. 

CUPELLA'TION.  The  process  of  pu- 
rifying gold  and  silver  by  melting  them 
with  lead,  which  becomes  first  oxidated, 
then  vitrified,  and  sinks  into  the  cupel, 
carrying  along  with  it  all  the  baser 
metals,  and  leaving  the  gold  or  silver 
upon  its  surface. 

CU'PULA.  A  form  of  involucrum, 
occurring  in  the  oak,  the  beech,  the 
hazel ;  and  consisting  of  bracts  not  much 
developed  till  after  flowering,  when  they 
cohere  by  their  bases,  and  form  a  kind 
of  cup. 

CUPULI'FERjE  {cupula,  a  small  cup). 
The  Oak  tribe  of  Dicotyledonous  plants. 
Trees  or  shrubs  with  leaves  alternate ; 
flowers  amentaceous,  dioecious,  apetalous; 
ovarium  inferior,  inclosed  in  a  cupule  ; 
fruit  a  horny  or  coriaceous  nut. 

CURCUMA  PAPER.  Paper  stained 
with  a  decoction  of  turmeric,  and  em- 
ployed by  chemists  as  a  test  of  free  alkali, 


CUR 


CUR 


by  the  action  of  which  it  receives  a  brown 
stain. 

CU'RCUMINE.  The  colouring  matter 
of  turmeric,  obtained  in  a  state  of  purity 
by  separating  it  from  its  combination 
with  oxide  of  lead. 

CURD.  The  coagulum  which  sepa- 
rates from  milk,  upon  the  addition  of 
acid,  rennet,  or  wine. 

CURRENTS,  ATMOSPHERIC.  Dis- 
turbances of  the  atmospheric  mass  from 
regular  or  accidental  causes.  1.  Regular 
or  periodical  currents  are  the  trade-winds, 
monsoons,  sea  and  land  breezes,  which 
are  caused  by  the  rotatory  motion  of  the 
globe  being  greater  than  that  of  the  air, 
by  the  combined  attraction  of  the  sun 
and  moon  producing  tides  in  the  atmo- 
sphere, &c.  2.  Irregular  currents  are 
ordinary  winds,  produced  by  variations 
of  temperature  or  of  electrical  distribu- 
tion, and  have  frequently  a  circular  or 
rotatory  motion. 

CURRENTS  OF  THE  SEA.  Certain 
motions  of  the  sea,  which  are  independent 
of  the  tides,  and  named  drift- currents 
and  stream-currents. 

1.  Drift-currents  are  motions  produced 
on  the  surface  of  the  sea  by  the  perpetual 
or  the  prevailing  winds.  Thus,  in  the 
Atlantic  Ocean,  a  drift-current  occurs 
between  the  tropics,  where  it  is  produced 
by  the  trade-wind;  other  drift-currents 
occur  to  the  north  and  the  south  of  30°, 
where  they  are  ascribed  to  the  effects  of 
the  prevalent  winds. 

2.  Stream-currents  are  motions  pro- 
duced to  a  great  depth,  perhaps  to  the 
bottom,  of  the  sea ;  their  causes  are  con- 
sequently unknown.  Amongst  these 
may  be  noticed  the  equatorial  current, 
running  from  the  coast  of  Africa  to  that 
of  South  America;  and  the  gulf-stream, 
flowing  from  North  America  to  the  shores 
of  Europe. 

CURRENTS,  SUBTERRANEAN. 
Subterranean  currents  of  water,  sup- 
posed to  be  the  cause  of  the  formation  of 
caverns  in  limestone  districts  by  gra- 
dually wearing  away  the  rock  in  the 
course  of  fissures. 

CURSO'RES  (cursus,  a  course).  Cours- 
ers ;  an  order  of  birds,  so  named  from 
their  remarkable  velocity  in  running. 
They  were  included  by  Cuvier  in  the 
Grallatoreg,  or  Waders,  probably  on  ac- 
count of  the  length  of  their  legs.  They 
comprise  the  ostrich,  the  cassowary,  the 
emu,  the  apterix,  and  the  dodo.  These 
birds  exhibit  the  nearest  approach  to 
the  Mammalia.  [Under 

97 


Under  the  term  Cur  sores,  Walcknaer 
arranges  those  spiders  which  make  no 
webs,  but  catch  their  prey  by  swift 
pursuit. 

CURSO'RIA  {cursus,  a  course).  A 
family  of  Orthopterous  insects,  the  legs 
of  which  are  all  alike,  and  adapted  for 
running.  They  include  the  ear-wig,  the 
cockroach,  and  the  mantis.  See  Sana- 
toria. 

CU'RTATE  (curtatus,  shortened).  A 
term  sometimes  applied,  in  Geometry  or 
Astronomy,  to  a  line  projected  ortho- 
graphically  upon  a  plane. 

Curtate  Distance,  in  Astronomy,  de- 
notes a  planet's  distance  from  the  sun, 
reduced  to  the  plane  of  the  ecliptic. 

CURVE  {curvus,  bent).  A  term  ap- 
plied to  a  line  of  which  no  portion,  how- 
ever small,  is  straight.  A  crooked  line 
may  be  either  a  curved  line,  or  the  junc- 
tion of  two  or  more  straight  lines  drawn 
in  different  directions.  The  principal 
curves  are  the  circle,  the  ellipse,  the 
parabola,  the  hyperbola,  and  the  cycloid. 

1.  Curve,  Algebraic  and  Transcendental. 
1.  Algebraic  curves  are  those  in  which 
the  relation  between  the  abscissa  and  the 
ordinate  is  expressed  by  an  algebraic 
equation.  2.  Transcendental  curves  are 
those  in  which  the  relation  between  x 
and  y  is  not  expressed  by  an  algebraic, 
but  by  a  differential  equation  ;  that  is,  by 
an  equation  between  dx  and  dp. 

2.  Curve,  Evolute  and  Involute  of.  If 
a  thread,  having  one  of  its  ends  fixed,  be 
wound  round  a  curve,  this  primary  curve 
is  called  the  evolute.  If  the  thread,  thus 
tightly  applied  upon  the  convexity  of  the 
curve,  be  then  unwound,  it  will  describe 
a  secondary  curve  at  the  back  of  the 
former,  termed  the  involute.  It  will  be 
seen  that  the  thread,  at  every  point  of 
unwinding,  is  a  tangent  to  the  evolute. 

3.  Curve,  Equation  of.  An  algebraic 
expression,  pointing  out  the  relation  be- 
tween the  ordinate  and  the  abscissa.  In 
every  conic  section,  these  two  lines  are  at 
right  angles  to  each  other ;  and  at  what- 
ever point  of  the  axis  (in  the  same  sort 
of  curve)  the  ordinate  may  be  drawn, 
these  two  lines  will  always  have  the  same 
relation  to  each  other. 

4.  Curves  of  Double  Curvature.  Curves 
traced  on  surfaces  which  are  not  plane :  a 
double  curvature  thus  arises,  viz.  that 
belonging  to  the  line  itself,  and  that  of 
the  surface  on  which  it  is  traced. 

5.  Curve  Surfaces.  A  curve  surface 
is  represented  algebraically  by  an  equa- 
tion containing  three  variables,  as  x,  yt 

F 


CYC 


CYC 


and  z.  It  is  geometrical  when  its  equation 
is  algebraic,  and  expressed  in  finite  terms ; 
and  mechanical,  when  the  equation  is 
not  algebraic,  but  differential. 

CUS  P  (cuspis,  a  point).  In  Geometry, 
the  point  where  two  parts  of  a  curve 
meet  and  terminate.  In  Astronomy  it 
denotes  the  tip  or  horn  of  the  crescent 
of  the  moon.  In  an  eclipse  of  the  sun, 
the  borders  of  the  sun  and  moon  make 
two  cusps  at  their  point  of  intersection. 

CU'SPIDATE  {cuspis,  a  spear).  Spear- 
shaped;  tapering  to  a  stiff  point;  ab- 
ruptly acuminate;  a  term  applied  to 
leaves. 

CUTICLE  (dim.  of  cutis,  skin).  In 
Botany,  a  thin  homogeneous  membrane, 
external  to  the  epidermis,  formed  of  or- 
ganic mucus,  and  overlying  every  part 
of  plants,  except  the  stomates  and  the 
stigmatic  tissue. 

CY'ANIC  ACID.  A  volatile,  corrosive 
acid,  procured  from  cyanogen,  existing 
only  in  combination.  It  is  converted 
spontaneously  into  a  white  solid  matter 
called  cyamelide. 

CY'ANITE  (nvavos,  blue).  Disthene. 
A  mineral  occurring  in  the  granite  and 
mica- slate  of  primitive  mountains,  and 
used  in  India  as  an  inferior  kind  of  sap- 
phire. Its  principal  colour  is  Berlin- 
blue,  which  passes  into  grey  and  green. 

CY'ANO-  (Kvavov,  blue).  A  Greek 
term,  denoting  a  clear  bright  blue  colour. 

CYAN'OGEN  {nvavos,  blue,  yewda,  to 
generate;  so  called  from  its  being  an 
essential  ingredient  in  Prussian  blue). 
Bi-carburet  of  nitrogen ;  a  gas.  It  forms, 
with  oxygen,  the  cyanic,  cyanous,  and 
fulminic  acids;  and  with  hydrogen,  the 
hydro-cyanic,  or  prussic.  All  its  com- 
pounds, which  are  not  acid,  are  termed 
cyanides  or  cyanurets. 

CYANO'METER  {nvavo?,  blue,  fxerpov, 
a  measure).  An  instrument  invented  by 
Saussure,  for  comparing  the  different 
shades  of  blue  in  order  to  determine  the 
deepness  of  the  tint  of  the  atmosphere. 

CY'ATHIFORM  (cyathus,  a  drinking- 
cup,  forma,  likeness).  Cup-shaped;  as 
applied  to  the  form  of  certain  corollas. 

CYCADA'CEjE.  A  family  of  Gymno- 
spermous  plants,  named  from  the  genus 
cycas,  and  consisting  of  trees,  with  a 
cylindrical  trunk,  increasing  by  a  single 
terminal  bud. 

CYCLE  {kukXov,  a  circle).  A  certain 
period  of  time,  in  which  the  same  revolu- 
tions begin  again ;  a  periodical  space  of 
time. 

1.  Cycle  of  the  Sun.    A  revolution  of 


twenty-eight  years,  at  the  expiration  of 
which  the  days  of  the  months  return 
again  to  the  same  days  of  the  week;  the 
sun's  place  to  the  same  signs  and  degrees 
of  the  ecliptic  on  the  same  months  and 
days,  so  as  not  to  differ  one  day  in  100 
years ;  and  the  same  order  of  Leap-years 
and  of  Dominical  Letters  returns ;  hence 
it  is  also  called  the  Cycle  of  the  Sunday 
Letter. 

2.  Cycle  of  the  Moon.  A  revolution  of 
nineteen  years,  after  which  the  various 
aspects  of  the  moon  are,  within  an  hour, 
the  same  as  they  were  on  the  same  days 
of  the  month  nineteen  years  before.  This 
cycle  was  adopted  on  the  16th  of  July, 
b.c.  433,  by  Meton,  whose  name  it  also 
bears. 

3.  Cycle,  Paschal.  The  cycle  of  the 
Sun  consists  of  twenty-eight,  and  the 
cycle  of  the  Moon  of  nineteen  years; 
these  cycles,  multiplied  by  each  other, 
form  a  third,  which  is  called  the  Paschal 
Cycle,  because  it  serves  to  ascertain  when 
Easter  occurs.  At  the  end  of  a  revolu- 
tion of  532  years,  the  two  Cycles  of  the 
Moon,  the  Regulars,  the  Keys  of  the 
Moveable  Feasts,  the  Cycle  of  the  Sun, 
the  Concurrents,  the  Dominical  Letters, 
the  Paschal  Term,  Easter,  the  Epacts, 
with  the  New  Moons,  recommence  as 
they  were  532  years  before,  and  continue 
the  same  number  of  years. 

4.  Cycle,  Ecliptical.  An  unknown  pe- 
riod of  time  during  which  the  angle  be- 
tween the  ecliptic  and  the  equator,  con- 
stituting the  obliquity  of  the  ecliptic,  has 
completed  all  its  changes.  The  present 
rate  of  diminution  of  the  obliquity  is 
estimated  at  about  48  seconds  of  a  degree 
every  century. 

CY'CLICA  (ki5k\oc,  a  circle).  A  section 
of  Coleopterous  insects,  with  bodies  of 
a  rounded  or  oval  form.  According  to 
Latreille,  they  constitute  a  subsection  of 
the  section  Tetramera. 

CY'CLIN^E.  A  sub-family  of  the 
Tellinidae,  or  Solid  and  Closed  Bivalves, 
named  from  the  genus  cyclas ;  these 
animals  are  generally  fluviatile,  and  have 
their  shells  covered  by  an  epidermis. 

CY'CLOBRANCHIA'TA  {kvk\o*,  a 
circle,  /3pa7x*a,  gills).  An  order  of  Gas- 
teropods,  in  which  the  branchia  form  a 
fringe  around  the  body  of  the  animal, 
between  the  edge  of  the  body  and  the 
foot.  The  order  consists  principally  of 
the  limpets. 

CYCLO-GANGLIATA  (riicXo?,  a  cir- 
cle, fayyXiov,  a  nerve-knot).  A  term 
applied  by  Dr.  Grant  to  the  fourth  sub- 


CYL 


C  YP 


kingdom  of  animals,  or  Mollusca,  com- 
prising animals  distinguished  by  the 
high  development  of  the  cerebral  ganglia, 
and  their  circular  distribution  around  the 
oesophagus.  These  are  the  Heterogan- 
gliata  of  Owen . 

CYCLO-NEURA  {kvk\os,  a  circle,  vev- 
pov,  a  nerve).  A  term  applied  by  Dr. 
Grant  to  the  first  sub-kingdom  of  ani- 
mals, or  Radiata,  as  expressive  not  only 
of  the  common  circular  form  of  the 
nervous  axis  in  this  division,  but  also  of 
its  rudimental  state  of  simple  filaments. 

CY'CLOID  (kvkXo?,  a  circle,  eidor, 
likeness).  A  geometrical  transcendental 
curve,  described  by  a  point  in  the  circum- 
ference of  a  circle,  which  rolls  along  a 
plane  until  it  has  completed  a  revolu- 
tion. Thus  the  nail  on  the  felly  of  a 
wheel  moves  in  a  cycloid,  as  the  carriage 
goes  along,  and  as  the  wheel  itself  both 
turns  round  its  axle  and  is  carried  along 
the  ground. 

When  the  tracing  point  is  placed  with- 
out the  circle,  the  curve  has  its  base 
shortened,  and  is  called  the  curtate  or 
contracted  cycloid.  If  the  point  is  within 
the  circumference,  the  curve  is  called 
the  prolate  or  inflected  cycloid. 

CYCLO'SIS  {kvkXo?,  a  circle).  A  cir- 
cular movement  of  the  globular  particles 
of  the  sap,  as  observed  in  the  cells  of 
Chara  and  Nitella,  and  in  the  jointed 
hairs  projecting  from  the  cuticle  of 
several  other  plants.  A  similar  motion 
has  been  recently  found  by  Mr.  Lister  to 
exist  in  a  great  number  of  Polypiferous 
Zoophytes. 

CYCLO'STOMI  (KwcXor,  a  circle,  <rr6- 
fia,  a  mouth).  An  order  of  Chondropte- 
rygious  or  Cartilaginous  Fishes,  having  a 
round  fleshy  lip,  by  which  they  adhere  to 
their  prey,  obtaining  their  food  by  suction, 
as  in  the  lamprey.  The  lip  is  supported 
by  a  cartilaginous  ring,  formed  by  the 
union  of  the  jaw-bones.  In  fishes  of  this 
order  the  vertebrated  structure  is  found 
in  Us  lowest  form. 

CYGNUS.  The  Swan  ;  a  northern  con- 
stellation containing  eighty-one  stars,  the 
principal  of  which  is  Dereb  Adige. 

CY'LINDER  {Kvhtvdpos,  a  cylinder). 
A  geometrical  solid,  with  a  circular  base, 
described  by  the  revolution  of  a  right- 
angled  parallelogram  about  one  of  its 
sides,  which  remains  fixed.  It  is  a  cir- 
cular prism,  as  a  cone  is  a  circular  pyra- 
mid. The  axis  of  a  cylinder  is  the  fixed 
straight  line  about  which  the  parallelo- 
gram revolves.  When  the  base  is  ellip- 
tical, the  solid  is  a  cylindroid ;  when  the 
99 


sides  are  perpendicular  to  the  base,  it  is 
aright  cylinder  or  cylindroid;  in  other 
cases  it  is  an  oblique  cylinder. 

CYLINDRE'NCHYMA  (kuXiv3Poc,  a 
cylinder,  ejxvH<*i  infusion).  A  designa- 
tion given  by  Morren  to  the  cylindrical 
variety  of  the  parenchyma  of  plants. 

CYM'BIFORM  (cymba,  a  boat,  forma, 
likeness).  Navicular,  or  boat-shaped,  as 
applied  to  the  glumes  of  certain  grasses, 
and  synonymous  with  carinate. 

CYME.  A  form  of  inflorescence  re- 
sembling an  umbel  and  a  corymb,  but 
with  a  centrifugal  expansion,  indicated 
by  the  presence  of  a  solitary  flower  in 
the  axis  of  the  dichotomous  ramifications. 

CY'MOPHANE.  The  designation 
given  by  Haiiy  to  chrysoberyl. 

CY'MOSE.  Resembling  a  cyme,,  as 
applied  to  inflorescences  and  leafy 
branches. 

CYNARA'CEiE.  A  division  of  the 
Compositce,  named  from  the  genus  cy- 
nara,  and  comprising  plants  charac- 
terized by  intense  bitterness,  which  de- 
pends upon  the  mixture  of  extractive 
with  a  gum  which  is  sometimes  yielded 
in  great  abundance. 

CYNA'RRHODON.  In  Botany,  an 
aggregate  fruit,  consisting  of  distinct 
ovaries ;  the  pericarps  are  hard,  inde- 
hiscent,  enclosed  within  the  fleshy  tube 
of  a  calyx,  as  in  rose,  calycanthus,  &c. 
The  term  is  a  Greek  compound  for  dog-rose. 
CYNI'PIDjE  (cynips,  the  gall-fly). 
The  Gall-flies ;  a  family  of  the  entomo- 
phagous  Terebrantia,  which,  by  means 
of  their  ovipositor,  form  tumors  on  plants, 
commonly  termed  galls,  nut-galls,  or  gall 
apples. 

CYPERA'CE^E.  The  Sedge  tribe  of 
Monocotyledonous  plants,  named  from 
the  genus  cyperus.  These  plants  re- 
semble grasses  in  appearance,  but  have  a 
solid  and  angular  stem,  without  a  dia- 
phragm at  the  articulations ;  the  flowers 
grow  in  the  axil  of  a  single  bract ;  and  the 
cotyledonar  extremity  of  the  embryo  is 
enclosed  within  the  albumen.  See  Gra- 
minacecs. 

CYPHE'LLjE  (icv<pe\\a,  the  hollows  of 
the  ears).  Pale  tubercle-like  spots  on  the 
under  surface  of  the  thallus  of  lichens,  as 
in  sticta. 

CY'PHER  or  CIPHER.  In  common 
language,  to  cypher  is  to  calculate ;  and 
to  write  in  cyphers  is  to  write  in  secret  or 
unknown  characters,  such  as  were  the 
Arabic  numerals  when  first  introduced 
into  Europe. 

CYPRiE'IDiE.  The  Cowries  or  Por- 
F2 


DAM 


DAT 


celain  shells ;  a  family  of  carnivorous 
Gasteropods,  named  from  the  typical  ge- 
nus cyprcea ;  the  shells  are  without  any 
spire,  the  last  whorl  enveloping  all  the 
others,  as  in  the  bullas. 

CYPRI'NIDjE  (cyprinus,  the  carp). 
The  Carp  tribe;  a  family  of  Malaco- 
pterygious  or  soft-spined  fresh-water 
fishes,  having  the  ventral  fins  placed  be- 
neath the  abdomen. 

C  Y'PS  EL  A  (Kvyj/e\ti,  any  hollow  vessel). 
In  Botany,  the  compound  fruit  of  the 
Compositae.  It  is  one-celled,  one-seeded, 
indehiscent,  with  the  integuments  of  the 
seed  not  cohering  with  the  endocarp  ;  in 
the  ovarial  state  evincing  its  compound 
nature  by  the  presence  of  two  or  more 
stigmata ;  but  nevertheless  unilocular, 
and  having  but  one  ovulum. 

CY'PSELIN^E  (cypselus,  a  swift). 
Cypseline  Birds,  or  Swifts ;  a  group  of 
Macgillivray's  Volitatrices  or  Gliders, 
remarkable  for  the  extreme  rapidity  of 
their  flight  and  unwearied  activity. 

CYSTIBRA'NCHIANS  (tfrrit,  a  blad- 
der, /?pct7x<a,  gills).     A  family  of  Isopo- 


dous  Crustaceans,  comprising  those 
which  have  the  branchiae  lodged  in  vesi- 
cular cavities. 

CY'STICA  {km™,  a  bladder).  Cyst- 
worms  or  hydatids ;  an  order  of  Entozoa, 
which  have  one  or  more  buccal  orifices 
leading  into  a  terminal  cyst. 

CYSTFDIUM  (dim.  of  avari?,  a  blad- 
der). In  Botany,  a  term  employed  by 
Link  as  synonymous  with  utricle.  By 
the  term  cystidia  are  denoted  the  pro- 
jecting cells,  or  supposed  male  organs  of 
agarics,  &c. 

CY'STULA  or  CISTELLA.  A  round 
closed  apothecium  in  lichens,  filled  with 
sporules  adhering  to  filaments  arranged 
round  a  common  centre,  as  in  sphaero- 
phoron.  The  term  is  also  applied  to  the 
little  open  cups  on  the  upper  surface  of 
the  fronds  in  marchantia. 

CYTOBLAST  (kvtov,  a  cavity,  /3\a- 
ardvoi,  to  sprout).  A  nucleus  observed  in 
the  centre  of  some  of  the  bladders  of  the 
cellular  tissue  of  plants,  and  regarded 
by  Schleiden  as  a  universal  elementary 
organ. 


D 


DACTYLO'LOGY  (ddnTi/Xof,  a  finger, 
Ao-yor,  an  account).  The  art  of  spelling 
words  by  placing  the  fingers  in  such 
positions  as  to  signify  the  letters  of  the 
alphabet.  Dactylology  is  to  alphabetic 
writing  what  this  is  to  speech. 

DAGUERRE'OTYPE.  A  process  by 
which  all  images  produced  by  the  camera 
obscura  are  retained  and  fixed  in  a  few 
minutes  upon  surfaces  of  silver,  by  the 
action  of  light.  The  name  is  derived 
from  Daguerre,  the  inventor. 

D'ALEMBERT'S  PRINCIPLE.  A 
principle  in  Mechanics,  which  may  be 
thus  stated: — "If  several  non-elastic 
bodies  have  a  tendency  to  motion,  with 
velocities,  and  in  directions  which  they 
are  constrained  to  change,  in  consequence 
of  their  reciprocal  action  on  each  other, 
then  these  motions  may  be  considered  as 
composed  of  two  others ;  one,  which  the 
bodies  actually  take ;  and  the  other  such, 
that,  had  the  bodies  been  acted  on  by 
such  alone,  they  would  have  remained  in 
equilibrium." 

DAMPS.  The  permanently  elastic 
fluids  which  are  extricated  in  mines. 
These  are  choke  damp,  or  carbonic  acid ; 
100 


and  fire  damp,  consisting  almost  solely 
of  light  carburetted  hydrogen,  exploding 
on  contact  with  a  light. 

DAOU'RITE.  Rubellite.  A  variety 
of  red  schorl  found  in  Siberia,  mixed 
with  white  quartz. 

DASY'METER  (3a<w,  dense,  nerpov, 
a  measure).  A  measurer  of  density;  an 
instrument  employed  for  testing  the 
density  of  the  air.  It  is  used  for  this 
purpose  instead  of  a  barometer,  and  is 
sometimes  called  a  manometer. 

DA'TA.  Things  given.  A  term  used 
in  Geometry  to  denote  certain  things 
or  quantities,  which  are  either  actually 
exhibited,  or  can  be  found  out;  that  is, 
which  are  either  known  by  hypothesis,  or 
can  be  demonstrated  to  be  known. 

DA'THOLITE.  A  mineral  found  in 
Norway,  containing  boracic  acid,  silica, 
and  lime.     See  Botryolite. 

DATIVE  CASE  (dativus,  from  do,  to 
give).  The  giving  case  of  nouns,  known 
by  the  signs  to  and  for,  and  serving  to 
denote  the  remoter  object  to  which  the 
action  of  the  subject  is  directed;  for 
which,  to  the  benefit  or  loss  of  which, 
something  is  done. 


DEC 


DEC 


DA'VITE.  A  fibrous  sulphate  of  alu- 
mina, found  in  a  warm  spring  near  Bo- 
gota in  Columbia. 

DAY.  In  common  language,  the  in- 
terval of  time  which  elapses  between  the 
rising  and  the  setting  of  the  sun  ;  this  is 
called  an  artificial  day. 

1.  The  civil  day  begins  at  twelve 
o'clock  at  midnight,  and  lasts  till  the 
same  hour  of  the  following  night.  It  is 
counted  in  two  portions  of  twelve  hours 
each,  viz.  from  midnight  to  noon,  and 
from  noon  to  the  succeeding  midnight. 

2.  The  astronomical  or  solar  day  begins 
at  noon,  and  is  counted  up  to  twenty-four 
hours,  terminating  at  the  succeeding 
noon.  This  mode  of  reckoning  the  day 
is  employed  in  the  Nautical  Almanac, 
and  may  lead  to  mistakes  with  persons 
not  familiar  with  this  mode  of  computa- 
tion. Thus,  January  10,  fifteen  hours,  in 
astronomical  time,  is  January  11,  three 
in  the  morning,  civil  time. 

3.  The  sidereal  day  is  the  time  which 
elapses  between  that  of  a  star  being  in 
the  meridian  of  a  place  to  the  moment 
when  it  arrives  at  the  meridian  again. 
This  period  is  always  the  same,  not  being 
affected  by  the  motion  of  the  earth  in  her 
orbit,  as  the  solar  day  is.  The  sidereal 
day  is  about  four  minutes  less  than  the 
mean  solar  day. 

DEBA'CLE  (debacler,  to  unbar,  to 
break  up  as  a  river  after  a  long  frost). 
A  great  rush  of  waters  which,  breaking 
down  all  opposing  barriers,  carries  for- 
ward the  broken  fragments  of  rocks,  and 
spreads  them  in  its  course. 

DE'CAGON  (3<?/«x,  ten,  yavia,  an 
angle).  A  geometrical  figure,  having  ten 
sides  and  consequently  ten  angles.  If 
the  sides  and  angles  are  all  equal,  the 
figure  is  a  regular  decagon,  and  may  be 
inscribed  in  a  circle. 

DECAGY'NIA  (deva,  ten,  ywrj,  a  wo- 
man). The  designation  of  those  orders 
of  plants  in  the  Linnaean  system,  which 
are  characterized  by  the  presence  of  ten 
pistils. 

DECA'NDRIA  (5<?<ca,  ten,  iv^p,  a 
man).  The  tenth  class  of  plants  in  the 
Linnaean  system,  characterized  by  the 
presence  of  ten  stamens. 

DECANTA'TION.  The  act  of  pour- 
ing off  clear  fluid  from  sediment,  or  from 
suspended  impurities,— a  method  some- 
times adopted  to  avoid  the  use  of  filters, 
which  might  be  destroyed  by  an  acid  or 
alkaline  solution. 

DECATODA  (3e«a,  ten,  ttou?,  ttoSop,  a 
foot).    The  highest  order  of  the  Crus- 
101 


tacea,  which  have  ten  ambulatory  feet, 
the  cephalic,  thoracic,  and  pro-abdominal 
segments  united,  and  the  branchiae  con- 
cealed under  the  sides  of  the  carapace,  as 
seen  in  the  astacus  fluviatilis. 

DECA'RBONIZA'TION.  The  process 
of  depriving  a  body  of  its  carbon ;  as  em- 
ployed, artificially,  for  converting  cast 
iron  into  malleable  iron ;  and,  in  nature, 
in  removing  the  superfluous  carbon  of 
the  seed  in  the  function  of  germination. 

DECI'DUOUS  {decido,  to  fall  off). 
Falling  off;  a  term  applied  to  any  thing 
which  falls  off  in  a  certain  stage  of 
growth,  as  the  terminal  whorls  of  the 
pupaform  land-shells,  the  petals  and  se- 
pals of  certain  flowers,  &c.  The  term  is 
synonymous  with  caducous,  and  opposed 
to  persistent,  which  denotes  permanence. 

DE'CIMAL  (decimus,  the  tenth).  A 
fraction  whose  denominator  is  10,  or 
some  power  of  10,  as  100,  1000,  &c.  In- 
stead, however,  of  writing  the  denomi- 
nator under  the  numerator,  as  in  vulgar 
fractions,  it  is  expressed  by  pointing  off, 
from  the  right  of  the  numerator,  as  many 
figures  as  there  are  cyphers  in  the  deno- 
minator ;  thus,  *2,  "23,  '127,  signify 
respectively  &  t&,  TooV 

DECLE'NSION  {declino,  to  deflect). 
In  Grammar,  the  deriving  of  the  cases 
of  nouns  from  one  another ;  the  changes 
of  termination  corresponding  to  the  vari- 
ous relations  in  which  the  subject  is  con- 
ceived to  stand. 

DE'CLINATE  (declino,  to  bend  down- 
wards). Bent  downwards  ;  as  applied  to 
the  stamens  of  plants  when  they  all  bend 
to  one  side,  as  in  amaryllis. 

DECLINATION  (declino,  to  bend). 
The  distance  from  the  equator  of  the 
parallel  described  by  a  star  ;  it  is  counted 
from  0  up  to  90  degrees,  and  is  austral 
or  southern,  boreal  or  northern,  in  refer- 
ence to  the  equator.  Declination  on  the 
celestial  globe  corresponds  with  latitude 
on  the  terrestrial;  and  the  parallels  of 
declination  are  similar  to  the  parallels  of 
latitude. 

1.  Declination  circles  are  small  circles 
of  the  sphere,  parallel  to  the  equator,  in 
which  the  stars  perform  their  apparent 
diurnal  revolution. 

2.  Declination  of  the  magnetic  needle 
is  the  angle  which  the  horizontal  needle 
makes  with  the  geographical  meridian  of 
any  given  place. 

DECOLLATED  (decollo,  to  behead). 
A  term  applied  to  those  univalve  shells 
in  which  the  apex  or  head  is  worn  off  in 
the  progress  of  growth. 

F3 


DED 


DEF 


DECOMPOSITION.  The  resolution 
of  a  body  into  its  component  parts,  either 
spontaneously  or  by  chemical  agency. 

DE'COMPOUND.  A  term  applied,  in 
Botany,  to  those  ramifications  of  plants 
which  are  variously  compounded,  as  to 
leaves  in  which  the  petiole  bears  second- 
ary petioles.  When  the  secondary  petioles 
are  divided  into  a  third  set,  such  leaves 
are  said  to  be  supradecompound. 

DE'CREMENT  {decrementum,  a  de- 
crease). A  term  used  in  Crystallography 
to  denote  a  deficiency  of  successive  layers 
of  molecules  in  a  crystal,  when  this  de- 
ficiency takes  place  in  any  regular  order. 
This  decrement  is  measured  by  the  edges 
of  the  defect  or  part  wanting  to  complete 
the  simple  or  primary  form ;  and  the  re- 
lation which  these  edges  bear  to  the  cor- 
responding edges  of  the  primary  form,  is 
called  the  law  of  the  decrement.  This  is 
invariably  found  to  be  a  simple  numerical 
ratio,  rarely  exceeding  the  number  six. 
The  planes  resulting  from  these  decre- 
ments are  called  secondary  planes,  and 
the  forms  bounded  by  secondary  planes 
are  secondary  forms. 

Decrements  in  breadth  are  those  in 
■which  each  lamina  has  only  the  height 
of  a  molecule,  so  that  their  whole  effect, 
by  one,  two,  three,  &c,  courses,  is  in  the 
■way  of  breadth.  Decrements  in  height 
are  those  in  which  each  lamina,  exceed- 
ing only  the  following  one  by  a  single 
course  in  the  direction  of  the  breadth, 
may  have  a  height  double,  triple,  quadru- 
ple, &c,  of  that  of  a  molecule:  this  is 
expressed  by  saying,  that  the  decrement 
takes  place  by  two  courses,  three  courses, 
&c.  in  height. 

DECREPITATION  (decrepo,  to  crac- 
kle, as  a  candle,  when  almost  entirely 
burnt).  The  crackling  noise  which  oc- 
curs when  certain  salts  part  with  their 
water  of  crystallization,  on  the  applica- 
tion of  heat,  and  fall  in  pieces. 

DECUMBENT  {decumbo,  to  lie  down). 
Lying  prostrate,  but  rising  from  the 
earth  at  the  upper  extremity,  as  applied 
to  the  directions  taken  by  plants. 

DECU'RRENT  (decurro,  to  run  down) 
Decursive.  Running  down ;  a  term  ap- 
plied, in  Botany,  to  leaves  which  are  pro- 
longed down  the  stem,  giving  it  a  winged 
appearance. 

DECUSSATION  (decusso,  to  cross  like 
an  X).  A  term  applied  to  parts  which 
cross  each  other,  as  leaves  on  a  stem, 
when  arranged  in  pairs  which  alter- 
nately cross  each  other. 

DEDUCTIVE  REASONING.  The 
102 


process  of  scientific  inquiry  by  which  we 
pursue  laws  into  their  remote  conse- 
quences, as  distinguished  from  inductive 
reasoning,  by  which  we  arrive  at  laws  or 
axioms  by  an  accumulation  of  facts. 

DE'FERENT  CIRCLE  (defero,  to 
carry  away).  In  the  Ptolemaic  system, 
a  circle  or  orbit  on  which  the  centre  of 
another  circle  or  orbit  is  carried  round. 
Thus,  the  earth's  orbit  is  a  deferent  on 
which  the  moon's  orbit  is  carried.  See 
Epicycle. 

DE'FINITE  TERM.  In  Logic,  a  term 
which  defines,  or  marks  out,  a  particular 
class  of  beings,  or  a  single  person,  as 
distinguished  from  an  indefinite  term, 
which  does  not  define  or  mark  out  an 
object.  Thus,  all  animals  are  rational, 
or  not-rational ;  the  former  is  a  definite, 
the  latter  an  indefinite  term.  Definite 
terms  are  positive,  indefinite  terms  are 
privative  or  negative. 

DEFINITION.  A  metaphorical  term, 
literally  signifying  the  "laying  down  a 
boundary,"  and  employed,  in  Logic,  to 
denote  "  an  expression  which  explains 
any  term,  so  as  to  separate  it  from  every 
thing  else,"  as  a  boundary  separates 
fields. 

A  definition  is  called  nominal,  when  it 
merely  explains  the  meaning  of  the  term ; 
real,  when  it  explains  the  nature  of  the 
thing ;  essential,  when  it  assigns  the  con- 
stituent parts  of  the  essence  or  nature ; 
accidental,  when  it  assigns  the  properties 
and  accidents  of  the  essence ;  physical, 
when  it  lays  down  the  real  parts  of  the 
essence  which  are  actually  separable ; 
metaphysical  or  logical,  when  it  lays  down 
the  ideal  parts  of  it,  which  cannot  be 
separated  except  in  the  mind. 

DEFLAGRATION  [defiagro,  to  be 
utterly  consumed  by  fire).  The  oxidation 
of  metals  by  mixing  them  with  nitrate  or 
chlorate  of  potash,  and  projecting  the 
mixture  into  a  red-hot  crucible. 

1.  Deflagrating  Mixtures.  These  are 
generally  made  with  nitre,  the  oxygen  of 
which  is  the  active  ingredient  in  pro- 
moting their  combustion. 

2.  Deflagrator.  The  name  given  by 
Dr.  Hare  to  a  very  effective  battery,  in 
which  the  plates  were  so  connected  to- 
gether as  to  admit  of  the  whole  being 
immersed  into  the  exciting  liquid,  or 
removed  from  it,  at  the  same  instant. 

DEFLE'CTION  (defiecto,  to  bend  off). 
The  distance  by  which  a  curve  departs 
from  another  curve  or  from  a  straight 
line;  or  any  effect  of  curvature  or  of 
discontinuous  change  of  direction ;  also, 


DEL 


DEN 


the  bending  of  a  ray  of  light  from  its 
rectilinear  course  towards  an  opaque  body 
in  its  immediate  neighbourhood.  See 
Diffraction. 

DEGLUBITRI'CES  {deglubo,  to  pull 
off  the  skin  or  rind).  Huskers  ;  the  name 
given  by  Macgillivray  to  an  order  of  birds 
which  remove  the  shell  or  husk  of  seeds 
in  their  bill,  before  swallowing  them. 
They  are  all  easily  recognized  by  their 
stout  conical  bill,  and  include  all  our 
small  finch-like  birds.  Most  of  them  have 
a  modulated  song,  which  is,  however, 
much  inferior  to  that  of  the  Cantatrices. 

DEGRADING  CAUSES.  A  term  ap- 
plied, in  Geology,  to  those  causes  which 
refer  to  the  dissolving  and  wearing  away 
of  the  elevated  parts  of  the  earth's  sur- 
face, and  the  carrying  of  these  parts 
down  into  lower  levels.  These  causes 
are  meteoric,  connected  with  the  atmo- 
sphere ;  fluviatile,  depending  on  rivers ; 
and  oceanic,  in  which  the  ocean  is  the 
immediate  agent. 

DEGREE,  MINUTE,  SECOND.  The 
circumference  of  every  circle,  whatever 
be  its  actual  dimensions,  is  usually  con- 
sidered as  consisting  of  360°  (degrees), 
each  of  which  is  divided  into  60' (minutes), 
each  of  these  again  into  60"  (seconds),  and 
so  on  to  thirds  ("'),  and  fourths  (""),  and 
fifths,  if  necessary,  each  term  being  a  six- 
tieth of  its  predecessor.  By  some  writers 
the  decimal  system  is  preferred. 

DEGREE,  IN  ALGEBRA.  The  de- 
gree of  an  algebraical  term  is  the  number 
of  letters  which  enter  into  it  as  factors  ; 
thus  x2y3  is  absolutely  of  the  fifth  de- 
gree, but  of  the  second  degree  with  re- 
gard to  x,  and  of  the  third  degree  with 
regard  to  y.  The  degree  of  an  equation 
is  the  power  of  its  highest  term ;  if  the 
index  of  this  term  be  4,  the  equation  is 
said  to  be  of  the  fourth  degree. 

DEHISCENCE  (dehisco,  to  gape).  A 
term  applied,  in  Botany,  to  the  sponta- 
neous separation  of  the  valves  of  the 
fruits  of  certain  plants,  for  the  discharge 
of  the  seeds ;  and,  in  Zoology,  to  the 
splitting  open  of  the  bag  which  contains 
the  eggs. 

DEINOTHE'RIUM  (deivov  Bnplov,  a 
terrible  beast).  A  fossil  genus  of  gigantic 
pachydermata,  characterized  by  the  down- 
ward projection  of  enormous  tusks  from 
the  loweir  jaw. 

DE'LIAN  PROBLEM.  A  celebrated 
problem,  proposed  by  the  oracle  at  Delos, 
and  known  to  geometers  as  the  duplica- 
tion of  the  cube. 

DELIQUESCENCE  {deliquesce,  to 
103 


melt  away).  The  property  of  certain 
salts  of  becoming  liquid  by  their  attract- 
ing moisture  from  the  atmosphere.  In 
Botany,  a  panicle  is  said  to  be  deli- 
quescent, when  it  is  so  much  branched 
that  the  primary  axis  disappears— seem- 
ing, as  it  were,  to  melt  away. 

DELPHI'NIDiE  (delphinus,  a  dol- 
phin). The  Dolphin  tribe ;  a  family  of 
the  cetaceous  Vertebrata,  distinguished 
from  the  Balaenidae,  or  Whale  tribe,  by 
the  relative  size  of  the  head  and  body  : 
in  the  former,  the  head  is  not  out  of  the 
usual  proportion ;  in  the  latter,  it  is  im- 
moderately large. 

DELPHI'NUS.  The  Dolphin ;  one  of 
the  old  Greek  constellations,  consisting 
of  eighteen  stars,  and  succeeding  Aquila 
in  the  heavens. 

DE'LTA  (3e\ra,  the  Greek  letter  A). 
A  term  applied  to  the  alluvial  land 
formed  by  a  river  at  its  mouth,  when  it 
divides,  before  entering  the  sea,  into 
separate  and  diverging  streams.  The 
term  was  first  applied  in  the  case  of  the 
Nile,  from  the  resemblance  of  the  alluvial 
land  to  the  form  of  the  Greek  letter  A, 
the  sea  forming  the  base  of  the  triangle ; 
but  geologists  employ  the  term  in  analo- 
gous cases,  without  reference  to  the  pre- 
cise shape. 

DE'LTOID  (deXroeidii?,  delta-shaped, 
triangular).  Shaped  like  the  Greek  letter 
A ;  a  term  applied  to  a  solid,  the  trans- 
verse section  of  which  has  a  triangular 
outline. 

DEMONSTRATION  (demonstro,  to 
point  out).  In  the  old  writers,  this  term 
signified  no  more  than  the  pointing  out 
the  connexion  between  a  conclusion  and 
its  premises,  or  that  of  a  phenomenon 
with  its  asserted  cause.  It  now  denotes 
a  necessary  consequence,  and  is  synony- 
mous with  proof. 

DEMOTIC  WRITING  (dnnoriMs,  of 
the  people).  A  mode  of  writing  in  com- 
mon use  among  the  Egyptians,  approach- 
ing very  nearly  to  the  Chinese  method. 
It  is  also  termed  the  epistolographic  and 
the  enchorial  style. 

DE'NEB.  An  Arabic  term  for  tail, 
generally  applied  to  the  bright  star  (/3)  in 
the  tail  of  Leo. 

DENOMINATOR.  An  arithmetical 
term,  employed  in  fractions,  to  denote 
the  number  of  parts  into  which  the  unit, 
or  integer,  is  divided.  The  other  part  of 
the  fraction,  or  the  numerator,  denotes 
how  many  of  these  parts  are  taken  to 
make  up  the  given  fraction. 

DE'NSITY  (densitas,  closeness).  A 
F4 


DEP 


DES 


term  relating  to  the  compactness  of 
bodies,  and  denoting  the  comparative 
quantity  of  matter,  in  different  bodies, 
which  is  contained  under  a  certain  bulk. 
As  gravity  is  understood  to  act  in  propor- 
tion to  the  relative  quantity  of  the  matter 
of  bodies,  their  specific  gravities  are  pre- 
sumed to  be  the  measure  of  their  densi- 
ties.    See  Rarity. 

DENTIRO'STRES  {dens,  a  tooth, 
rostrum,  a  beak).  A  group  of  the  In- 
sessores,  or  Perching  birds,  in  which  the 
horny  covering  of  the  upper  mandible  is 
notched  or  toothed  towards  the  point,  as 
in  the  shrikes,  the  thrushes,  the  warblers, 
the  chatterers,  and  the  fly-catchers. 

DENUDATION  {denudo,  to  make 
bare).  The  carrying  away,  by  the  action 
of  running  water,  of  a  portion  of  the 
solid  materials  of  the  land,  by  which  in- 
ferior rocks  are  laid  bare. 

DEONTO'LOGY  (8eov,  what  is  due, 
X670?,  an  account).  The  science  of  duty ; 
a  term  applied  by  the  followers  of  Ben- 
tham  to  their  system  of  ethics. 

DEOXIDA'TION.  The  separation  of 
oxygen  from  a  body ;  the  reducing  a  body 
from  the  state  of  an  oxide. 

DEPA'RTURE.  A  nautical  term,  de- 
noting the  number  of  miles  which  a  ship 
has  sailed  east  or  west;  but  more  spe- 
cifically defined  to  be  "  the  sum  of  all  the 
successive  elementary  meridian  distances, 
when  the  nautical  distance  is  assumed  to 
be  divided  into  an  indefinite  number  of 
equal  parts."    See  Nautical  Distance. 

DEPHLEGMA'TION.  The  chemical 
process  of  concentration,  by  depriving 
a  body  of  water.  By  phlegma  is  meant 
a  watery  distilled  liquor,  as  distinguished 
from  a  spirituous  liquor. 

DEPHLOGI'STICATED.  That  which 
is  deprived  of  its  phlogiston;  in  modern 
language,  that  which  is  oxidized.  The 
term  is  derived  from  the  old  theory  of 
combustion,  in  reference  to  which,  oxy- 
gen gas  was  called  dephlogisticated  air; 
and  chlorine,  dephlogisticated  marine 
acid.     See  Phlogiston. 

DEPRESSION,  ANGLE  OF.  The 
angle  by  which  a  line  drawn  from  the 
eye  to  any  object  dips  below  the  horizon. 

DEPRESSION,  IN  ALGEBRA.  The 
reduction  of  an  equation  to  a  lower  de- 
gree, by  dividing  both  sides  of  it  by  a 
common  measure. 

DEPRESSION  OF  THE  HORIZON. 
Dip  of  the  horizon.  In  Nautical  Astro- 
nomy, the  depression  or  dipping  of  the 
visible  horizon  below  the  true  horizontal 
plane,  owing  to  the  eye  of  the  observer 
104 


being  placed  above  the  level  of  the  sur- 
face of  the  sea. 

DERBYSHIRE  SPAR.  Fluor-spar, 
technically  called  blue- John  ;  fluate  of 
lime,  or  a  combination  of  calcareous  earth 
with  fluoric  acid,  found  abundantly  in 
Derbyshire. 

DEREB  ADIGE.  A  star  of  the  first 
magnitude  in  the  northern  constellation 
Cygnus. 

DERIVATION,  LAW  OF.  In  finding 
the  successive  differential  co-efficients 
of  a  power  of  x,  the  law  is,  to  get  the 
next  differential  co-efficient,  multiply  the 
last  by  its  exponent,  and  reduce  the  ex- 
ponent by  a  unit. 

DERIVATIVE  WORDS.  In  Gram- 
mar, these  are  words  either  compounded 
of  two  significant  words  in  the  language, 
or  of  one  significant  word  and  a  termina- 
tion which  modifies  its  meaning,  as 
schoolmaster,  scholar.  They  are  distin- 
guished from  primitive  words,  which  have 
no  derivation  in  the  language,  as  school. 

DERMA'PTERA  (depfxa,  skin,  Trre- 
p6v,  a  wing).  Ear-wigs;  an  order  of 
insects,  having  their  anterior  pair  of 
wings  coriaceous,  not  employed  in  flight  ; 
the  posterior  membranous,  only  partially 
covered  by  the  elytra. 

DERME'STIDiE  (dermestes,  from  dep- 
jua,  skin,  €<T0ioi,  to  eat).  Skin-eaters  ;  a 
family  of  Coleopterous  insects,  of  the  sec- 
tion Necrophaga  of  Macleay,  named  from 
the  genus  dermestes,  which  is  well  known 
for  its  ravages  on  the  preserved  skins  of 
animals. 

DE'RMOBRANCHIA'TA  (depfta, 
skin,  /3p<i7X'a>  gills)-  A  family  of  Gaste- 
ropods,  named  from  the  genus  dermato- 
branchus,  and  comprising  those  mollusks, 
which  respire  by  means  of  external  bran- 
chiae or  gills,  having  the  form  of  mem- 
branous plates,  filaments,  or  tufts. 

DE'RMOSKE'LETON  (d<?PMa,  skin, 
aae\erov,  skeleton).  The  hard  integu- 
ment which  covers  most  invertebrate, 
and  some  vertebrate  animals. 

DERO'SNE'S  SALT.  A  crystalline 
substance,  obtained  by  treating  opium 
with  ether,  and  also  termed  narcotine 
and  opiane.     „ 

DESCENDING  NODE.  That  point 
of  a  planet's  orbit,  where  it  cuts  the  eclip- 
tic, proceeding  southward,  marked  £S. 

DESCRIPTION.  In  Logic,  an  acci- 
dental definition,  or  that  which  assigns 
the  circumstances  belonging  to  the 
essence,  viz.  properties  and  accidents. 
See  Definition. 

DESPUMA'TION  {despumo,  to  scum). 


DEW 


DI  A 


Literally,  the  throwing  off  of  froth  or 
scum,  and  generally,  the  clarifying  of  a 
fluid,  or  the  separating  its  foul  parts. 

DESQUAMATION  {desquamo,  to  scale 
fishes,  to  bark  trees).  The  falling  off  of 
the  cuticle,  in  the  form  of  squamce  or 
scales. 

DETER'MINATE  PROBLEM.  A 
problem  which  admits  of  one  solution 
only,  or  of  a  limited  number  of  solutions ; 
as  distinguished  from  an  indeterminate 
problem,  which  admits  of  an  indefinite 
number  of  solutions. 

DETONATION  (detono,  to  thunder 
mightily).  Instantaneous  ignition,  ac- 
companied by  a  loud  noise  and  a  violently 
disruptive  force,  owing  to  the  sudden 
expansion  of  gas. 

DETRITUS  {de,  from,  tero,  to  rub). 
Matter  worn  or  rubbed  off  from  rocks, 
consisting  of  blocks  of  various  sizes, 
gravel,  sand,  and  clay. 

DEUTO-  (ikt/T€po9,  second).  A  prefix 
denoting  two,  or  double,  as  rfew^-oxide, 
having  two  degrees  of  oxidation  ;  deuto- 
chloride,  &c. 

DEUTOXIDE  (3euTepo?,  second).  A 
term  applied  to  a  substance  which  is  in 
the  second  degree  of  oxidation.  This  term 
is  often  used  to  denote  a  compound  of 
3  atoms  of  oxygen  with  2  of  metal,  as  in 
deutoxide  of  manganese,  of  lead,  &c. 

DEVELOPMENT.  In  Algebra,  the 
process  by  which  any  mathematical  ex- 
pression is  changed  into  another  of  equi- 
valent value  or  meaning,  and  of  more 
expanded  form. 

DEVONIAN  SYSTEM.  A  geological 
system,  comprising  the  old  red  sandstone, 
and  forming  the  material  of  the  grand 
and  rugged  mountains  which  fringe  many 
parts  of  our  Highland  coasts,  and  range, 
on  the  south  flank  of  the  Grampians, 
from  the  eastern  to  the  western  sea  of 
Scotland.  These  formations,  in  Devon- 
shire and  Cornwall,  abound  in  shells  and 
corals,  and  present  a  structure  which 
brings  them  into  a  mineralogical  com- 
parison with  our  older  slate  rocks. 

DEW.  The  moisture  insensibly  de- 
posited from  the  atmosphere  on  the  sur- 
face of  the  earth.  It  occurs  whenever 
that  surface  is  lower  in  temperature  than 
that  of  the  dew-point  of  the  atmosphere 
immediately  in  contact  with  it. 

DEW-POINT.  That  temperature  of 
the  atmosphere  at  which  its  moisture  be- 
gins to  be  precipitated.  By  some,  it  is 
called  the  point  of  saturation ;  by  Daniell, 
the  degree  of  "  the  constituent  tempera- 
ture of  atmospheric  vapour." 
105 


DEXIA'RLE.  A  family  of  Dipterous 
insects  of  the  section  Creophilae,  named 
from  the  genus  dexia,  and  subsisting 
chiefly  on  the  juices  of  flowers. 

DEXTRAL  {dexter,  the  right  hand). 
On  the  right  hand,  as  applied  to  the 
mouth  or  aperture  of  the  great  majority 
of  spiral  shells-,  when  the  mouth  is  on 
the  left,  it  is  said  to  be  sinistral  or  re- 
versed. No  generic  distinctions  can, 
however,  be  founded  on  this  character. 

DEXTRIN  {dexter,  the  right  hand). 
Mucilaginous  starch,  prepared  by  boil- 
ing a  solution  of  starch  with  a  few  drops 
of  sulphuric  acid.  Its  name  is  derived 
from  its  property  of  turning  the  plane  of 
the  polarization  of  light  to  the  right 
hand. 

DIA  {did).  A  Greek  preposition,  de- 
noting through.  Words  compounded 
with  6ia  imply  extension,  perversion, 
transition ;  also  that  which  in  English 
and  Latin  is  expressed  by  the  prefixes 
di-  or  dis-,  as  in  divido,  to  divide ;  dis- 
jungo,  to  disjoin. 

DIACAU'STIC  {6ta,  through,  Kavart- 
Kor,  burning).  A  term  applied  to  those 
caustic  curves,  which  are  formed  by  re- 
fraction, as  distinguished  from  the  cata- 
caustic  curve,  which  is  formed  by  reflec- 
tion.   See  Caustic  curve. 

DIACOU'STICS  {dtanova,  to  hear 
through).  That  branch  of  physics  which 
treats  of  the  properties  of  sound  refracted 
in  passing  through  media  of  different 
densities. 

DIACRITIC  MARKS  {dtcmptTiKos,  fit 
to  distinguish).  Marks  employed,  in 
Palaeography,  to  distinguish  letters  which 
are  similar  in  form ;  thus,  in  the  German 
running  hand,  the  letter  u  is  distin- 
guished by  the  superposition  of  the  mark 
"  from  the  letter  n. 

DIADE'LPHIA  {6k,  twice,  u6e\<p6?, 
a  brother).  The  seventeenth  class  of 
plants  in  the  system  of  Linnaeus,  cha- 
racterized by  the  union  of  the  filaments 
into  two  parcels,  or  brotherhoods.  See 
Adelphia. 

DIURESIS  {diatpeu,  to  divide).  A 
division  ;  a  grammatical  figure,  denoting 
the  division  of  one  syllable  into  two,  as 
siliice  for  silvce. 

DIAGO'METER,  ELECTRICAL {6id- 
yw,  to  conduct,  fserpov,  a  measure).  An 
apparatus  used  by  Rousseau  for  ascer- 
taining the  conducting  power  of  oil,  as 
a  means  of  defecting  its  adulteration.  It 
consists  of  one  of  Zamboni's  dry  piles, 
and  a  feebly-magnetized  needle,  moving 
freely  on  a  pivot.  The  deviation  of  the 
F5 


DI  A 


DI  A 


needle  is  less  in  proportion  to  the  low 
conducting  power  of  the  interposed  sub- 
stance. 

DIA'GONAL  (dia,  through,  ytavia,  an 
angle).  A  right  line  drawn  across  a 
quadrilateral  figure,  from  one  angle  to 
another;  by  some  called  the  diameter 
of  the  figure. 

DI'AGRAM  {bidypawxa,  a  figure  or 
plan).  A  mathematical  figure  of  any 
kind,  drawn  for  the  purpose  of  illustra- 
tion. 

DIAKE'NIUM.  The  term  by  which 
Richard  designates  the  fruit  of  the  Urn- 
belliferae,  from  its  consisting  of  two  ake- 
nia.    See  Achcenium. 

DIAL,  or  SUN-DIAL.  An  instrument 
for  determining  the  hour  of  the  day  by 
the  shadow  of  a  point  or  line  upon  a 
graduated  surface. 

DI'ALECT  (diaAeKTor,  discourse).  The 
language  of  a  country,  especially  that  of 
a  particular  district;  any  variety  of  a 
common  language. 

DIALECTICS  (dtaXe/cTiKor,  skilled  in 
argument).  In  Aristotle,  this  term  de- 
notes the  logic  of  probabilities,  as  op- 
posed to  strict  philosophical  argument. 
Plato  employed  it  as  synonymous  with 
metaphysics,  or  the  highest  philosophy. 
The  term  simply  means  "  the  art  of  con- 
versation," but  is  now  generally  applied 
to  the  practical  part  of  logic. 

DIA'LLAGE'  (dtaXXcryq,  difference). 
A  variety  of  augite,  generally  of  a  bronze 
yellow  colour,  possessing  the  most  perfect 
cleavage  in  the  direction  of  the  diagonal 
of  the  prism,  its  natural  joints  and  frac- 
tures exhibiting  a  very  different  lustre 
and  appearance. 

Diallage  Rock,  or  Euphotide.  An  orna- 
mental stone,  consisting  of  felspar  and 
diallage,  in  crystals  aggregated  together 
in  the  manner  of  granite.  The  diallage 
in  the  rock  is  called  gabbro. 

DIALU'RIC  ACID  {8ia,  through, 
olpovy  urine).  A  new  acid  produced,  in 
combination  with  ammonia,  by  the  de- 
composition of  alloxan  tin. 

DIA'METER  {dianerpea,  to  measure 
through).  A  straight  line  passing  through 
the  centre  of  a  circle,  and  terminating 
at  both  ends  in  the  circumference. 

Diameter,  transverse  and  conjugate. 
These  terms  are  applied  to  the  two  un- 
equal diameters  of  an  ellipse,  the  former 
to  the  longer,  the  latter  to  the  shorter, 
diameter.  They  are  also  termed  the 
greater  and  the  lesser  axis.  These  lines 
are  at  right  angles  to  each  other.  Any 
other  line  which  passes  through  the  cen- 
106 


tre  of  an  ellipse,  and  terminates  in  opp  o- 
site  points  of  its  circumference,  is  also 
said  to  be  a  diameter. 

DIAMOND.  A  brilliant  gem,  consist- 
ing of  carbon  in  its  highest  state  of 
purity.  Rose-diamonds  are  usually  cut 
out  of  the  octohedral  crystals  ;  brilliants, 
from  those  with  curvilinear  faces. 

DIA'NDRIA  (die,  twice,  uvtjp,  a  man ). 
The  second  class  of  plants  in  the  system 
of  Linnaeus,  characterized  by  the  presence 
of  two  stamens. 

DIAPA'SON  (S«i  iraawv,  through  all). 
In  Music,  the  interval  of  the  octave  ;  the 
compass  of  an  instrument  or  of  the 
voice,  a  term  signifying  the  same  as  con- 
cert-pitch. 

DIA'PHANOUS  {dia,  through,  0a/vw, 
to  show).  That  quality  of  a  substance 
which  renders  it  permeable  to  light. 
Translucent  is  a  more  common  term  of 
the  same  import.  Transparent  expresses 
more  than  translucent,  implying  not 
merely  the  admission  of  light  through 
the  substance,  but  the  vision  of  external 
objects.  The  terms  semi-translucent  and 
semi-transparent  denote  feebler  degrees 
of  these  qualities. 

DIAPHO'NICS  (dta,  through,  <p<avi], 
sound).  The  doctrine  of  refracted  sound. 
DI'ASPORE  (diaanopa,  dispersion). 
A  rare  mineral,  which  crackles  by  the 
heat  of  a  candle,  and  is  dispersed  in  mi- 
nute fragments. 

DI'ASTASE  (3ta'crra(7i9,  separation). 
A  vegetable  principle,  allied  in  its  general 
properties  to  gluten,  which  appears  in  the 
germination  of  barley  and  of  the  seed  of 
plants,  and  converts  their  starch  into 
gum  and  sugar  for  the  nutrition  of  the 
embryo.  The  name  is  derived  from  its 
property  of  separating  two  supposed  con- 
stituents of  starch. 

DIATHE'RMANOUS  (diaBepfxaiva,  to 
warm  through).  A  Greek  term  syno- 
nymous with  the  Latin  transcalent,  and 
denoting  the  free  permeability  of  a  sub- 
stance by  heat. 

Diathermancy.  The  property  possessed 
by  nearly  all  diathermanous  bodies,  of 
admitting  the  passage  only  of  certain  spe- 
cies of  calorific  rays.  When  the  quan- 
tity of  heat  transmitted  independently  of 
the  quality  is  to  be  denoted,  the  term 
diathermaneity  has  been  suggested  by 
Melloni,  in  order  to  preserve  the  same 
termination  as  in  the  word  diaphaneity, 
indicating  the  analogous  property  in  re- 
lation to  light. 

DIATO'NIC  SCALE  (dia.  through, 
tokos',  a  tone).    A  scale  of  music,  con- 


DIC 


DIF 


sisting  of  seven  intervals,  viz.  five  tones 
and  two  semitones. 

DIBO'THRIANS  (3ic,  twice,  j366piov, 
a  pit).  A  division  of  tape-worms,  includ- 
ing those  bothriocephallans  which  have 
only  two  fossae  or  pits  on  the  head. 

DIBRA'NCHIA'TA  (6ir,  twice,  fady 
Xta,  gills).  An  order  of  Cephalopods,  in 
which  the  branchiae  are  two  in  number, 
one  situated  on  each  side  of  the  body.  It 
embraces  all  the  ordinary  genera,  and  is 
subdivided  into  two  tribes,  viz.  the  deca- 
pods, which  have  the  eight  ordinary  arms 
and  the  two  longer  tentacula,  and  the 
octopods,  in  which  the  tentacula  are  ab- 
sent.    See  Tetrabranchiata. 

DFCERATES  (dif,  twice,  Kt?pa?,  a 
horn).  A  family  of  Gasteropods  which 
have  two  tentacula  on  the  head,  in  De 
Blainville's  arrangement.  The  diceras 
was  applied  by  Lamarck  to  a  fossil  genus 
of  bivalves. 

DICHO'TOMOUS  (3«Xa,  doubly,  Te>a>, 
to  divide).  A  term  applied  to  stems  or 
branches  which  bifurcate,  or  are  con- 
tinually divided  into  pairs.  Hence,  to 
dichotomize,  is  to  cut  into  two  equal  and 
similar  parts. 

DI'CHROISM  (3ip,  twice,  xpoijiia,  co- 
lour). In  Optics,  the  property  by  which 
a  crystallized  body  assumes  two  distinct 
colours  according  to  the  direction  in 
which  light  is  transmitted  through  them. 

DI'CHROITE.  A  mineral  consisting  of 
a  silicate  of  alumina  and  magnesia. 

DICLE'SIUM  (3tK\ip,  folding  two 
ways).  In  Botany,  a  collective  fruit, 
consisting  of  a  pericarp  indehiscent,  one- 
seeded,  enclosed  within  an  indurated 
perianth,  as  in  mirabilis. 

DI'COTYLE'DONS(dic,  twice,  kotvM- 
dwv,  a  seed-lobe).  A  grand  division  of 
the  vegetable  kingdom,  comprising  all 
those  plants  in  which  the  embryo  con- 
tains two  cotyledons  or  seed-lobes.  The 
dicotyledonous  embryo  coincides  with  the 
exogenous  development  of  wood,  and, 
hence,  Dicotyledons  and  Exogens  are  con- 
vertible terms. 

DICTUM  DE  OMNI  ET  NULLO. 
A  principle  established  by  Aristotle  as 
the  basis  of  his  logical  system,  viz.  "that 
whatever  is  predicated  (i.  e.  affirmed  or 
denied)  universally  of  any  class  of 
things,  maybe  predicated,  in  like  manner 
(viz.  affirmed  or  denied),  of  any  thing 
comprehended  in  that  class." 

DICTYO'PTERA  (SUtvov,  a  net,  me- 
pov,  a  wing).  An  order  of  insects,  com- 
prising the  cock-roaches,  in  which  the 
wings  are  four  in  number  when  they 
107 


exist;  but  they  are  generally  of  equal 
size,  and  never  folded. 

DIDA'CTYLE  (5i?,  twice,  baKrvXov,  a 
finger  or  toe).  Two-fingered,  or  two- 
toed  ;  as  applied  to  various  animals  which 
have  two  digits  on  their  extremities. 

DI'DYM  (3/au/io?,  twin).  The  name  of 
a  metal  recently  discovered  united  with 
oxide  of  cerium,  and  so  called  from  its 
being,  as  it  were,  the  /wi»-brother  of 
lantanium,  which  was  previously  found 
in  the  same  body. 

DIDYNA'MIA  (3i?,  twice,  bvvayn^, 
power).  The  fourteenth  class  of  plants 
in  the  system  of  Linnaeus,  characterized 
by  the  presence  of  four  stamens,  of  which 
two  are  long,  two  short.  This  condition 
occurs  in  the  natural  order  Labiatae. 

DIELE'CTRIC.  A  body  which  has 
the  power  of  transmitting  the  electric 
influences  through  itself,  —  a  property 
observed  in  the  most  perfect  non-con- 
ductors of  electricity,  whether  solid, 
liquid,  or  aeriform.    See  Induction. 

DIERESFLIS  {diaipeats,  separation). 
A  general  term  applied  by  Mirbel  to 
those  fruits  which  spontaneously  sepa- 
rate into  several  cocci,  when  ripe,  as  in 
the  mallow.  The  term  is  almost  syn- 
onymous with  carcerule. 

DI'FFERENCE.  DIFFERENTIA. 
In  Logic,  the  formal  or  distinguishing  part 
of  the  essence  of  a  species ;  in  common 
discourse,  it  is  the  characteristic ;  when 
necessarily  applicable,  it  is  a  property; 
when  contingently,  an  accident. 

DIFFERENTIAL  CALCULUS.  The 
term  differential,  in  the  higher  Mathe- 
matics, denotes  a  quantity  infinitely 
small,  or  less  than  any  assignable  magni- 
tude. The  object  of  the  differential  cal- 
culus is  to  find  the  ratios  of  the  differ- 
ences of  variable  magnitudes,  on  the 
supposition  that  these  differences  be- 
come infinitely  small.  It  agrees  with 
fluxions  in  every  respect  excepting  its 
notation  and  the  manner  of  its  expla- 
nation. 

DIFFERENTIAL  COEFFICIENT. 
In  analysis,  the  ratio  of  the  differential 
of  any  function  of  a  variable  quantity  to 
the  differential  of  the  variable. 

DIFFRA'CTION  OF  LIGHT  {dif- 
fringo,  to  break  in  pieces).  Inflexion  of 
light.  The  turning  of  light  from  a  recti- 
linear course  by  the  interposition  of  an 
opaque  body. 

DIFFUSION  OF  HEAT.  A  term 
expressive  of  the  modes  by  which  the 
equilibrium  of  heat  is  effected,  viz.  by  con- 
duction, by  radiation,  and  by  convection. 
F6 


DIG 


DICE 


DIFFUSION  VOLUME.  A  term 
adopted  to  express  the  different  dispo- 
sition of  gases  to  interchange  particles ; 
the  diffusion-volume  of  air  being  1,  that 
of  hydrogen  gas  is  3*83. 

Diffusion  Tube.  An  instrument  for 
determining  the  rate  of  diffusion  for  dif- 
ferent gases.  It  is  simply  a  graduated 
tube,  closed  at  one  end  by  plaster  of 
Paris,  a  substance,  when  moderately  dry, 
possessed  of  the  requisite  porosity.  The 
diffusion  of  gases,  as  thus  conducted, 
closely  corresponds  with  the  endosmosis 
of  liquids,  which  occurs  under  similar 
circumstances. 

DIGA'MMA.  Double  gamma.  In  some 
parts  of  Greece,  the  old  Greek  7  was  a 
kind  of  aspirate,  called,  from  the  way 
of  writing  it  (f),  digamma.  This  aspi- 
rate was  carried  by  the  Pelasgian  race 
into  Italy,  and  remained  in  Latin  as  a 
real  consonant  V,  vau.  It  supplies  the 
data  for  resolving  those  cases  of  metrical 
difficulty,  where  the  lengthening  of  a 
short  syllable  uniformly  takes  place  be- 
fore particular  words. 

DIGE'STER.  A  strong  vessel  of  cop- 
per or  iron,  with  an  air-tight  lid,  for 
preventing  the  loss  of  heat  by  evapo- 
ration. 

DIGE'STION  {digero,  from  diversim 
gero,  to  carry  into  different  parts).  In 
Physiology,  the  change  of  the  food  into 
chyme,  and  the  absorption  and  distribu- 
tion of  the  more  nutritious  parts,  or  the 
chyle,  through  the  system.  In  Chemistry, 
the  continued  action  of  a  solvent  upon 
any  substance. 

DIGESTIVE  SALT.  A  salt  discovered 
by  Sylvius,  since  named  muriate  of 
potash,  and  now  chloride  of  potassium. 

DI'GIT  {digitus,  a  finger).  An  old 
measure  of  a  finger's  breadth.  In  Astro- 
nomy, it  denotes  the  twelfth  part  of  the 
diameter  of  the  sun  or  moon,  and  is  used 
to  express  the  quantity  of  an  eclipse: 
thus  the  moon  is  said  to  be  six  digits 
eclipsed,  when  half  of  her  face  is  covered 
by  the  earth's  shadow.  In  Arithmetic, 
a  digit  is  any  symbol  of  number  from 
0to9. 

DI'GIT  ATE  {digitus,  a  finger).  A  term 
applied  to  that  kind  of  expansion,  in 
which  the  parts  are  spread  out  into 
finger-shaped  processes,  as  in  the  outer 
lip  of  the  scorpion  strombi. 

DIGITI'GRADA  {digitus,  a  toe,  gra- 
dior,  to  walk).  A  division  of  the  terres- 
trial Carnivorous  animals,  which  walk 
upon  their  toes,  and  bound  along  with 
considerable  elasticity  and  swiftness,  as 
10b 


the  weasel,  the  civet,  the  hyena,  and  the 
cat  tribes.     See  Plantigrada. 

DIGY'NIA  (5ir,  twice,  yvvt],  a  woman). 
The  name  of  those  orders  of  plants 
in  the  system  of  Linnaeus,  which  are 
characterized  by  the  presence  of  two 
pistils. 

DILE'MMA  {6i\t]nfxa,  a  double  pro- 
position ;  from  dk,  twice,  and  \afi- 
y8d»/a),  to  take).  In  Logic,  a  complex  kind 
of  conditional  syllogism,  having  more 
than  one  antecedent  in  the  major  pre- 
miss, and  a  disjunctive  minor.  In  other 
words,  it  is  a  complex  conditional  reasont 
ing,  in  which  either  one  of  the  antece- 
dents must  be  admitted,  or  one  of  the 
consequents  must  be  denied. 

The  expression,  horns  of  a  dilemma, 
relates  to  the  taking  hold  of  both  ways : 
if  a  person  is  not  caught  by  the  one 
antecedent  or  consequent,  he  must  be 
caught  by  the  other. 

DILU'VIUM  {diluo,  to  wash  away). 
Accumulations  of  gravel  and  loose  mate- 
rials, which  are  said  to  have  been  pro- 
duced by  the  action  of  a  diluvian  wave 
or  deluge  sweeping  over  the  surface  of 
the  earth. 

DIME'NSION.  In  Algebra,  a  term 
synonymous  with  degree ;  thus  x2y  is  of 
three  dimensions,  or  of  the  third  degree. 
In  Geometry,  length  is  of  one  dimension, 
surface  of  two,  solidity  of  three;  hence, 
geometry  of  three  dimensions  is  another 
term  for  solid  geometry. 

DI'MERA  (<J«p,  twice,  /xepo?,  apart). 
A  section  of  Homopterous  insects,  in 
which  the  tarsi  are  two-jointed,  as  in  the 
Aphidae. 

DIMO'RPHOUS  (3ir,  twice,  fxoP<prj, 
form).  A  term  applied  to  some  natural 
and  to  some  artificial  productions,  which 
occur  in  two  distinct  forms.  For  ex- 
ample :  arragonite  and  carbonate  of  lime 
are  chemically  the  same,  though  belong- 
ing to  different  primary  forms ;  and  the 
crystals  of  sulphate  of  nickel,  if  de- 
posited from  an  acid  solution,  are  square 
prisms;  but  if  from  a  neutral  solution, 
they  are  right  rhombic  prisms.  This 
property  of  assuming  two  incompatible 
forms,  is  called  dimorphism. 

DIMYA'RIA  (5i?,  twice,  /uv?,  a  mus- 
cle). A  general  name  for  those  bivalves 
whose  shells  are  closed  by  two  ad- 
ductor muscles  distinct  and  widely  re- 
moved from  each  other,  as  in  the  mussel. 
See  Monomyaria. 

DIOS'CIA  (3i?,  twice,  o'luot,  a  house). 
The  twenty-second  class  of  plants  in 
Linnaeus's  system,  in  which  the  stamens 


DIP 


DIP 


and  pistils  are  in  separate  flowers,  and  on 
separate  plants. 

DIOPHA'NTINE  PROBLEMS.  A 
species  of  problems,  in  which  it  is  re- 
quired to  solve  certain  questions,  the  an- 
swers to  which  shall  be  whole  numbers 
only.  They  are  found  in  a  treatise  on 
Algebra  by  Diophantus,  an  Alexandrian 
Greek,  who  lived  in  the  second  or  third 
century  of  the  present  era.  In  character 
they  closely  resemble  the  Hindoo  Algebra. 

DIO'PSIDE  (3<oV'«r,  a  view  through). 
A  mineral  which  may  be  considered  as 
the  type  of  the  augite  genus.  Several 
varieties,  differing  little  from  the  above, 
are  called  baikalite  and  fassaite,  names 
indicative  of  their  locality. 

DIO'PTASE.  Emerald  copper  ore;  a 
crystallized  silicate  of  copper,  found  in 
Siberia  and  the  Bannat. 

DIO'PTRICS  {dioirrpa,  an  optical  in- 
strument). That  branch  of  the  science 
of  Optics,  which  treats  of  the  refraction 
of  light,  when  it  passes  through  different 
media,  as  air,  water,  glass,  &c.  The  phe- 
nomena are  generally  referred  to  the  sub- 
ject of  refraction. 

DIO'SMEjE.  The  Buchu  tribe  of 
Dicotyledonous  plants.  Trees  and  shrubs 
with  leaves  exstipulate,  dotted ;  flowers 
axillary  or  terminal,  polypetalous,  her- 
maphrodite; stamens  hypogynous;  ova- 
rium many-celled ;  fruit  consisting  of 
several  concrete  capsules  ;  seeds  twin  or 
solitary. 

DIO'XIDE.  According  to  the  electro- 
chemical theory,  the  elements  of  a  com- 
pound may,  in  relation  to  each  other,  be 
considered  oppositely  electric;  the  equi- 
valents of  the  negative  element  may  then 
be  distinguished  by  Latin  numerals,  those 
of  the  positive  by  Greek ;  thus  a  bin- 
oxide  denotes  a  compound  which  con- 
tains two  equivalents  of  the  negative 
element  oxygen ;  whereas  a  rfi-oxide  in- 
dicates that  one  equivalent  of  oxygen  is 
combined  with  two  of  some  positive  body. 
And  so  of  6i-chloride,  di-chloride,  &c. 

DIP.  When  a  geological  stratum  does 
not  lie  horizontally,  but  is  inclhud,  it  is 
said  to  dip  towards  some  point  of  the 
compass,  and  the  angle  it  makes  with 
the  horizon  is  called  the  angle  of  dip  or 
inclination. 

DIP  OF  MAGNETIC  NEEDLE.  The 
angle  which  the  magnetic  needle,  when 
poised  so  as  to  move  freely  in  a  vertical 
direction,  makes  with  the  plane  of  the 
horizon.  It  is  more  scientifically  termed 
the  inclination  of  the  needle,  or  the  mag- 
netic inclination. 
109 


DIP  OF  SEA  HORIZON.  The  ap- 
parent angular  depression  of  the  visible 
horizon,  caused  by  the  position  of  the 
observer  above  the  surface  of  the  sea. 

DI'PHYDA  (dip,  twice,  <pv<a,  to  grow). 
A  group  of  the  Acalephce,  named  from 
the  genus  diphyes,  in  which  each  animal 
seems  to  consist  of  two  portions  so 
slightly  joined  together,  that  it  is  diffi- 
cult to  understand  their  connexion. 

DFPLOE'  (dinXon,  a  joining).  A  term 
applied  by  Link  to  the  parenchymatous 
substance  of  the  leaf,  which  lies  imme- 
diately beneath  the  two  surfaces.  See 
Mesophyllum. 

DI'PLO-GANGLIA'TA  (dtw\owt  dou- 
ble, yay/Xiov,  a  nerve-knot).  A  desig- 
nation of  the  Entomoida,  or  articulate 
animals,  which  have  *'  their  nervous 
columns  arranged  in  the  same  relative 
position  as  the  diplo-neura,  with  the  gan- 
glia increased  in  size,  and  corresponding 
with  the  increased  development  of  the 
segments  and  of  their  lateral  appen- 
dages."— Grant. 

DI'PLO-NEURA  {dnrXovs,  double, 
vevpov,  a  nerve).  A  designation  of  the 
Helminthoida,  comprising  the  various 
forms  of  Worms,  in  which  the  nervous 
columns  have  their  ganglionic  enlarge- 
ments very  slightly  developed,  and  are 
marked  by  a  greater  lateral  separation 
from  each  other  along  the  median  line, 
than  is  observed  in  the  next  sub-king- 
dom."— Grant. 

DIPLO'PTERA  (dtvXofc,  double,  tttc- 
pov,  a  wing).  A  group  of  aculeate  hy- 
menopterous  insects,  which  have  their 
upper  wings  folded  longitudinally,  when 
at  rest,  as  in  some  species  of  wasp. 

DIPLOTE'GIA  {dinkoZs,  double,  re- 
709,  a  covering).  In  Botany,  a  compound 
fruit,  differing  from  the  capsule  only  in 
being  adherent  to  the  calyx.  It  occurs 
in  campanula. 

DIPNEUMO'NEjE  (3ip,  twice,  7rve6- 
fivv,  a  lung).  A  section  of  spiders  which 
have  only  two  pulmonary  sacs. 

DIP  PEL'S  OIL.  An  animal  oil  pro- 
cured by  the  destructive  distillation  of 
animal  matter,  especially  of  albuminous 
and  gelatinous  substances. 

DI'PTERA  (3ip,  twice,  mepbv,  a 
wing).  An  order  of  insects  which  have 
only  one  pair  of  wings  fully  developed, 
and  these  are  on  the  mesothorax.  Instead 
of  posterior  wings,  there  are  pedunculated 
appendages,  called  halteres  or  poisers. 
The  mouth  contains  a  soft  proboscis,  of 
which  the  common  house-fly  affords  a 
familiar  instance.    See  Rhipiptera. 


DIS 


DIS 


DIPTEROCA'RPEjE.  The  Camphor- 
tree  tribe  of  Dicotyledonous  plants.  Trees 
abounding  in  resinous  juice ;  leaves  alter- 
nate; flowers  polypetalous;  stamens  hy- 
pogynous ;  carpella  concrete ;  calyx  tu- 
bular ;  fruit  coriaceous. 

DI'PTEROUS  (<3Jc,  twice,  mepov,  a 
wing).  Two-winged;  a  term  applied  to 
certain  seeds  which  have  their  margins 
prolonged  in  the  form  of  wings. 

DIPTERY'GIANS  (dit,  twice,  nrepi- 
ftov,  a  fin).  A  family  of  fishes  comprising 
those  which  have  only  two  fins. 

DIPY'RE  (6U,  twice,  irvp,  fire).  Leuco- 
lite.  A  silicate  of  alumina  and  lime,  found 
in  the  western  Pyrenees.  This  mineral 
derives  its  name  from  its  twofold  sus- 
ceptibility to  the  action  of  fire:  when 
heated  before  the  blowpipe,  it  first  be- 
comes phosphorescent,  and  then  fuses. 

DIRECT  AND  RETROGRADE.  As- 
tronomical terms  expressive  of  the  direc- 
tion in  which  the  heavenly  bodies  move. 
The  direct  course  is  from  west  to  east ; 
the  retrograde,  from  east  to  west.  These 
motions  are  otherwise  indicated,  the 
former  by  the  term  in  consequential  the 
latter  by  in  antecedentia. 

DIRECTION,  NUMBER  OF.  The 
number  of  days  after  the  22nd  of  March, 
including  both  days,  upon  which  Easter 
Sunday  takes  place. 

DIRECTIVE  FORCE.  A  term  em- 
ployed in  Magnetism  to  denote  the  ten- 
dency in  one  magnet  to  assume  a  par- 
ticular position  with  relation  to  another 
magnet. 

DIRE'CTRIX.  Linea  directrix.  A 
term  applied,  in  Conic  Sections,  to  a  line 
drawn  at  right  angles  to  the  axis  of  a 
parabola,  when  produced  to  a  certain 
point ;  and  this  point  is  equally  distant 
from  the  vertex  as  the  focus  of  the  curve. 

DISC  {blano?,  discus,  a  dish,  or  quoit). 
The  face  of  a  circular  plate ;  a  term  ap- 
plied to  the  apparently  plane  surface  of 
the  heavenly  bodies,  from  the  resem- 
blance of  this  surface  to  a  flat  round 
dish.  The  discus  of  the  ancients  was  a 
circular  piece  of  wood,  stone,  or  metal, 
used  in  their  games. 

DISCHARGER.  An  instrument  for 
discharging  a  jar  or  battery  of  its  elec- 
tricity. It  consists  of  two  bent  metallic 
rods,  each  of  them  terminating  at  one 
end  in  a  brass  knob,  and  connected  at 
the  other  end  by  a  joint,  which  is  fixed 
to  a  glass  handle. 

DISCO'BOLI  (dtV/cop,  a  disk,  /3d\\<o, 
to  throw).  A  family  of  Malacopterygious 
or  soft-spined  fishes,  in  which  the  ventral 
110 


fins  are  formed  into  a  disk  or  sucker,  by 
which  the  fish  is  enabled  to  attach  itself 
to  rocks  and  other  hard  substances. 

DI'SCOID  (dtanoeidv,  quoit-shaped). 
Circular  or  disk-shaped,  and  much  flat- 
tened, as  the  fresh-water  genus  planor- 
bis,  and  many  land-shells. 

DISCORD.  Dissonance.  In  Music,  a 
dissonant  and  inharmonious  combination 
of  sounds,  unless  treated  according  to 
the  rules  of  art. 

DISCOURSE.  Discursus.  In  Logic, 
an  operation  of  the  mind  commonly  called 
reasoning,  or  the  act  of  proceeding  from 
one  judgment,  to  another  founded  upon 
that  one,  or  the  result  of  it. 

DISCOVERY  OF  TRUTH.  There 
are  two  modes  of  discovering  truth. 
1.  The  one  is  by  Information,  and  it 
relates  to  matters  of  fact  previously 
unknown,  but  communicated  by  observa- 
tion and  testimony,  independent  of  all 
a  priori  reasoning.  2.  The  other  is  by 
Instruction,  and  it  relates  to  truths  which 
may  be  elicited  by  reasoning,  and  are 
therefore  implied  in  what  we  already 
know,  independent  of  observation  or 
testimony.  The  historian  informs,  the 
mathematician  and  the  moralist  instruct. 

DISCRETE  PROPORTION  (discre- 
tus,  separated).  An  arithmetical  propor- 
tion, in  which  the  ratio  of  the  antece- 
dents to  the  consequents  is  different  from 
the  ratio  of  the  consequent  of  the  first 
pair  of  terms  to  the  antecedent  of  the 
second,  as  in  2  \  3  .*  :  4  ;  6.  On  the 
other  hand,  a  continual  proportion  is 
that  in  which  the  ratio  of  every  contiguous 
pair  of  terms  is  the  same  throughout,  as 

in  2 : 4 : :  8 :  i6. 

DISCRETE  QUANTITY  (discretus, 
separated).  A  quantity  of  which  the 
component  parts  have  a  separate  and  dis- 
tinct existence :  numbers,  for  instance, 
are  discrete  quantities,  being  composed 
of  separate  units. 

DISJUNCTIVE.  A  logical  term  ap- 
plied to  a  proposition  which  consists  of 
two  or  more  categoricals,  so  stated  as  to 
imply  that  some  one  of  them  must  be 
true ;  e.  g.,  either  A  is  B,  or  C  is  D.  A 
syllogism  is  said  to  be  disjunctive,  the 
reasoning  of  which  turns  on  such  a  pro- 
position. 

DISK.  A  term  applied,  in  Botany,  to 
certain  bodies  or  projections,  situated  be- 
tween the  base  of  the  stamens  and  the 
base  of  the  ovary,  forming  part  with 
neither.  It  is  often  incorrectly  called 
nectary. 

DISPERSION  OF  LIGHT.    The  di 


DIS 


DI  V 


vision  of  a  ray  of  white  light  into  its  vari- 
ously coloured  component  rays,  as  seen 
upon  the  spectrum,  after  it  has  under- 
gone refraction  by  transmission  through 
a  prism. 

DISSE'PIMENT  {dissepio,  to  sepa- 
rate). Septum.  A  term  applied,  in  Bo- 
tany, to  the  partition  which  divides  a 
capsule  into  cells. 

DISTANCES,  LAW  OF.  A  curious 
law  observed  by  Professor  Bode,  of  Ber- 
lin— that  the  intervals  between  the  planet- 
ary orbits  go  on  doubling  as  we  recede 
from  the  sun,  or  nearly  so.  This  law  was 
interrupted  between  Mars  and  Jupiter, 
but  the  deficiency  was  afterwards  strangely 
supplied  by  the  discovery  of  four  new 
planets  in  that  very  interval,  revolving 
in  orbits  tolerably  well  corresponding 
with  the  law  in  question. 

DISTHENE.  Cyanite.  A  very  hard 
crystallized  mineral,  consisting  of  sub- 
silicate  of  alumina. 

DI'STICHOUS  (air,  twice,  <rT<'x°r»  a 
row).  Arranged  in  two  rows,  as  the 
florets  of  many  grasses ;  a  term  synony- 
mous with  bifarious. 

DISTILLATION  (distillo,  to  drop  by 
little  and  little).  The  vaporization  and 
subsequent  condensation  of  liquids,  by 
means  of  a  retort,  alembic,  or  still.  Dry 
distillation  is  performed  in  the  same 
way  as  the  humid,  except  that  the  sub- 
stance is  neither  immersed  nor  dissolved 
in  any  menstruum.  It  is  termed  sub- 
limation. 

Distillation,  Destructive.  The  process 
of  exposing  organized  substances,  or 
their  products,  to  distillation,  until  the 
whole  has  undergone  the  entire  effects  of 
the  furnace. 

DI'STOMA  (alp,  twice,  cro/ia,  the 
mouth).  Intestinal  worms  with  two 
pores, 

DISTRA'CTILE  (distraho,  to  draw 
apart).  In  Botany,  a  connective  which 
separates  into  two  unequal  portions,  the 
one  supporting  an  anther,  the  other  with- 
out an  anther,  as  in  salvia. 

DISTRIBUTED.  An  epithet  applied, 
in  Logic,  to  a  term  which  is  employed  in 
its  full  extent,  so  as  to  comprehend  all 
its  significates— every  thing  to  which  it 
is  applicable. 

DISTRIBUTION  OF  HEAT.  A 
term  expressive  of  the  several  ways  by 
which  the  rays  of  heat,  as  they  fall  upon 
the  surface  of  a  solid  or  liquid  body,  may 
be  disposed  of.  1.  They  may  be  reflected, 
or  rebound  from  the  surface ;  2.  they 
may  be  absorbed,  or  received  into  the 
111 


substance  of  the  body ;  or,  3.  they  may 
be  transmitted,  or  pass  directly  through 
its  substance.  In  the  first  and  third 
cases,  the  temperature  of  the  body  on 
which  the  rays  fall  is  entirely  unaffected ; 
in  the  second,  it  is  increased. 

DITHYRA  (dif,  twice,  06pa,  a  door). 
A  term  applied  by  Aristotle  to  the  bi- 
valved  mollusca,  or  those  which  have 
double  shells,  as  the  oyster  and  the 
cockle.  These  comprise  the  first  order 
of  Cuvier's  Acephala,  the  seventh  order 
of  his  Gasteropoda,  and  the  fifth  class  of 
his  Mollusca.    See  Monothijra. 

DIU'RNA  (diurnus,  daily).  A  desig- 
nation of  the  Butterfly  tribe  of  Lepido- 
pterous  insects,  from  their  habit  of  ap- 
pearing only  by  day.  They  are  distin- 
guished by  the  vertical  position  of  their 
wings  during  repose.  The  tribe  corre- 
sponds with  the  Linnaean  genus  Papilio. 

DIU'RNAL  MOTION  {diurnus,  daily). 
The  daily  revolution  of  the  earth  upon 
its  axis,  which  produces  day  and  night, 
and  causes  us  to  imagine  that  the  sun, 
planets,  and  stars,  move  round  the 
earth.    See  Axis. 

DIURNATION  (diurnus,  daily).  A 
term  introduced  by  Dr.  M.  Hall,  to  ex- 
press the  state  of  some  animals,  as  the 
bat,  during  the  day,  as  contrasted  with 
their  activity  at  night.    See  Hybernation. 

DIVA'RICATING  (divarico,  to  spread 
one  from  another).  Spreading  out  nearly 
at  a  right  angle  from  any  thing,  as 
branches  from  a  stem. 

DIVERGENT  RAYS.  Those  rays, 
which,  proceeding  from  a  point  of  the 
visible  object,  are  dispersed,  and  con- 
tinually depart  one  from  another,  in  pro- 
portion as  they  are  removed  from  the  ob- 
ject ;  in  which  sense  they  are  opposed  to 
convergent  rays. 

DIVERTICULUM.  The  Latin  term 
for  a  by-road,  and  hence  applied  to  a 
blind  tube  branching  out  from  the  course 
of  a  longer  one. 

DIVISIBILITY  (divido,  to  divide). 
The  property  by  which  bodies  are  capable 
of  being  separated  into  minute  parts. 
The  divisibility  of  matter,  though  mathe- 
matically illimitable,  is  closely  connected 
with  its  constitution,  and  must,  therefore, 
cease  with  the  ultimate  particles  of  which 
all  matter  is  supposed  to  consist. 

DIVI'SION.  In  Arithmetic,  the  me- 
thod of  finding  how  often  one  number  is 
contained  in  another,  i.  e.  how  often  one 
number  must  be  taken  to  make  up  an- 
other. Hence  Division  bears  the  same 
relation  to  Subtraction,  as  Multiplication 


DOK 


DOU 


bears  to  Addition.  In  Algebra,  the  sign 
-T-  placed  between  two  quantities  means 
that  the  former  of  those  quantities  is  to 
be  divided  by  the  latter :  thus  a-i-b  means 
that  a  is  to  be  divided  by  b.  This  divi- 
sion is  more  simply  expressed  by  making 
the  former  quantity  the  numerator,  and 
the  latter  the  denominator,  of  a  fraction, 
as  |",  which  expresses  the  quotient  of  a 
and  b. 

DIVISION,  FALLACY  OF.  A  fallacy 
in  Logic,  occasioned  by  using  the  middle 
term  in  the  major  premiss  collectively, 
and  in  the  minor  distributively,  the  term 
which  is  first  taken  collectively  being 
afterwards  divided. 

DIVISION,  LOGICAL.  A  metapho- 
rical expression  to  signify  "the  distinct 
(i.  e.  separate)  enumeration  of  several 
things  signified  by  one  common  name." 
It  is  analogous  to  the  real  division  of  a 
whole  into  its  parts,  and  is  directly  oppo- 
site to  generalization,  which  is  performed 
by  means  of  abstraction. 

DOBEREINER'S  LAMP.  A  method 
of  producing  an  instantaneous  light,  by 
throwing  a  jet  of  hydrogen  gas  upon 
recently-prepared  spongy  platinum ;  the 
metal  instantly  becomes  red  hot,  and 
then  sets  fire  to  the  gas.  The  discovery 
was  made  by  Dobereiner  of  Jena,  in  1824. 

DODE'CAGON  (dwde/ta,  twelve,  yovia, 
an  angle).  A  regular  polygon  of  twelve 
equal  sides.  The  area  of  such  a  figure 
is,  in  general,  equal  to  the  square  of  its 
side  multiplied  by  the  constant  number 
11196. 

DODECAGY'NIA  (dJ>6ena,  twelve, 
7U1/J7,  a  woman).  The  designation  of 
those  orders  of  plants  in  the  Linnaean 
system,  which  are  characterized  by  the 
presence  of  twelve  styles. 

DODECAHE'DRON  (dwSexa,  twelve, 
edpa,  a  seat).  A  geometrical  solid,  con- 
tained by  twelve  equal  pentagons,  which 
are  equilateral  and  equiangular. 

DODECA'NDRIA  (dcofexa,  twelve, 
uvijp,  a  man).  The  eleventh  class  of 
plants  in  the  system  of  Linnaeus,  charac- 
terized by  the  presence  of  twelve  stamens. 

DOG-DAYS.  The  period  of  the  year 
comprising  forty  days,  twenty  before  and 
twenty  after  the  heliacal  rising  of  the 
dog-star.  This  period,  being  the  hottest 
of  the  year,  was  considered  by  the  Greeks 
as  the  season  of  fevers,  plagues,  and 
death.     See  Canicular  Period. 

DOKIMA'STIC    ART    {ioiuntifa,    to 

prove  by  trial).     The    art    of  assaying 

minerals  and  ores,  in  order  to  determine 

the  quantity  of  metal  which  they  contain. 

112 


DOLA'BRIFORM  (dolabra,  an  axe, 
forma,  likeness).  Axe-shaped;  a  term 
applied  to  the  succulent  leaves  of  a 
species  of  Mesembryanthemum,  which 
are  thick  at  one  border  and  thin  at  the 
other. 

DO'LERITE.  One  of  the  varieties  of 
the  Trap  rocks,  composed  of  augite  and 
felspar. 

DO'LOMITE.  A  crystalline  lime- 
stone, containing  magnesia,  and  named 
after  the  French  geologist  Dolomieu. 
The  compact  or  brown  kind  is  commonly 
called  Magnesian  Limestone. 

DOMI'NICAL  LETTER.  One  of  the 
first  seven  letters  of  the  alphabet,  em- 
ployed in  the  calendar  to  denote  the 
Sundays,  or  days  of  the  Lord  (i.e.  Domini), 
throughout  the  year.  If  the  year  con- 
sisted of  exactly  52  weeks,  the  dominical 
letter  would  always  be  the  same ;  but,  as 
there  is  an  excess  of  l£  day,  the  Sunday 
letter  falls  back  one  letter  each  year,  ex- 
cept in  leap-year,  when  it  falls  back  two 
letters.  As  every  fourth  year  is  bissextile, 
and  as  the  number  of  letters  employed  is 
seven,  the  same  order  of  dominical  letters 
will  return  only  in  four  times  seven,  or 
twenty-eight  years,  whereas,  without  that 
intervention,  it  would  return  in  seven. 

DO'MITE.  A  white  mineral  found  in 
the  Puy  de  Dome  in  Auvergne. 

DO'RSAL  (dorsum,  the  back).  Any 
thing  placed  on  the  back.  In  Malaco- 
logy, the  term  is  applicable  to  the  valves 
of  bivalves,  in  which  it  serves  to  distin- 
guish that  part  of  their  circumference  on 
which  the  bosses  are  placed,  from  that 
which  is  nearest  the  belly,  when  the  ani- 
mal is  crawling.  The  upper  part  of  a 
spiral  shell,  when  the  mouth  is  down- 
ward, may  be  termed  its  back,  or  dorsal 
surface.  The  term  dorsad  signifies  to- 
wards the  back. 

DORSIBRA'NCHIA'TA  (dorsum,  the 
back,  branchia,  gills).  An  order  of  Anel- 
lida,  or  red-blooded  worms,  in  which  the 
branchial  tufts  are  attached  to  the  back. 
These  were  termed  by  Milne  Edwards 
errantes,  from  their  powers  of  locomo- 
tion. In  popular  language  they  are 
termed  sea-centipedes,  sea-mice,  or  ne- 
reids. 

DOUBLE  STARS.  A  term  applied 
to  some  fixed  stars  which,  though  appa- 
rently single  to  the  naked  eye,  are  found, 
by  means  of  the  telescope,  to  consist  of 
two  or  more  stars  exceedingly  near  to 
each  other. 

DOUBLER.  An  instrument  employed 
in  electrical  experiments,  and    so   con- 


DUC 


DUR 


trived  that,  by  executing  certain  move- 
ments, very  small  quantities  of  electricity 
communicated  to  a  part  of  the  apparatus 
may  be  continually  doubled,  until  it  be- 
comes perceptible  by  an  electroscope. 

DRACO.  The  Dragon;  a  northern 
constellation,  consisting  of  eighty  stars, 
the  principal  of  which  is  Rastaber. 

DRAUGHT  OF  WATER.  The 
depth  to  which  the  lowest  point  of  a  ship 
sinks  in  water ;  in  ships  of  the  largest 
size  the  draught  is  nearly  thirty  feet. 

DRIFT.  A  term  used  in  Navigation 
to  express  the  angle  which  the  line  of  a 
ship's  motion  makes  with  the  nearest 
meridian,  when  she  drives  with  her  side 
to  the  wind,  and  is  not  governed  by  the 
power  of  the  helm  ;  and  also  the  distance 
which  the  ship  drives  on  that  line  in  a 
storm. 

The  drift  of  a  current  is  its  velocity; 
the  direction  of  a  current  is  called  its  set. 

DROP.  The  smallest  perceptible  por- 
tion of  a  liquid.  It  is  of  a  globular  form, 
and  thus  illustrates  the  theory  that  the 
molecular  forces  of  all  bodies  are  equally 
exerted  around  the  centre  of  their 
masses. 

DROSO'METER  (3p6<rop,  dew,  fierpov, 
a  measure).  An  instrument  for  mea- 
suring the  quantity  of  dew  deposited 
upon  the  surface  of  a  body. 

DRUPE  {drupes,  unripe  olives).  In 
Botany,  a  pulpy  fruit,  without  a  valve  or 
outward  opening,  containing  a  bony  nut, 
as  the  cherry. 

DRY  PILE.  The  name  of  a  galvanic 
apparatus,  constructed  with  pairs  of 
metallic  plates,  separated  by  layers  of 
farinaceous  paste  mixed  with  common 
salt.  The  name  is  inappropriate,  as  the 
apparatus  evidently  owed  its  efficacy  to 
the  moisture  of  the  paste. 

DRY  ROT.  A  species  of  decay  to 
which  wood  is  subject.  The  wood  loses 
all  its  cohesion,  and  becomes  friable,  and 
fungi  generally  appear  upon  it ;  but  the 
first  destructive  change  is  probably  of  a 
chemical  kind,  allied  to  the  action  of  fer- 
mentation. 

DU'ALISM  (duo,  two).  A  system  of 
philosophy  which  refers  all  existence  to 
two  ultimate  principles. 

DU'BHE.  A  star  of  the  first  magni- 
tude in  the  northern  constellation  Ursa 
Maj  r. 

DUCT,  IN  PLANTS.  A  membranous 
tube  with  conical  or  rounded  extremities, 
and  its  sides  marked  with  transverse 
lines,  rings,  or  bars;  unlike  the  spiral 
vessel,  it  is  incapable  of  unrolling  with- 
113 


out  breaking.  The  varieties  are  the 
closed,  the  annular,  the  reticulated,  and 
the  scalariform. 

DUCTI'LITY  (duco,  to  draw).  That 
property  of  bodies  by  which  they  admit 
of  being  drawn  out  into  wire.  Platinum 
has  been  drawn  into  threads  not  much 
larger  than  those  of  the  spider's  web, 
and  gold  wire  has  been  found  so  thin, 
that  550  feet  of  it  weighed  only  one 
grain. 

DU'CTUS  (duco,  to  lead).  A  duct  or 
tube  which  conveys  away  the  secretion  of 
a  gland. 

DU'MASINE.  An  empyreumatic  oil, 
obtained  by  rectifying  acetone  derived 
from  the  acetates. 

DUMOSE  (dumus,  a  bush  or  bramble). 
The  character  of  a  shrub  which  is  low 
and  much  branched. 

DUNES  or  DOWNS.  Low  hills  of 
blown  sand  which  skirt  the  shores  of 
Holland,  England,  Spain,  and  other  coun- 
tries. 

DUODECIMALS  (duodecim,  twelve). 
An  operation  in  Arithmetic,  technically 
called  cross  multiplication  and  squaring 
of  dimensions.  Its  object  is  to  find  the 
contents  of  any  surface  or  solid  by  mul- 
tiplying together  its  linear  dimensions. 

DUPLICATE  RATIO.  The  compo- 
sition of  a  ratio  with  itself  once;  thus, 
the  ratio  of  a2  to  ft2  is  the  duplicate  of  the 
ratio  of  a  to  b.  If  there  be  three  quan- 
tities in  continued  proportion,  the  first 
is  to  the  third  in  the  duplicate  ratio  of 
the  first  to  the  second;  thus,  if  a,  b,  c 
be  continual  proportionals,  that  is,  if 
a  '.  b  '.  ;  b  '.  c,  then,  a  is  to  c  m  the  du- 
plicate ratio  of  a  to  b. 

DUPLICATION  OF  THE  CUBE.  A 
celebrated  problem,  proposed  by  the  ora- 
cle of  Delos,  viz.  "to  double  the  altar  of 
the  God ;"  this  was  tantamount  to  finding 
the  side  of  another  cube  of  twice  the  solid 
content.  This  problem,  requiring  the 
solution  of  a  cubic  equation,  was  inca- 
pable of  solution  by  pure  geometry,  and 
was,  therefore,  reduced  by  Hippocrates  of 
Chios  to  the  insertion  of  two  mean  pro- 
portionals between  two  given  straight 
lines. 

DU'PLO-  (duplum,  from  duo,  two, 
plica,  a  fold).  A  Latin  prefix,  signifying 
two-fold,  as  in  duplo-carburet ;  also,  that 
the  organs  of  any  body  to  which  the  term 
is  prefixed  are  twice  as  numerous  or  large 
as  those  of  some  other  body. 

DURA'MEN  (durus,  hard).  The  in- 
terior, more  deeply-coloured,  and  harder 
portion  of  the  trunk   and  branches  of 


EAR 


E  AS 


trees,  commonly  called  heartwood,  as  dis- 
tinguished from  the  exterior  portion, 
alburnum,  or  sapwood. 

DUTCH  GOLD.  An  alloy  of  copper 
and  zinc,  in  which  the  zinc  is  in  greater 
proportion  than  it  exists  in  brass.  It  is 
allied  to  tombac  and  pinchbeck. 

DUTCH  MINERAL.  Metallic  copper 
beaten  out  into  very  thin  leaves. 

DUTCH  PINK.  Chalk  or  whiting, 
dyed  yellow,  with  a  decoction  of  birch 
leaves,  French  berries,  and  alum. 

DYES.  Colouring  matters  derived  from 
vegetable  substances.     See  Lakes. 

DYKE  or  DIKE  (a  provincial  name 
for  wall).  A  term  applied  to  a  mass  of 
the  unstratified  or  igneous  rocks,  as 
granite,  trap,  and  lava,  when  it  appears 
as  if  injected  into  a  rent  in  the  stratified 
rocks,  cutting  across  the  strata.  A  mass 
of  this  kind  is  sometimes  seen  running 
along  the  ground,  and  projecting,  like  a 
wall,  owing  to  the  softer  strata  on  both 
sides  of  it  having  wasted  away.  A  dyke 
differs  from  a  vein  in  being  generally  of 
larger  dimensions,  and  having  its  sides 
parallel  for  a  considerable  distance ;  while 
a  vein  has  generally  many  ramifications, 
and  these  often  become  gradually  reduced 
to  slender  threads. 

Dyke  is  also  the  name  given  to  a  mound 


of  earth,  stones,  &c,  employed  as  a  bar- 
rier against  inundation  by  the  sea,  as  the 
dykes  of  Holland. 

DYNA'MICS  {dvvants,  force).  That 
branch  of  mechanics  which  relates  to 
the  action  of  forces  which  are  not  in 
equilibrio.  It,  therefore,  treats  of  bodies 
in  motion.    See  Statics. 

DYNAMIC  THEORY.  A  theory  for 
explaining  the  nature  of  matter,  or  the 
mode  of  its  formation,  invented  by  Kant. 
He  supposed  that  all  matter  existed  or 
was  originated  by  two  antagonist  and 
mutually  counteracting  principles,  which 
he  called  attraction  and  repulsion,  all 
the  predicates  of  which  he  referred  to 
motion.     See  Atomic  Theory. 

DYNAMO'METER  (*&«*<*  force, 
jueVpoi',  a  measure).  A  measurer  of 
power;  an  instrument  for  measuring, 
with  accuracy,  the  magnifying  powers  of 
microscopes  and  telescopes,  the  force  of 
machinery,  the  strength  of  animals,  &c. 

DYNA'STIDjE  (bwdartv,  a  master). 
A  family  of  beetles,  comprehending  the 
giants  of  the  Coleopterous  order,  remark- 
ably powerful  in  excavation. 

DYSO'DILE  (3u<rw3»jf,  fetid).  A  mi- 
neral found  near  Syracuse,  emitting,  on 
combustion,  an  insupportably  fetid  odour. 


E 


EAGLE  STONE.  Aetites  lapis.  A 
globular  clay  iron  stone,  supposed  to 
have  been  found  in  the  nest  of  the  eagle. 

EARTH.  Terra.  A  planet  of  the 
solar  system,  the  orbit  of  which  lies  be- 
tween Venus  and  Mars.  It  revolves 
round  the  sun  in  365  days,  5  hours,  and 
48  minutes,  at  the  distance  of  95  millions 
of  miles.  Its  diameter  is  7912  miles. 
Its  rotation  upon  its  axis  furnishes  a 
uniform  measure  of  time,  called  the 
sidereal  day. 

EARTH  (in  Chemistry).  A  solid, 
opaque,  friable  substance,  without  lustre, 
and  incombustible;  it  is  thus  distin- 
guished from  metals  on  the  one  hand, 
and  from  carbon  and  other  combustible 
substances  on  the  other.  In  chemical 
language,  the  earths  are  termed  metallic 
oxides,  and  formerly,  earths  of  the  metals. 
Four  of  these,  viz.  baryta,  strontia, 
lime,  and  magnesia,  are  termed,  from 
their  properties,  alkaline  earths. 
114 


EARTH  OF  ALUM.  A  preparation 
used  for  paints,  and  procured  by  preci- 
pitating the  earth  from  alum  dissolved 
in  water,  by  adding  ammonia  or  potass. 

EARTH  OF  BONE.  A  phosphate 
of  lime,  sometimes  called  bone  phos- 
phate, existing  in  bones  after  calcina- 
tion. 

EARTH-FALL.  A  natural  pheno- 
menon which  occurs  when  portions  of  the 
earth's  surface  are  elevated,  then  cleft 
asunder  and  depressed,  the  space  once 
occupied  by  solid  earth  becoming  covered 
with  water. 

EARTHQUAKE.  A  sudden  motion 
of  the  solid  surface  of  the  globe,  probably 
occasioned  by  the  same  causes  as  those 
which  produce  volcanic  eruptions. 

EAST.  That  point  of  the  compass 
which  is  in  a  direction  at  right  angles  to 
that  of  the  north  and  south,  and  towards 
the  right  hand  of  the  spectator  when 
facing  the  north.    It  is  that  point  of  the 


ECH 


ECL 


horizon  in  which  the  sun  is  seen  to  rise 
at  the  time  of  the  equinoxes. 

EASTER.  This  holiday  is  directed  to 
be  celebrated  on  the  first  Sunday  after 
the  full  moon  which  happens  next  after 
the  21st  of  March ;  this,  being  the  four- 
teenth day  of  the  first  Jewish  month, 
corresponds  with  the  first  day  of  the  week 
after  the  Passover,  the  anniversary  of 
the  Resurrection  of  Christ.  The  time  at 
which  this  day  must  happen  varies  with 
the  year ;  but  the  limits  within  which  it 
must  fall  are  the  22nd  of  March  and  the 
25th  of  April,  inclusive,  making  a  period 
of  thirty-five  days. 

EBULLITION  (ebullitio,  a  bubbling 
up).  The  boiling  or  bubbling  of  liquids ; 
the  production  of  vapour  at  the  boiling 
point. 

EBURNI'NjE.  A  sub  family  of  the 
Turbinellidce,  or  Turnip-shells,  named 
from  the  typical  genus  eburna,  and  hav- 
ing the  base  of  the  shell  truncate  and 
notched,  the  pillar  smooth,  and  the  inner 
lip  considerably  thickened  and  spreading. 

ECCE'NTRIC  {sk,  out,  nevrpov,  the 
centre).  A  term  applied  to  circles  and 
spheres  which  have  not  the  same  centre, 
and  consequently  are  not  parallel;  in 
opposition  to  concentric,  which  denotes  a 
common  centre,  and  therefore  paral- 
lelism. 

Eccentricity.  The  distance  of  the 
centre  of  the  orbit  of  a  planet  from  the 
centre  of  the  sun ;  that  is,  the  distance 
between  the  centre  of  the  ellipsis  and  the 
focus. 

E'CDYSIS  (&c3u<m,  the  act  of  strip- 
ping).   Moulting  of  the  skin. 

ECHTNATE  (ex*™?,  the  sea-hedge- 
hog). Bristly ;  covered  with  stiff  hairs 
or  prickles,  like  an  echinus ;  a  term  ap- 
plied to  bristly  fruits,  as  that  of  the  sweet 
chestnut,  &c. 

ECHI'NID-ffi  (exTvoc,  the  sea-hedge- 
hog). A  family  of  radiated  animais. 
comprehending  those  marine  animals 
commonly  known  by  the  name  of  sea- 
eggs  or  sea-urchins,  and  constituting, 
according  to  De  Blainville,  the  second 
order  of  the  class  Echinodermata.  By 
the  term  echini,  geologists  denote  the 
calcareous  petrifactions  of  the  echinus, 
which  occur  through  all  the  formations, 
from  the  epoch  of  the  transition  series  to 
the  present  time. 

ECHI'NODE'RMATA  (*xZ*ot,  the  sea- 
hedgehog,  bepua,  skin).  A  class  of  the 
Radiata,  comprising  aquatic  invertebrate 
animals,  which  have  the  surface  of  their 
skin  generally  covered  with  calcareous 
115 


spines,  as  the  common  sea-urchin  and 
the  star-fish.  The  following  orders  have 
been  founded  on  differences  of  their 
general  form : — 

1.  Crino'ida,  or  those  species,  chiefly 
fossil,  which  are  fixed  by  a  jointed  pe- 
duncle, and  have  long  ramified  articu- 
lated tentacula  extending  from  around 
the  abdominal  cavity,  as  in  encrinus  and 
pentacrinus. 

2.  Aster ida  or  Stellerida,  comprising 
the  articulated,  free,  flexible,  stellated 
species,  which  are  destitute  of  peduncle, 
and  with  a  short  axis,  as  in  asteria. 

3.  Echinida,  in  which  the  body  is  in- 
flexible and  covered  with  a  solid  articu- 
lated shell,  the  exterior  surface  being 
covered  with  moveable  calcareous  spines, 
as  in  echinus. 

4.  Holothurida,  in  which  the  axis  of 
the  body  is  placed  horizontally,  and  there 
is  a  soft,  coriaceous  skin,  seldom  pro- 
tected with  spines,  as  in  holothuria. — 
Grant. 

E'CHO  (hxu>  a  sound ;  especially,  a 
returned  sound).  A  wave  of  sound, 
which,  falling  perpendicularly  on  a  re- 
flecting surface,  returns  in  the  same 
direction,  and  arrives  at  the  spot  from 
which  it  originated. 

ECLIPSE  (ftcXei^M,  a  defect).  A 
lunar  eclipse  is  caused  by  the  projection 
of  a  shadow  upon  the  (full)  moon,  in 
consequence  of  the  interception  of  the 
sun's  rays  by  the  earth.  A  solar  eclipse 
is  occasioned  by  the  interception  of  a 
part  or  of  the  whole  of  the  sun's  rays,  by 
the  (new)  moon.  The  eclipse  is  partial, 
when  the  moon  hides  only  a  part  of  the 
sun's  disk ;  total,  when  she  covers  the 
whole  of  it;  annular,  when  the  sun, 
masked  by  the  moon,  projects  all  round 
in  the  form  of  a  luminous  ring ;  central, 
when  the  spectator's  place  is  in  the  pro- 
longation of  the  line  joining  the  centres 
of  the  sun  and  the  moon. 

ECLI'PTIC  (€K\et4ns,  an  eclipse).  The 
orbit  described  apparently  by  the  sun 
round  the  earth,  and  in  reality  by  the 
earth  round  the  sun.  It  is  named  from 
the  circumstance  that  all  eclipses  can 
happen  only  when  the  moon  is  in  the 
same  plane,  or  very  near  it.  The  lowest 
and  highest  points  of  the  ecliptic  are  the 
winter  and  summer  solstices  respectively. 
See  Solstice. 

1.  Ecliptic,  Obliquity  of.  The  inclina- 
tion of  the  ecliptic  to  the  equator  of  the 
earth,  amounting  to  an  angle  of  23°  28'. 
This  inclination  gives  rise  to  the  pheno- 
mena of  the  seasons. 


EPF 


EL  A 


2.  Ecliptic,  Plane  of.  A  plane  sup- 
posed to  pass  through  the  ecliptic,  and  to 
he  indefinitely  extended.  In  other  words, 
it  is  the  plane  which  contains  the  earth's 
orbit. 

3.  Ecliptic  Digit.  The  twelfth  part  of 
the  diameter  of  the  sun  or  moon  ;  a  term 
employed  for  defining  the  magnitude  of 
an  eclipse.  Thus,  an  eclipse  is  said  to  be 
of  ten  digits,  if  ten  parts  of  the  twelve 
constituting  the  diameter  are  concealed. 

4.  Ecliptic  Limits.  The  greatest  dis- 
tances at  which  the  moon  can  be  from 
her  nodes,  in  order  that  an  eclipse  of  the 
sun  or  moon  may  take  place. 

E'DDY  (Sax.  ed,  water,  ea,  backwards). 
A  circular  motion  of  the  water,  occurring 
in  rivers  when  the  proper  current  meets 
a  counter  current ;  and  in  seas,  where 
two  currents  run  in  parallel,  but  different, 
directions,  as  between  the  equatorial  and 
the  North  African  current.  See  Whirl- 
pool. 

EDENTATA  (edentulus,  toothless). 
An  order  of  the  Mammalia,  agreeing  in 
the  unimportant  character  of  the  absence 
of  incisive  teeth.  The  order  may  be 
distinguished  into  the  edentata  proper, 
containing  the  ant-eaters,  armadillos,  &c, 
all  of  which  are  insectivorous ;  and  the 
tardigrada,  or  sloths,  characterized  by 
the  slowness  of  their  motion. 

The  term  Edentata  has  also  been  ap- 
plied to  a  group  of  Crustaceous  animals, 
in  which  the  mouth  is  prolonged  in  the 
shape  of  a  sucker.    See  Maxillosa. 

E'DINGTONITE.  A  crystalline  mine- 
ral, found  implanted  upon  crystallized 
Thomsonite,  in  the  Kilpatrick  hills,  near 
Glasgow,  accompanied  by  calcareous  spar 
and  harmotone. 

EDRI'OPHTH A'LMA (Zdpalot,  sessile, 
6<p$a\/jLos,  the  eye).  A  group  of  the 
malacostracous  Crustacea,  which  have 
immoveable  sessile  eyes.  It  comprises 
the  orders  Amphipoda,  Laemodipoda,  and 
Isopoda.     See  Podophthalma. 

EDULCORA'TION  (dulcis,  sweet). 
The  process  of  freeing  a  difficultly  soluble 
substance  from  one  that  is  easily  soluble 
by  means  of  distilled  water.  It  differs 
little  from  lixiviation,  except  that  the 
former  term  respects  the  insoluble  re- 
sidue, the  latter  the  soluble  portion. 

EDULCORATOR.  Dropping  Bottle. 
An  instrument  for  supplying  small  quan- 
tities of  water  to  test  tubes,  watch-glasses, 
&c,  by  causing  water  to  drop  from  a 
phial,  properly  prepared,  by  expansion  of 
the  liquid  by  the  warmth  of  the  hand. 

EFFERVE'SCENCE  {effervesco,  to 
116 


grow  hot).  The  commotion  produced  in 
liquids  by  the  rapid  escape  of  gas,  in  the 
form  of  bubbles,  as  on  pouring  acid  on 
chalk. 

EFFLORE'SCENCE  (effloresco,  to  blow 
as  a  flower).  The  pulverescence  of  crys- 
tals, by  the  removal  of  their  moisture,  on 
exposure  to  the  air.     See  Deliquescence. 

E'GERAN.  A  sub-species  of  pyramidal 
garnet,  occurring  in  a  bed  of  felspar  and 
hornblende,  at  Haslan,  near  Eger  in  Bo- 
hemia. 

EIGHTH  (in  Music).  The  octave  or 
eighth  note  of  the  diatonic  scale.  It  is  a 
perfect  concord,  and  harmonizes  with  the 
fifth  and  the  third.  It  may  form  a  part 
of  any  chord. 

EI'SENRAHM.  A  term  applied  to 
a  red  and  a  brown  ore— the  scaly  iron 
ore,  and  the  scaly  magnetic  ore. 

ELA'IN  {e\aiov,  oil).  The  oily  prin- 
ciple of  solid  fats,  so  named  by  its  dis- 
coverer, Chevreul:  this  and  stearine 
constitute  the  fixed  oils.  Elaic  or  oleic 
acid  is  obtained  from  elain  by  saponi- 
fication with  a  strong  solution  of  pot- 
ash. 

ELA'OLITE  (ZXaiov,  oil,  A/0or,  a 
stone).  A  sub-species  of  pyramidal  fel- 
spar, of  a  blue  and  of  a  red  colour.  The 
former  is  opalescent,  and  is  termed  fett- 
stein  by  Werner,  from  its  resinous  nature. 

ELAIOMETER  ($\aiov,  oil,  perpov,  a 
measure).  An  instrument  for  detecting 
the  adulteration  of  olive  oil. 

ELAO'PTEN  (e'Xcuov,  oil).  The  liquid 
portion  of  a  volatile  oil.  The  concrete 
portion  is  called  stearopten. 

ELA'STIC  CURVE.  The  figure  as- 
sumed by  an  elastic  plate,  of  which  one 
end  is  fixed  horizontally,  while  the  other 
end  is  loaded  with  a  weight  which,  by  its 
gravity,  produces  the  curve. 

ELASTICITY  {kXavw,  to  push  or 
drive  back).  The  property  or  power  by 
which  a  solid  or  fluid  body,  when  com- 
pressed or  forcibly  expanded,  endeavours 
to  reassume  its  former  bulk. 

E'LATER  (eXa-r^p,  a  driver).  A  spiral 
fibre,  enclosed  in  a  membranous  case, 
found  in  great  numbers  mixed  with  the 
sporules,  in  the  thecae  of  some  crypto- 
gamic  plants.  When  fully  ripe,  the 
membranous  case  usually  disappears,  the 
spiral  fibres,  which  are  powerfully  hygro- 
metric,  uncurl,  and  the  sporules  are  dis- 
persed. 

ELATE'RIDjE.  A  family  of  Coleo- 
pterous insects,  belonging  to  the  section 
Sternoxi,  and  named  from  the  genus 
Elater,  a  species  of  which  (noctilucus) 


ELE 


ELE 


is  known  in  America  by  the  name  of  fire- 
fly. 

ELATE'RIUM  (e\ai->/p<or,  driving 
away).  A  term  applied  by  Richard  to 
the  tricoccous  capsule  of  Euphorbia,  in 
which  the  cells  burst  from  the  axis  with 
elasticity  into  two  valves.     See  Regma. 

ELEA'TIC  PHILOSOPHY.  A  sys- 
tem of  philosophy  introduced  by  Xeno- 
phanes  of  Elea,  or  Velia  of  the  Romans. 
Its  object  was  to  deny  the  validity  of  the 
testimony  of  sense  and  experience,  and 
to  ascribe  to  reason  exclusively  the  merit 
of  arriving  at  the  truth,  independently  of 
any  attempt  to  reconcile  appearance  and 
reality. 

ELECTRICITY  {r,XeKTpov,  amber). 
The  science  which  investigates  the  attrac- 
tions and  repulsions,  the  emission  of 
light  and  explosions,  which  are  produced, 
not  only  by  the  friction  of  vitreous,  resin- 
ous, and  metallic  surfaces,  but  by  the 
heating,  cooling,  evaporation,  and  mu- 
tual contact  of  a  vast  number  of  bodies. 

2.  Electricity,  vitreous  and  resinous. 
1.  Vitreous  electricity  comprises  the 
phenomena  exhibited  on  rubbing  surfaces 
of  glass.  This  is  also  called  plus  or  posi- 
tive electricity,  and  it  denotes  that  the 
substance  is  overcharged.  2.  Resinous 
electricity  relates  to  the  phenomena  dis- 
played on  rubbing  amber  or  resinous  sub- 
stances. This  is  also  called  minus  or 
negative  electricity,  and  it  denotes  that 
the  substance  is  undercharged. 

2.  Electrics  and  non-electrics.  The 
former  are  bodies  capable  of  electric  ex- 
citement ;  the  latter  are  bodies  totally 
incapable  of  it.  These  terms  were  for- 
merly supposed  to  be  respectively  syno- 
nymous with  non-conductors  and  con- 
ductors ;  but  the  distinction  is  quite  inac- 
curate, since  a  conductor  may  be  also  an 
electric,  if  excited  in  an  insulated  state. 

3.  Electric  circuit.  The  communica- 
tion of  electricity  from  one  body  to  an- 
other is  effected  by  means  of  metallic 
wires.  It  is  said  to  move  in  a  current, 
from  an  overcharged  to  an  undercharged 
body ;  this  current  is  termed  the  electric 
circuit.  If  the  communication  be  ar- 
rested by  bad  conductors,  the  circuit  is 
said  to  be  broken ;  it  is  at  this  point  of 
the  circuit  that  bodies  are  placed,  through 
which  the    electrical  current    is    to    be 


4.  Electrical  machine.  An  apparatus 
for  developing  a  large  quantity  of  elec- 
tricity of  high  tension.  It  consists  of 
1,  a  non-conductor,  usually  of  glass,  which 
is  positively  excited  by  friction;  2,  a 
117 


rubber,  or  soft,  elastic  substance,  of  low 
conducting  power,  which  is  negatively 
excited;  and  3,  two  conductors,  which 
are  hollow,  insulated,  metallic  cylinders, 
the  one  for  receiving  the  positive  elec- 
tricity of  the  glass,  the  other,  the  nega- 
tive electricity  of  the  rubber ;  the  former 
is  called  the  positive,  the  latter  the  nega- 
tive conductor. 

5.  Electric  current.  The  discharge  of 
electricity  by  convection,  or  the  transfer 
of  the  two  electrical  forces  in  opposite 
directions,  defined  by  Faraday  as  "an  axis 
of  power  having  contrary  forces,  exactly 
equal  in  amount,  in  contrary  directions." 

6.  Electrical  columii.  A  species  of 
electrical  pile,  invented  by  De  Luc,  com- 
posed of  thin  plates  of  different  metals  in 
the  usual  order,  with  discs  of  writing 
paper  interposed  between  them. 

ELECTRICITY,  ANIMAL.  Galvan- 
ism. A  power  possessed  by,  and  evolved 
from,  certain  living  animals,  by  means  of 
which  several  of  the  phenomena,  exhi- 
bited by  common  and  by  voltaic  elec- 
tricity, are  produced.  Volta  proved,  that 
the  phenomena  proceeded  from  the  con- 
tact of  two  dissimilar  metals,  copper  and 
iron,  producing  such  a  disturbance  of  the 
electric  equilibrium,  as  was  sufficient  to 
affect  the  most  delicate  of  all  electro- 
scopes, the  irritability  of  a  newly-killed 
frog,  though  it  was  insensible  to  every 
electroscope  of  human  construction. 

ELECTRO-CHEMISTRY.  A  system 
of  chemistry  based  on  the  assumption  that 
the  attractive  force  of  opposite  electricities 
is  the  fundamental  cause  of  all  chemical 
combination ;  every  compound  substance, 
therefore,  consists  of  one  positively  and 
one  negatively  electrified  element. 

ELE'CTRODE.  A  term  in  Electricity, 
synonymous  with  pole,  denoting  the  waij 
(6d6s)  by  which  the  electric  current 
enters  or  departs.  It  is,  therefore,  the 
boundary  of  the  decomposing  matter  in 
the  direction  of  the  electric  current,  the 
anode  being  the  point  at  which  the  elec- 
tricity enters,  or  the  point  immediately 
touching  the  positive  pole ;  the  kathode, 
the  point  at  which  the  electricity  departs, 
or  the  point  next  to  the  negative  pole. 

ELECTRO-DYNAMICS.  The  science 
which  investigates  the  phenomena  of 
electricity  in  motion  ;  and  this  comprises 
the  phenomena  of  electro-magnetism 
and  magneto-electricity. 

ELECTRO'LYSIS  (\va>,  to  decom- 
pose). The  process  of  resolving  a  com- 
pound body  into  its  elements,  or  proxi- 
mate principles,  by  the  voltaic  current. 


ELE 


ELE 


Substances  directly  decomposable  by 
electricity  are  termed  electrolytes.  The 
elements  of  an  electrolyzed  body  are 
called  ions— that  which  passes  to  the 
anode,  anion ;  that  to  the  kathode,  kation. 
Thus,  if  water  be  electrolyzed,  oxygen 
and  hydrogen  are  ions;  the  former  an 
anion,  the  latter  a  kation. 

ELECTRO-MAGNETISM.  The  sci- 
ence which  comprehends  all  the  pheno- 
mena in  which  electricity  develops  mag- 
netic influences. 

ELECTRO-METALLURGY.  The  art 
of  working  in  metals  by  galvanic  agency. 

ELECTRO'METER  (/xeTpov,  a  mea- 
sure). An  instrument  for  ascertaining 
the  intensity  of  electricity,  or  the  quan- 
tity and  quality  of  electricity  in  an  elec- 
trified body. 

ELECTROMOTIVE  FORCE.  A  term 
applied  by  Volta  to  the  development  of 
electricity  in  voltaic  combinations.  The 
bodies  by  whose  mutual  contact  it  is 
developed  are  called  electromotors. 

ELECTRO-NEGATIVES  and  POSI- 
TIVES. These  terms  denote  that,  during 
decomposition,  bodies  exhibit  a  different 
electric  condition  from  that  of  the  pole 
at  which  they  appear.  The  former  are 
those  bodies  which  appear  at  the  positive 
pole  of  the  battery ;  the  latter  are  those 
which  pass  to  the  negative  pole.  Oxygen 
is  the  most  electronegative,  potassium 
the  most  electro-positive,  of  all  known 
bodies. 

ELECTRO'PHORUS  (0<sPw,  to  carry). 
A  carrier  of  electricity :  an  instrument 
which  possesses  the  property  of  main- 
taining for  a  length  of  time,  by  its  in- 
ductive process,  the  electrical  tension 
which  has  been  excited  by  friction  in  a 
non-conductor. 

ELE'CTROPO'LAR.  A  term  applied 
to  conductors,  one  end  or  surface  of 
which  is  positive,  the  other  negative — a 
condition  which  they  commonly  exhibit 
when  under  the  influence  of  induction. 

ELE'CTROSCOPE  (o-kottpo),  to  ex- 
amine). An  instrument  for  indicating 
electrical  excitement,  and  the  electrical 
state  by  which  it  is  produced  ;  in  other 
words,  for  exhibiting  the  attractive  and 
repulsive  agencies  of  electricity. 

ELECTRO  -  THERMANCY.  The 
branch  of  science  which  investigates  the 
effects  produced  by  the  electric  current 
upon  the  temperature  of  good  conductors, 
when  it  passes  from  one  metal  into  an- 
other in  the  same  circuit.  These  effects 
are  the  converse  of  those  of  thermo-elec- 
tricity. I 
118 


ELECTRO-TINT.  An  application  of 
electrotype,  in  which  the  required  sub- 
ject is  painted  on  copper  with  a  thick 
varnish  or  paint ;  the  plate  is  then  pre- 
pared in  the  usual  way,  and  submitted  to 
the  voltaic  circuit ;  a  plate  is  thus  ob- 
tained from  which  prints  are  furnished. 

ELECTROTO'NIC  STATE.  The  pecu- 
liar latent  state  of  an  induced  conductor, 
during  the  continued  action  of  the  elec- 
tric current  upon  it,  resembling  that  of  a 
conductor  put  in  a  state  of  tension  by  in- 
duction. 

ELECTROTYPE.  The  science  by 
which  facsimile  medals  are  executed  in 
copper  by  means  of  electricity.  It  con- 
sists in  preparing  for  a  negative  plate 
models  or  moulds  of  objects  to  be  co- 
pied ;  and  in  so  arranging  the  battery,  or 
apparatus  which  generates  the  voltaic 
current,  as  to  release  the  metals  in  a 
compact  and  solid  form. 

ELECTRO  -  VITAL  CURRENTS. 
Neuro-vital  Currents.  The  name  of  two 
electric  currents,  supposed  to  exist  in 
animals, — the  one  external  and  cuta- 
neous, moving  from  the  extremities  to 
the  cerebro-spinal  axis  ;  the  other  inter- 
nal, going  from  the  cerebro-spinal  axis  to 
the  internal  organs  situated  beneath  the 
skin. 

ELE'CTRUM.  Argentiferous  gold ;  an 
ore  of  gold,  consisting  of  64  parts  gold, 
and  36  silver,  occurring  together  with 
massive  heavy  spar  in  Siberia. 

ELEMENT.  A  simple  substance ;  a 
substance  which  has  not  been  chemically 
resolved  into  different  substances,  as 
iron.  The  rust  of  iron,  on  the  other 
hand,  is  a  compound,  being  resolvable 
into  metallic  iron,  oxygen,  and  carbonic 
acid.  A  compound  may  consist  of  sub- 
stances which  are  susceptible  of  further 
decomposition :  these  are  called  proxi- 
mate elements.  If  the  decomposition  be 
repeated  without  obtaining  simple  sub- 
stances, the  constituents  then  found  are 
intermediate  elements ;  and  those  last 
arrived  at  are  known  as  ultimate  ele- 
ments. 

Example  .-—Saltpetre  is  a  compound. 
It  consists  of  two  compounds,  potash 
and  nitric  acid :  these  are  proximate  and 
intermediate  elements.  Each  of  these  is 
resolvable — the  former  into  potassium 
and  oxygen,  the  latter  into  nitrogen  and 
oxygen  :  these  are  ultimate  elements. 

E'LEMI.    A  resin  which  exudes  from 
incisions  made  in  the  bark  of  the  Amyris 
elemifera,  an  American  tree. 
ELE'NCHUS    {eXeyxos,  a  proof).    In 


ELL 


EMA 


Logic,  a  syllogism  by  which  the  adversary 
is  forced  to  contradict  himself.  The 
ignoratio  elenchi,  commonly  called  the 
fallacy  of  irrelevant  conclusion,  is  a 
sophism  which  consists  in  proving  some- 
thing irrelevant,  and  therefore,  though 
it  may  be  perfectly  true,  it  does  not  de- 
termine the  question.  The  latent  fallacy 
is  best  exposed  by  showing  that  both 
propositions  may  be  equally  true. 

ELEVATING  CAUSES.  A  term  ap- 
plied in  Geology  to  those  causes  which 
refer  to  the  operation  of  volcanoes,  earth- 
quakes, and  gradually  elevating  forces. 
As  degrading  causes  are  chiefly  owing  to 
water,  so  elevating  causes  are  chiefly 
owing  to  fire,  and  are,  therefore,  some- 
times comprehended  under  the  term 
igneous  agency. 

ELEVATION  {elevo,  to  lift  up).  In 
Astronomy,  the  altitude  or  angular 
height  of  a  celestial  body  above  the 
horizon.  The  elevation  of  the  pole  is  the 
arc  of  the  meridian  intercepted  between 
the  pole  and  the  horizon. 

ELIMINATION  (elimino,  to  put  out). 
The  algebraical  operation  of  reducing  a 
number  of  equations,  containing  certain 
letters,  to  a  smaller  number,  in  which 
one  or  more  of  the  letters  shall  not  occur. 
To  eliminate  a  quantity  is,  therefore,  to 
cause  that  quantity  to  disappear  from  an 
equation. 

ELIQUATION  (eliquo,  to  clarify).  The 
separation  of  a  more  fusible  from  a  less 
fusible  substance,  by  applying  a  degree 
of  heat  sufficient  to  fuse  the  former,  but 
not  the  latter. 

ELI'SION  (elisio,  a  cutting  off).  In 
Grammar,  the  cutting  off  a  vowel  at  the 
end  of  a  word,  for  the  sake  of  euphony 
or  of  metre. 

ELIXIR  (elikscir,  Arab.,  an  essence, 
or  pure  mass  without  any  dregs).  A 
term  formerly  applied  to  compound  tinc- 
tures, and,  by  the  alchemists,  to  various 
solutions  in  the  art  of  transmutation. 

ELLAGIC  ACID  (from  the  word galle, 
read  backward).  An  acid  which  is  ob- 
tained from  galls,  in  the  process  for 
making  gallic  acid. 

ELLIPSE  (<?XXe<i/^?,  a  defect).  A  sec- 
tion of  a  right  cone  by  a  plane  oblique  to 
its  base,  but  which  does  not  meet  it.  It 
is  named  frpm  its  plane  forming  with  the 
base  of  the  cone  a  less  angle  than  that  of 
the  parabola.  To  describe  it,  fix  a  cir- 
cular thread  by  two  points,  and,  keeping 
it  at  full  stretch  with  the  point  of  a  pen- 
cil, carry  the  pencil  all  round :  the  two 
fixed  points  are  the  foci  of  the  ellipse, 
119 


and  its  eccentricity  is  its  distance  from 
the  centre  to  the  foci. 

Ellipse,  axes  of.  By  generalizing  these 
directions,  we  learn  that  an  ellipse  is  a 
plane  figure  bounded  by  one  curved  line, 
of  such  a  nature  that  the  respective  sums 
of  the  distances  of  any  two  points  in  it 
from  the  two  foci,  are  equal.  The  line 
which  joins  the  foci,  and  terminates  both 
ways  in  the  circumference,  is  the  major 
axis;  the  line  drawn  through  the  centre 
at  right  angles  to  the  major  axis,  and 
terminating  both  ways  in  the  circum- 
ference, is  the  minor  axis  of  the  ellipse. 

ELLFPSOID  (e'XXetvW?,  an  ellipse, 
e'idoi,  likeness).  A  term  generally  ap- 
plied to  a  spheroid.  The  ellipsoid  of 
revolution  is  the  solid  generated  by  the 
revolution  of  an  ellipse  about  its  lesser 
axis. 

ELLI'PSOSTO'MATA.  A  family  of 
Gasteropods,  in  the  arrangement  of  De 
Blainville,  including  all  the  pectini- 
branchiate  gasteropods  of  Cuvier,  except 
the  genus  pleurocerus. 

ELLI'PTIC  COMPASSES.  An  in- 
strument for  describing  an  ellipse  by 
continued  motion. 

ELLIPTI'CITY.  A  term  employed 
in  describing  the  figure  of  the  earth,  to 
denote  the  deviation  of  the  earth's  form 
from  that  of  a  sphere.  It  means  the 
fraction  which  the  excess  of  the  major 
axis  over  the  minor  axis  of  an  ellipse  is 
of  the  minor  axis  itself. 

ELONGATION.  An  astronomical 
term  for  the  angular  distance  between 
two  celestial  bodies,  as  seen  from  the 
earth.  The  term  is  commonly  applied  to 
bodies  of  the  solar  system,  one  of  which 
is  generally  the  sun.  Hence,  we  speak 
of  the  distance  of  two  fixed  stars,  but  of 
the  elongation  of  Mercury  from  the  sun. 

ELUTRIATION  {elutrio,  to  cleanse). 
The  chemical  process  of  washing,  by 
which  the  lighter  earthy  parts  are  sepa- 
rated from  the  heavier  and  metallic. 

ELVAN  COURSES.  A  local  desig- 
nation of  the  large  beds  or  dykes  of  gra- 
nite which  frequently  occur  in  the  slaty 
rocks. 

ELYTRA  (e'Xm-pov,  a  sheath).  The 
wing  sheaths,  or  upper  crustaceous  mem- 
branes, which  form  the  superior  wings  of 
Coleopterous  insects.  They  cover  the 
body,  and  protect  the  true  membranous 
wings. 

EMA'RGINATE  (<?,  out  of,  margo,  the 
margin).  Having  a  notch,  as  if  a  portion 
had  been  cut  out  of  the  margin,  as  the 
base  of  most  predaceous  testacea,  not  pro- 


EME 


EN  A 


vided  with  a  canal ;  the  leaf  of  hox,  &c. 
The  term  is  opposed  to  immarginate. 

EMBERIZIN.E  (emberiza,  the  bunt- 
ing). Emberizine  birds,  or  Buntings ;  a 
family  of  the  Deglubitrices  of  Macgil- 
livray,  which  gradually  pass  into  the 
passeres,  or  sparrows.  They  have  a  strong, 
rapid,  rather  undulated  flight,  and  move 
on  the  ground  by  short  leaps. 

EMBOITEMENT  (the  situation  of 
one  box  within  another,  from  boite,  a 
box).  A  term  used  by  Bonnet  to  describe 
that  species  of  generation  by  which 
hundreds  and  thousands  of  individuals 
lie  one  within  the  other,  each  possessing 
a  complete  series  of  organized  parts.  See 
Evolution. 

EMBOLI'SMIC  {en(3o\iarn6s,  inter- 
calation). A  terra  synonymous  with 
intercalary,  generally  applied  to  the  ad- 
ditional months  required  to  fill  up  the 
lunar  cycle. 

E'MBRYO  {enftpvov,  from  ev,  in,  fovea, 
to  bud  forth).  Corculum.  In  Botany,  a 
fleshy  body  occupying  the  interior  of  the 
seed,  and  constituting  the  rudiment  of 
the  future  plant.  It  is'  distinguished 
into  three  parts,  the  radicle,  the  coty- 
ledons, and  the  plumule. 

1.  Embryo-buds.  A  term  applied  by 
Dutrochet  to  those  nodules  which  occur 
in  the  bark  of  the  beech,  and  some  other 
trees,  and  which  are  externally  indicated 
by  small  tumours  of  the  bark.  He  con- 
siders them  to  be  adventitious  buds 
arrested  in  their  development. 

2.  Embryo,  Fixed.  This  term  has 
been  applied  by  some  botanists  to  the 
leaf-bud.  The  function  of  the  two  or- 
gans is  analogous,  but  their  origin  and 
structure  are  entirely  different.  The  leaf- 
bud  consists  of  both  vascular  and  cellular 
tissue,  the  embryo  of  cellular  tissue  only  ; 
the  leaf-bud  is  produced  without  fertili- 
zation, which  is  essential  to  the  embryo ; 
lastly,  the  leaf-bud  perpetuates  the  indi- 
vidual, the  embryo  continues  the  species. 

EMBRYO'TEGA  (enfipvov,  embryo, 
T670?,  a  covering).  A  small  callosity  ob- 
served in  some  seeds,  at  a  short  distance 
from  the  hilum ;  it  gives  way,  like  a  lid 
or  covering,  at  the  time  of  germination, 
for  the  emission  of  the  radicle  of  the 
embryo. 

E'MERALD.  A  gem  found  in  Peru, 
of  a  green  colour,  rather  harder  than 
quartz,  and  always  in  crystals,  which  are 
translucent  and  generally  transparent. 
Prismatic  emerald  is  the  euclase  of  Haiiy ; 
rhomboidal  emerald  comprises  the  pre- 
cious emerald  and  beryl.  What  if?  called 
120 


Oriental  emerald  is  a.  green  sapphire.  The 
emerald  of  Brazil  is  a  tourmaline. 

EME'RSION.  An  astronomical  term, 
denoting  the  re-appearance  of  a  heavenly 
body  from  behind  another,  after  an  eclipse 
or  occultation. 

E'MERY.  A  granular  variety  of 
corundum,  found  in  Spain,  the  Greek 
islands,  &c,  and  named  from  Cape 
Emeri,  in  the  island  of  Naxos.  When 
triturated  and  attached  to  brown  paper, 
it  forms  emery  paper,  and  is  used  for 
polishing. 

EMISSION,  THEORY  OF.  Corpus- 
cular theory.  A  theory  propounded  by 
Newton  for  explaining  the  nature  of 
light.  According  to  this,  the  sun,  as  well 
as  all  luminous  bodies,  has  the  property 
of  emitting  exceedingly  minute  particles 
of  its  substance  in  right  lines  with 
prodigious  velocity.  See  Undulatory 
Theory. 

EMPI'RICAL  (k/jiTreiptKos,  expe- 
rienced). A  term  applied  to  an  act 
which  is  purely  experimental,  or  per- 
formed without  previous  experience  or 
principle  of  guidance.  It  is  remarkable 
that  the  term  empiricism,  which,  strictly 
speaking,  is  the  character  of  modern 
science,  should  have  fallen  into  disgrace, 
and  serve  only  to  designate  the  practice 
of  ignorant  pretenders  in  the  medical 
art. 

EMPYREU'MA  (fcffvptft*,  to  set  on 
fire).  The  peculiar  vapour  produced  by 
destructive  distillation.  Empyreumatic 
oils  are  obtained  by  distilling  organic 
substances  at  high  temperatures.  Harts- 
horn is  called  the  empyreumatic  alkali. 

E'MYDJE  (emys,  a  tortoise).  Fresh- 
water Turtles,  or  Mud-Tortoises ;  a 
family  of  Chelonian  reptiles,  intermediate 
in  form  between  the  turtles  and  the  land- 
tortoises.  They  are  distinguished  from 
the  marine  turtles  by  the  distinctness  of 
their  clawed  toes,  which  are,  however, 
webbed,  to  enable  them  to  swim,  and  to 
prevent  their  sinking  in  the  mud. 

E'MYDO-SAURIANS(|Mu?,  the  water- 
tortoise,  aavpa,  a  lizard).  An  order  of 
the  class  Reptilia,  including  the  tribe  of 
Crocodiles,  which  form  part  of  the  order 
Sauria  of  Cuvier. 

ENA'MEL.  A  peculiar  preparation 
of  glass,  used  in  painting  on  enamel,  in 
the  imitation  of  precious  stones,  &c. 
Common  glass,  fused  with  oxide  of  tin, 
is  converted  into  enamel. 

ENA'LIOSAU'RIA  (evdXios,  marine, 
aavpa,  a  lizard).  An  order  of  Reptiles, 
intermediate  between  the  Turtles   and 


END 


ENH 


Crocodiles,  and  comprising  the  fossil 
genera  Ichthyosaurus  and  Plesiosaurus, 
marine  animals  connected  with  the 
Chelonia  by  the  flattening  of  their  ex- 
tremities into  fin-like  paddles. 

ENCAU'STIC  PAINTING  {hyKava- 
Tt/coc,  belonging  to  burning  in).  A 
method  of  painting  employed  by  the 
ancients,  in  which  the  colours  were  ren- 
dered permanent  by  a  process  of  heating 
or  burning.  The  practice  is  briefly, 
but  not  sufficiently,  described  by  Pliny, 
in  his  "  Natural  History,"  xxx.  11. 

ENCE'PHALA  {ev,  in,  Ke<pa\tj,  the 
head).  Those  molluscous  animals  which 
have  a  distinct  head. 

ENCEPHALA'TA  {ky<e(pa\ov,  the 
brain).  A  term  applied  by  Dr.  Grant  to 
the  Vertebrata,  consisting  of  animals 
in  which  the  brain  is  enclosed  in  a  bony 
cavity. 

ENCHELIDE  MONAD.  An  animal- 
cule which  performs  the  usual  function 
of  the  green  parts  of  plants,  decomposing 
carbonic  acid  and  evolving  oxygen,  under 
the  influence  of  the  light  of  the  sun. 

ENCHO'RIAL  WRITING  {kyxuptos, 
belonging  to  a  country).  The  common 
mode  of  writing  among  the  Egyptians, 
resembling  the  Chinese  method,  and  also 
called  demotic  and  epistolographic.  It 
was  termed  enchorial,  because  its  cha- 
racters differed  from  those  employed  in 
Greece. 

ENCKE'S  COMET.  A  periodic  comet 
of  the  solar  system,  revolving  round  the 
sun  in  about  1200  days,  within  the  orbit 
of  Jupiter. 

E'NCRINITES  {kv,  in.  Kpivov,  a  lily). 
Stone-lilies.  Petrified  radiated  animals, 
included  by  Cuvier  among  his  pedicil- 
lated  echinoderms.  The  term  is  fre- 
quently applied  to  the  crinoidea  gene- 
rally, both  recent  and  fossil. 

ENDE'CAGON  {Zv&eica,  eleven,  ymwta, 
an  angle).  A  plane  geometrical  figure 
bounded  by  eleven  sides.  If  the  sides 
are  all  equal,  and  the  length  of  each  be 
supposed  =1,  the  area  of  the  figure  is 
9-36564. 

ENDO-  (hdov).  A  Greek  adverb, 
signifying  in,  within. 

1.  Endo-carp  Uapndt,  fruit).  The  in- 
nermost of  the  three  layers  which  collec- 
tively form  the  pericarp  of  fruits;  when 
it  is  of  a  bony  consistence,  it  is  also 
termed  putamen.  The  stone  of  the  drupe 
is  the  putamen  or  endocarp  ;  by  Richard, 
however,  it  is  termed  the  nux  or  nut. 

2.  Endo-gen  {yeivofxai,  to  be  produced). 
Inside-grower;  a  plant  which  increases 

121 


in  diameter  by  deposition  to  the  centre ; 
a  term  descriptive  of  the  structure  of  the 
axis  of  monocotyledonous  plants,  in 
which  the  newest-formed  fibres  are  al- 
ways developed  towards  the  centre  of  the 
stem. 

3.  Endo-phlosum  {<p\ot6s,  bark).  The 
liber,  or  the  innermost  layer  of  the  bark 
of  exogenous  plants,  composed  partly  of 
cellular,  partly  of  woody  tissue. 

4.  Endo-phyllous  {<pv\\ov,  a  leaf).  A 
term  applied  by  Dumortier  to  the  endo- 
rrhizous  embryo,  in  consequence  of  the 
young  leaves  of  monocotyledons  being 
evolved  from  a  coleophyllum,  or  leaf- 
sheath. 

5.  Endo-pleura  (irXevpa,  the  side).  The 
innermost  layer  of  the  testa,  or  integu- 
ment of  the  seed  of  plants,  named  by 
Willdenow  tunica  interna,  and  by  Mirbel, 
tegmen  and  hilofere. 

6.  Endo-ptile  (iniXov,  a  feather).  A 
term  applied  by  Lestiboudois  to  the  mo- 
nocotyledonous embryo,  in  consequence 
of  its  plumule  being  enclosed  within  the 
cotyledon. 

7.  Endo-rrhizous  (piga,  a  root).  A 
term  expressive  of  the  mode  of  germina- 
tion in  endogenous  plants,  in  which  the 
radicles  are  emitted  from  within  the  sub- 
stance of  the  radicular  extremity  of  the 
embryo,  and  are,  in  fact,  enclosed  within 
a  sheath  of  this  substance,  called  the 
coleoptile,  coleophyllum,  or  leaf-sheath. 

8.  End-osmose  (wo/sor,  impulsion).  The 
property  by  which  a  rarer  fluid  passes 
through  membranous  substances  into  a 
cavity  or  space  containing  a  denser  fluid. 
The  endosmometer  is  an  instrument  con- 
trived by  Dutrochet  for  measuring  the 
force  of  this  action. 

9.  Endo-siphonites  (<ri<p<av,  a  tube).  A 
genus  of  extinct  Cephalopods,  with  cham- 
bered convolute  discoidal  shells,  having 
the  siphon  placed  at  the  inner  side  of  the 
convolutions,  as  in  spirula.  They  occur 
in  the  slate  rocks  of  the  Cambrian  sys- 
tem. 

10.  Endosperm  {critepixa,  seed).  That 
which  is  within  the  seed  :  a  term  applied 
by  Richard  to  the  albumen,  or  body  en- 
closing the  embryo.  By  Jussieu,  it  was 
called  perisperm. 

11.  Endo-stome  (o-Toyua,  a  mouth).  The 
foramen  or  orifice  of  the  inner  integu- 
ment, or  secundine,  of  the  ovule,  in 
plants. 

12.  Endo-thecium  {Own*  a  case).  A 
term  applied  by  Purkinje  to  the  fibro- 
cellular  lining  of  the  anther,  in  plants. 

ENHARMO'NIC    SCALE.      A  scale 
G 


ENT 


EPA 


in  Music,  which  proceeds  by  quarter 
tones.  Thus  a  distinction  is  made  be- 
tween C  sharp  and  D  flat,  the  former 
being  }j|ths,  the  latter  $jths  of  the  string 
sounding  C.  The  transition  from  the 
one  to  the  other  of  these  intervals  is 
called  an  enharmonic  change,  and  a 
change  of  key  so  effected  is  termed  an 
enharmonic  modulation.  In  the  modern 
scale  these  intervals  are  practically  dis- 
regarded. 

E'NNEAGON  (ewea,  nine,  fwvia,  an 
angle).  A  plane  geometrical  figure 
bounded  by  nine  sides.  Assuming  the 
sides  to  be  equal,  and  representing  a 
side  by  1,  the  area  of  an  enneagon  is 
6-18182. 

ENNEA'NDRIA  (4Wa,  nine,  avtjp, 
man).  The  ninth  class  of  plants  in  the 
system  of  Linnaeus,  characterized  by  the 
presence  of  nine  stamens. 

ENS.  The  present  participle  of  the 
verb  sum,  employed  as  a  substantive  in 
philosophical  language  for  any  being  or 
existence.  In  Chemistry,  it  denotes  a 
substance  supposed  to  contain  all  the 
qualities  or  virtues  of  the  ingredients 
from  which  it  is  drawn,  in  a  small  com- 
pass :  thus  we  have  ens  Martis,  ammo- 
niated  iron ;  ens  Veneris,  muriate  of 
ammonia  and  copper;  ens  primum,  an 
alchemical  tincture  for  the  transmutation 
of  the  metals. 

E'NSIFORM  (ensis,  a  sword,  forma, 
likeness).  Gladiate.  Sword-shaped ; 
lorate  ;  straight,  flat,  and  pointed,  as  the 
leaf  of  iris. 

ENTHELMI'NTHA  (irtfe,  within, 
eXfxivi,  a  worm).  Intestinal  worms;  a 
term  synonymous  with  entozoa. 

E'NTHYMEME  (l^n/xa,  a  thought). 
An  argument,  called  by  Aristotle  the 
rhetorical  syllogism,  i.  e.  a  syllogism 
drawn  from  probable  premises,  and 
which,  therefore,  does  not  pretend  to  be 
demonstrative.  In  Logic,  however,  the 
term  denotes  an  abridged  form  of  argu- 
ment or  syllogism,  in  which  one  premiss 
is  expressed,  and  the  other  understood, 
whether  major  or  minor,  as  "  Caesar 
was  a  tyrant ;  therefore  he  deserved 
death." 

ENTIRE.  A  term  applied,  in  Botany, 
to  leaves  which  have  no  marginal  divi- 
sion, or  toothings  of  any  kind,  as  the 
leaves  of  galium.  Sometimes  it  denotes 
not  pinnatifid ;  and  also,  nearly  destitute 
of  marginal  division. 

E'NTOMOLINE  (eVro^ov,  an  insect). 
A  peculiar  chemical  principle,  found  in 
large  quantities  in  the  wings  and  elytra 
122 


of  coleopterous  insects,  and  termed  chi- 
tine  by  M.  Odier. 

ENTOMO'LOGY  (evTo^ov,  an  insect, 
\6fos,  an  account).  That  branch  of 
Zoology  which  treats  of  insects.  The 
Greek  word  evro/jia,  as  well  a3  the  Latin 
term  insecta,  relates  to  the  division  of 
the  body  of  these  animals  into  numerous 
segments. 

ENTOMO'PHAGOUS  (eVroMa,  in- 
sects, (ptiyo,  to  devour).  Insect-eating; 
a  term  applied,  in  Zoology,  to  those  ani- 
mals which  subsist  on  insects. 

ENTOMOSTO'MATA  (foropo*  an 
insect,  o-To/ia,  a  mouth).  The  name 
given  by  De  Blainville  to  a  family  of 
conchiferous  mollusca,  in  which  the 
mouth  is  armed  with  a  proboscis.  They 
constitute  the  second  family  of  his  first 
order  Siphonobranchiata,  and  are  nearly 
identical  with  the  genus  buccinum  of 
Linnaeus. 

ENTOMO'STRACA  (li/xo/xa,  insects, 
ocrTpaKov,  a  shell).  Shell  insects  ;  a  sec- 
tion of  the  Crustacea,  many  of  which  are 
enclosed  in  an  integument,  like  a  bivalve 
shell.  They  are  distinguished  into  the 
Entomostraca  proper,  and  the  Xipho- 
sura.  The  orders  are  Copepoda  and 
Ostrapoda. 

ENTOZO'A  (evTo?,  within,  fSov,  an 
animal).  Intestinal  worms ;  a  class  of 
articulated  animals,  comprising  the  pa- 
rasites which  inhabit  the  internal  parts 
of  other  animals. 

EN'TROCHI  (hv,  in,  TPoXor,  a  wheel). 
A  genus  of  fossils,  consisting  of  several 
round  joints,  which,  when  detached  from 
one  another,  are  called  trochitcs.  They 
seem  to  be  the  petrified  arms  of  that 
singular  species  of  the  sea  star-fish, 
called  Stella  arborescens. 

E'OCENE  (nw9,  the  dawn,  kcuvop,  re- 
cent). A  designation  of  the  lowest  divi- 
sion of  the  tertiary  strata,  containing  an 
extremely  small  per  centage  of  living 
species  among  its  fossil  shells,  which  in- 
dicates the  first  commencement,  or  dawn, 
of  the  existing  state  of  the  animate  crea- 
tion. 

E'PACT  (^raK-rop,  adscititious).  A 
term  applied,  in  Astronomy,  to  the  num- 
ber of  days  by  which  the  solar  year  ex- 
ceeds the  lunar.  The  year  of  365£  days, 
contains  twelve  lunations  and  nearly 
eleven  days  more ;  so  that,  were  it  to 
begin  with  the  new  moon,  she  would  be 
eleven  days  old  on  the  first  day  of  the 
succeeding  year ;  the  next  year  she 
would  be  twenty-two  days ;  and  on  the 
third  new  year's  day  she  would  have 


EPI 


EPI 


passed  a  whole  lunation,  and  about  three 
days  more.  The  age  of  the  moon  (thus 
varying)  on  the  first  day  of  any  year  is 
termed  the  Epact. 

EPI-  {kiri).  A  Greek  preposition,  with 
the  radical  signification  of  upon ;  hut  de- 
noting also,  in  some  compounds,  over,  all 
through,  besides. 

1.  Ep-agomince  (kirayo/jievai  rjjuepcu,  in- 
tercalated days).  A  term  applied  to  the 
five  days  which  were  added  by  the  Egyp- 
tians to  their  calendar  at  the  end  of  each 
year,  to  complete  the  number  of  365. 
At  the  end  of  every  fourth  year,  a  sixth 
epagomene  was  added,  to  remedy  the  in- 
convenience arising  from  the  six  hours 
still  remaining  at  the  completion  of  every 
year. 

2.  Epi-genesis  (yeveais,  generation).  A 
term  applied  to  a  theory  of  non-sexual 
generation,  in  which  each  new  germ  is 
an  entirely  new  production  of  the  parent 
organism.    See  Evolution. 

3.  Ep-hemeridce  {hpepa,  a  day).  A 
group  of  Neuropterous  insects,  named 
from  the  ephemera,  or  day-fly,  which  are 
aquatic  in  their  preparatory  states,  and 
emerge  from  the  water  to  undergo  their 
final  metamorphosis.  The  ephemera  is 
so  named  from  its  last  stage  of  existence 
being  generally  limited  to  twenty-four 
hours. 

4.  Ep-hemeris  (rj/iepa,  a  day).  A  term 
applied  to  an  astronomical  table  or  al- 
manac which  assigns  the  place  of  a  planet 
for  a  number  of  successive  days. 

5.  Epi-blastus  (/3\ao-To?,  germen,  a 
shoot).  A  term  applied  by  Richard  to  a 
peculiar  appendage  which  occasionally 
occurs  in  the  monocotyledonous  embryo, 
in  the  form  of  an  anterior  cotyledon. 

6.  Epi-caridians  (/capir,  a  shrimp).  A 
family  of  Tsopodous  crustaceans,  which 
are  parasitic  upon  shrimps. 

7.  E pi-carp  (/<ap7r6?,  fruit).  The  ex- 
terior portion  of  the  pericarp,  commonly 
termed  the  skin  of  the  fruit. 

8.  Epi-cycle  {kvk\o<:,  a  circle).  Literally, 
a  circle  upon  a  circle.  The  ancient 
astronomers  supposed  that  the  motions 
of  the  heavenly  bodies  must  necessarily 
be  in  circles  :  and  in  order  to  make  that 
doctrine  tally  with  observation,  they  in- 
vented, in  succession,  the  two  theories  of 
Epicycles^  and  Eccentrics.  In  the  former, 
called  also  the  Concentric  Theory,  the 
earth  was  supposed  to  be  placed  in  the 
centre  of  a  circle,  on  the  circumference  of 
which  the  centre  of  another  circle  re- 
volved; and  on  the  circumference  of  this 
second  circle  (called  an  Epicycle)    the 

123 


planet  was  imagined  to  move  :  a  suppo- 
sition which  accounted  in  some  degree 
for  the  apparent  irregularities  of  its  mo- 
tion. The  primary  circle  was  called  the 
Deferent.  In  the  Eccentric  Theory,  the 
earth  was  also  placed  stationary  in  the 
centre  of  the  starry  sphere  ;  but  the  sun 
was  carried  round  in  a  circle,  the  centre 
of  which  was  eccentric  from  that  of  the 
earth. 

9.  Epi-cycloid  (nvuKoeidrir,  circular). 
If  a  circle  roll  upon  the  circumference  of 
another  circle  instead  of  a  straight  line, 
points,  either  on,  within,  or  without  its 
circumference,  if  on  the  same  plane,  will 
form  varieties  of  Epicycloids. 

10.  Epi-dermis  {deppa,  skin).  The  ex- 
ternal covering  of  the  skin,  eommonly 
called  cuticle,  in  plants  and  animals. 
Also  the  outer  rough  coating  of  shells, 
over  which  it  is  spread  as  a  fibrous  horny 
skin,  though  destitute  of  sensation. 

11.  Epi-dote  (3i'3&)/x<,  to  give).  A  sub- 
species of  prismatoidal  augite,  also  termed 
acanticone  and  pistacite,  occurring  in 
primitive  beds  and  veins.  The  name  is 
said  to  be  derived  from  an  enlargement 
of  the  base  of  the  prism  in  one  direction, 
the  prefix  here  denoting  besides. 

12.  Epi-gene  crystals  {yevos,  a  kind). 
Substances  found  naturally  crystallized 
in  a  form  which  does  not  belong  to  them- 
selves, but  to  some  other  compound  of 
the  same  base  :  thus,  crystals  of  oxide  of 
iron  are  found  with  the  form  of  sulphuret 
or  carbonate  of  iron.  In  these,  it  appears 
that  the  crystals  must  have  undergone  a 
chemical  change,  unaccompanied  by 
change  of  form. 

13.  Epi-geous  (in,  the  earth).  A  term 
applied  to  the  situation  of  plants,  when 
they  grow  close  upon  the  earth ;  and  to 
those  cotyledons  which  emerge  from  the 
ground,  and  assume  the  colour  of  leaves. 

14.  Epi-gonium  {yovrj,  the  seed).  A 
membranous  bag  which  encloses  the 
conceptacle  or  capsule  of  Jungermannia, 
and  is  ruptured  as  the  latter  elongates. 
It  is  somewhat  analogous  to  the  calyptra 
of  Mosses,  but  is  not  carried  up  on  the 
summit  of  the  capsule. 

15.  Epi-gynous  {ywrj,  a  woman).  That 
condition  of  the  stamens  of  a  plant,  in 
which  they  adhere  both  to  the  calyx  and 
the  ovarium,  appearing  to  be  inserted 
upon  the  summit  of  the  ovarium,  as  in 
umbelliferous  plants. 

16.  Epi-meral  (/uepoc,  a  part  or  limb). 
A  term  applied  to  the  part  of  the  seg- 
ment of  an  articulate  animal  which  is 
above  the  joint  of  the  limb. 

G2 


EPO 


EQU 


17.  Epi-phlceum  (^Xotoc ,  bark).  A  term 
applied  by  Link  to  the  second  portion  of 
the  bark  of  plants,  consisting  of  several 
layers  of  thin-sided  tubular  cells,  rarely 
coloured  green.  This  is  the  phlceum  or 
peridermis  of  Mohl. 

18.  Epiphragma  {(ppafna,  a  fence).  A 
term  applied,  in  Bryology,  to  the  mem- 
brane (peristomium)  which  sometimes 
closes  up  the  orifice  of  the  theca.  It  is 
sometimes  called  tympanum,  from  the 
drum-like  appearance  which  the  theca 
thus  presents. 

19.  Epi-phyllospermous  (<pv\\ov,  a  leaf, 
a-rrepua,  seed).  An  old  term  for  those 
plants  which  bear  their  organs  of  repro- 
duction upon  the  back  of  their  fronds,  as 
the  ferns.  These  are  now  called  dorsi- 
ferous, from  dorsum,  the  back,  and  fero, 
to  bear. 

20.  Epi-phyllous  {cpvWov,  a  leaf).  A 
term  applied  to  any  thing  which  is  in- 
serted upon  the  leaf  of  a  plant. 

21.  Epi-phyie  (Qvtov,  a  plant).  A  plant 
which  grows  upon  other  plants,  adhering 
to  their  bark,  and  rooting  among  the 
scanty  soil  found  on  their  surface.  The 
term  is  generally  restricted  to  those  Or- 
chidaceous plants  which  grow  upon  trees. 
The  old  term  was  epidendrum. 

22.  Epi-pterous  (mepov,  a  wing).  A 
term  applied  to  a  fruit  or  seed  which  is 
furnished  with  a  broad  margin  or  wing, 
when  it  terminates.    See  Pterous. 

23.  Epi-rrheology  (emppoij,  a  flowing 
on,  \6yos,  description).  That  branch  of 
science  which  treats  of  the  effects  of  ex- 
ternal agents  upon  living  plants. 

24.  Epi- sperm  {wnepixa,  seed).  The 
terms  episperm  and  perisperm  are  ap- 
plied by  Richard  to  the  testa,  or  integu- 
ment of  a  seed — the  spermoderm  of  De 
Candolle. 

25.  Epi-zoa  {&ov,  an  animal).  An 
order  of  the  Entozoa,  which  are  at  first 
free  and  natant  larvae,  afterwards  fix- 
ing themselves  permanently,  by  strong 
organs  of  attachment,  to  the  soft  super- 
ficial parts  of  aquatic  animals. 

EPI'STOLOGRA'PHIC  WRITING 
(kni<TTo\ri,  a  letter,  ypdcpoo,  to  write).  A 
designation  of  the  demotic  or  enchorial 
mode  of  writing,  in  common  use  among 
the  Egyptians,  and  approaching  very 
nearly  to  the  Chinese  method. 

E'POCH  (67rox»/,  a  pause  in  the  reck- 
oning of  time).  In  Chronology,  a  point 
at  which  one  period  closes  and  another 
begins.  The  epoch  of  a  star  is  its  place 
in  the  heavens.  In  order  to  predict  the 
longitude  of  a  planet  at  any  epoch,  some 
124 


preceding  epoch  must  be  taken,  at  which 
the  longitude  is  known.  The  latter  is 
emphatically  called  the  epoch;  and  the 
term  longitude  at  the  epoch  has  been 
shortened  into  epoch. 

EQUATION  (in  Astronomy).  The 
term  applied  by  astronomers  to  their 
practice  of  reducing  all  their  observations, 
both  of  right  ascension  and  of  declina- 
tion, to  vsome  common  and  convenient 
epoch.  These  corrections,  or  equations, 
are  necessary  in  consequence  of  the 
elliptic  figure  of  the  moon's  orbit,  the 
sun's  attraction,  and  other  causes. 

1.  By  equating  the  observation  for  nuta- 
tion, is  meant  the  getting  rid  of  a  periodi- 
cal cause  of  fluctuation,  and  present- 
ing a  result,  not  as  it  was  observed,  but 
as  it  would  have  been  observed,  had 
that  cause  of  fluctuation  had  no  exist- 
ence. 

2.  Equation  of  time.  In  popular  lan- 
guage, this  expression  denotes  the  differ- 
ence between  the  times  indicated  by  an 
accurately  constructed  sun-dial  and  a 
well-regulated  clock.  Astronomically,  it 
signifies  the  difference,  expressed  in 
mean  solar  time,  between  the  true  or 
apparent  right  ascension  of  the  sun  and 
its  mean  right  ascension.  There  are  only 
four  days  in  the  year,  when  the  apparent 
and  the  mean  time  coincide,  and  the 
equation  of  time  is  nothing,  viz.  April  15th, 
June  15th,  September  1st,  and  Decem- 
ber 24th.  Between  April  15th  and  June 
15th,  the  clock  is  earlier  than  the  sun,  and 
the  equation  is  subtractive ;  between 
June  15th  and  September  1st,  the  clock 
is  later  than  the  sun,  and  the  equation 
is  additive. 

EQUATION  (in  Mathematics).  An 
assertion  of  the  equality  of  two  magni- 
tudes, represented  by  the  symbol  =.  It 
is  of  two  kinds,  viz.  an  equation  of  con- 
dition, which  will  be  true  only  on  the 
supposition  of  certain  conditions,  as 
2a  +  1  =  13,  which  requires  that  a  should 
represent  6 ;  or  an  identical  equation, 
which  is  true  independently  of  all  condi- 
tions, i.  e.  whatever  may  be  the  value  of 
the  symbols  employed,  as  a  +  a  =  2a. 

EQUA'TION,  ALGEBRA'IC.  An 
expression  of  two  algebraic  quantities, 
when  connected  together  by  the  sign  of 
equality.  The  solution  of  an  equation  is 
the  operation  by  which  the  values  of  the 
unknown  quantities  are  found  in  terms 
of  the  known  quantities.  If  the  equation 
contains  no  power  of  the  unknown  quan- 
tities, but  these  quantities  merely  in 
their  simplest  fonn,  it  is  called  a  simple 


EQU 


EQU 


equation ;  if  it  contains  the  square  of  the 
unknown  quantity,  it  is  called  a  quadratic 
equation  ;  if  the  cube  of  the  unknown 
quantity,  a  cubic  equation  ;  if  the  fourth 
power,  a  biquadratic,  &c. 

Equation,  Quadratic.  This  is  pure  or 
adfected.  1.  Pure  quadratic  equations 
are  those  which  contain  only  the  square 
of  the  unknown  quantity,  as  x2  =  36. 
2.  Adfected  quadratic  equations  are  those 
which  involve  hoth  the  square  and  the 
simple  power  of  the  unknown  quantity, 
as  x*  +  4x  =  45. 

EQUATION  OF  PAYMENTS.  An 
arithmetical  rule  for  finding  the  mean 
time  for  paying  the  amount  of  several 
sums  which  are  due  at  different  times. 
Rule: — Multiply  each  term  by  its  time, 
and  divide  the  sum  of  the  products  by 
the  whole  debt ;  the  quotient  is  accounted 
the  mean  time. 

EQUATOR  {aequo,  to  make  equal). 
The  Great  Circle  on  the  earth's  surface, 
every  point  in  which  is  equally  distant 
from  the  poles.  It  divides  the  earth  into 
two  equal  parts,  the  one  being  called  the 
Northern,  the  other  the  Southern  Hemi- 
sphere.    See  Equinoctial. 

EQUATO'RIAL.  An  apparatus,  for- 
merly called  a  parallactic  instrument, 
used  for  all  those  astronomical  observa- 
tions which  require  an  object  to  be  kept 
long  in  view.  Its  value  consists  in  its 
being  capable,  when  once  set  upon  an 
object,  of  following  the  object  for  an  inde- 
finite period  by  a  single  motion,  i.  e.  by 
merely  turning  the  whole  apparatus 
round  on  its  polar  axis. 

EQUATO'RIAL  CURRENT.  Adrift- 
current  which  traverses  the  Atlantic 
Ocean,  named  from  its  course  lying  under 
or  near  the  line.  It  is  supposed  to  be 
formed  in  the  Bay  of  Benin,  whence  it 
proceeds  westward  on  both  sides  of  the 
equator,  as  far  as  22°  W.  long. ;  it  then 
declines  somewhat  southward  towards 
the  Brazilian  coast,  and  separates  into 
two  currents,  called  the  Guiana  current 
and  the  Brazil  current. 

EQUIA'NGULAR  {cequus  angulus, 
equal  angle).  As  applied  to  a  single 
geometrical  figure,  the  term  denotes  that 
all  its  angles  are  equal,  as  in  all  regular 
polygons;  as  applied  to  two  figures  of 
the  same  kind,  it  denotes  that  the  cor- 
responding angles  of  the  two  figures  are 
equal,  though,  separately,  they  may  not 
be  equiangular  figures. 

E'QUIDjE  (equus,  a  horse).  The  Horse 
tribe;  the  solidungulous  family  of  pachy- 
dermatous animals,  with  only  one  ap- 
125 


parent   toe   and  a  single  hoof  to  each 
foot. 

EQUILATERAL  {aqua  latera  ha- 
bens).  A  term  applied  to  a  geometrical 
figure  bounded  by  equal  sides. 

EQUILIBRIUM  {ceque,  equally,  libro, 
to  poise).  A  term  expressive  of  the 
equable  diffusion  of  temperature  which 
all  bodies  on  the  earth  tend  to  produce  ; 
and  of  the  equal  distribution  of  the  elec- 
tric fluid  in  its  natural  undisturbed  state. 
Equilibrium  of  forces.  When  two  forces 
counteract,  or  balance  each  other,  they 
are  said  to  be  in  equilibrio.  To  produce 
this  state  in  solid  bodies,  it  is  only  neces- 
sary to  support  the  centre  of  gravity  :  a 
pair  of  scales  are  in  equilibrio,  when  the 
beam  is  in  a  horizontal  position. 

EQUIMULTIPLES.  The  products  of 
quantities  multiplied  by  the  same  num- 
ber. Thus  six  times  A  and  six  times  B 
are  egwi-multiples  of  A  and  B;  m*np 
and  m*  nq  are  equi-multiples  of  p  and  q; 
a  league  and  a  yard  are  equimultiples  of 
a  mile  and  a  foot. 

EQUINO'CTIAL.  A  synonymous  term 
for  the  equator,  because,  when  the  sun 
is  in  the  plane  of  it,  nodes  cequantur,  it 
is  equal  day  and  night  over  the  whole 
world. 

EQUINO'CTIAL  POINTS.  The  two 
points  of  the  ecliptic  where  the  equi- 
noctial or  equator  crosses  it;  viz.,  in  the 
first  point  of  Aries  and  the  first  of  Libra. 
The  times  of  the  year  answering  to  these 
points  are  called  Vernal  and  Autumnal 
Equinoxes,  the  one  happening  in  the 
spring,  the  other  in  the  autumn;  the 
vernal  being  that  at  which  the  sun 
crosses  the  equinoctial  from  south  to 
north;  the  autumnal,  when  it  quits  the 
northern  and  enters  the  southern  hemi- 
sphere.    See  Precession. 

EQUISETA'CEjE.  Leafless  branched 
plants,  with  a  striated  fistular  stem.  i»- 
florescence  consisting  of  peltate  scales. 
Reproductive  bodies  in  the  inside  of  the 
lobes  of  the  scales,  consisting  of  four 
club-shaped  bodies,  enveloping  a  naked 
spore. 

EQUISE'TIC  ACID.  A  peculiar  acid, 
existing,  in  combination  with  magnesia, 
in  the  Equisetum  fluviatile. 

EQUIVALENTS,  CHEMICAL  {esqud, 
equally,  valeo,  to  avail).  A  term  applied 
by  Wollaston  to  the  combining  propor- 
tions of  elementary  and  compound  sub- 
stances, as  the  quantities  of  acid  and 
base,  in  salts,  required  to  neutralize  each 
other.  The  following  are  instances  of 
this  law  :— 

G3 


ERA 


ERA 


Arsenic  acid. .  57*68    Lime 28 

Muriatic  acid   37         Magnesia...  20 

Nitric  acid  ...  54         Potash 48 

Sulphuric  acid  40         Soda 32 

Thus  57*68  of  arsenic  acid,  37  of  muri- 
atic, 54  of  nitric,  and  40  of  sulphuric, 
comhine  with  28  of  lime,  forming,  re- 
spectively, a  neutral  arseniate,  muriate, 
nitrate,  and  sulphate  of  lime  ;  &c.  &c. 

E'QUIVALVED.  A  term  applied  to 
hivalves,  when  the  two  valves  are  of 
equal  size  and  depth. 

EQUI'VOCAL  NOUN  (aqud,  equally, 
voco,  to  call).  In  Logic,  a  noun  which  has 
more  than  one  signification,  each  of  its 
significations  being  equally  applicable  to 
several  objects,  as  bull — the  animal ;  the 
pope's  official  letter ;  a  blunder.  "  Strictly 
speaking,  there  is  hardly  a  word  in  any 
language  which  may  not  be  regarded,  as 
in  this  sense,  equivocal ;  but  the  title  is 
usually  applied  only  in  any  case  where  a 
word  is  employed  equivocally ;  e.  g.  where 
the  middle  term  is  used  in  different 
senses  in  the  two  premises  ;  or  where  a 
proposition  is  liable  to  be  understood  in 
various  senses,  according  to  the  various 
meanings  of  one  of  its  terms." — Whately. 
EQUU'LEUS  PICTO'RIS.  The  Paint- 
er's Horse,  or  Easel ;  a  modern  southern 
constellation,  consisting  of  eight  stars, 
situated  close  to  the  principal  star  of  Argo. 
E'QUULUS.  The  Horse's  Head;  a 
northern  constellation,  consisting  of  ten 
stars. 

E'RA  or  iERA.  A  fixed  point  of  time, 
at  which  the  computation  of  ensuing 
years  is  commenced.  The  following  are 
the  principal  eras  : — 

1.  Era  of  the  Olympiads.  The  most 
ancient  method  of  computing  time,  first 
instituted  in  the  year  b.c.  776,  and  con- 
sisting of  a  revolution  of  four  years.  It 
originated  from  the  Olympic  games, 
which  were  celebrated  every  fifth  year 
at  Olympia,  a  city  of  Elis  in  Greece. 

2.  Era  of  the  Foundation  of  Rome. 
This  has  been  variously  fixed.  The 
Varronian  computation,  which  fixes  it  in 
the  year  b.c  753,  was  adopted  by  the 
Roman  emperors,  and  has  received  the 
sanction  of  most  modern  chronologists. 

3.  Christian  Era.  This  commenced 
Jan.  1,  in  the  middle  of  the  fourth  year 
of  the  194th  Olympiad,  the  753rd  of  the 
building  of  Rome,  and  the  4714th  of  the 
Julian  period.  The  years  of  this  era  are 
described  in  ancient  documents  as  the 
years  "  of  Grace,"  of  "  the  Incarnation," 
of  "  the  Nativity,"  of  "  the  Circumcision," 
and  "annus  Trabeationis." 


4.  Julian  Era.  The  era  of  the  reform- 
ation of  the  Roman  Calendar  by  Julius 
Caesar,  who  ordained  that  the  year  of 
Rome  707  should  consist  of  15  months, 
forming  altogether  445  days;  that  the 
ensuing  year,  708,  should  consist  of  365 
days ;  and  that  every  fourth  year  should 
contain  366  days,  the  additional  day 
being  introduced  after  the  6th  of  the 
calends  of  March,  i.e.  the  24th  of  Febru- 
ary, which  year  he  called  bissextile,  be- 
cause the  6th  of  the  calends  of  March 
was  then  doubled. 

5.  The  Indictions.  The  Indictions 
consisted  of  a  revolution  of  fifteen  years, 
which  are  separately  reckoned  as  Indic- 
tion  1,  Indiction  2,  &c,  up  to  15,  when 
they  recommence  with  1.  The  first  In- 
diction is  usually  referred  to  the  year 
A.D.  313.     See  Indictions. 

6.  Mundane  Era  of  Alexandria.  The 
Alexandrian  era  of  the  Creation  of  the 
World  was  fixed  at  5502  years  before 
Christ.  This  computation  was  continued 
until  a.d.  284,  or  the  year  5786  of  the 
Alexandrian  era;  but  in  the  following 
year,  ten  years  were  subtracted,  and  that 
year  was  accordingly  a.  alex.  5777. 

7.  Mundane  Era  of  Antioch.  By  this 
era,  the  Creation  of  the  World  was  fixed 
at  5492  years  before  Christ,  or  ten  years 
later  than  by  the  era  of  Alexandria.  As, 
however,  ten  years  were  subtracted  from 
the  Alexandrian  era  in  a.d.  285,  the  two 
eras  thenceforward  coincided. 

8.  Era  of  Constantinople.  This  era 
refers  the  Creation  of  the  World  to  the 
5508th  year  before  Christ,  and  is  still 
used  by  the  Greek  Church.  In  this  era 
there  are  two  years  :  the  civil,  which  be- 
gins with  the  month  of  September ;  and 
the  ecclesiastical,  which  commences  on 
the  21st  of  March,  and  sometimes  on  the 
1st  of  April. 

9.  Era  of  the  Seleucidce.  This  era, 
also  called  the  "Era  of  the  Greeks," 
sometimes  the  "  Era  of  Alexandria,"  and 
occasionally  the  "  Era  of  the  Syro- 
Macedonians,"  commenced  in  the  year 
of  Rome  442,  twelve  years  after  the 
death  of  Alexander,  and  311  years  and 
4  months  before  the  birth  of  Christ,  being 
the  epoch  of  the  conquest  of  Babylon  by 
Seleucus  L,  surnamed  Nicator,  or  the 
"Victorious.  It  is  still  used  in  the  Levant. 

10.  C cesarean  Era  of  Antioch.  This 
era  was  instituted  at  Antioch,  in  conse- 
quence of  the  victory  gained  by  Julius 
Caesar  in  the  plain  of  Pharsalia,  on  the 
9th  of  August,  in  the  year  of  Rome  706, 
and  48  years  before  Christ. 


ERA 


ERI 


11.  Era  of  Pisa.  This  era,  which  was 
sometimes  used  in  France,  especially  in 
the  twelfth  century,  differed  from  our 
common  era  by  preceding  it  by  one  year 
only. 

12.  Era  of  Spain.  An  era  founded  in 
consequence  of  the  conquest  of  Spain  by 
Augustus,  in  the  year  of  Rome  715, 
thirty -nine  years  before  the  birth  of 
Christ.  The  era  commenced  Jan.  1, 
a.u.c.  716,  and  38  B.C.  It  prevailed  in 
Portugal  so  lately  as  1415,  if  not  until 
1422. 

13.  Era  of  Diocletian,  or  of  the  Mar- 
tyrs. This  era  dates  from  August  29, 
a.d.  281,  the  day  when  Diocletian  was 
proclaimed  emperor  at  Chalcedon ;  and 
in  consequence  of  his  persecution  of  the 
Christians,  it  is  also  called  the  "  Era  of 
the  Martyrs."  It  was  generally  used  by 
Christian  writers  until  the  introduction 
of  the  Christian  era  in  the  sixth  century, 
and  it  is  still  used  by  the  Ethiopians  and 
Copts. 

14.  Era  of  the  Hegira.  This  era,  also 
called  the  "  Era  of  the  Turks,  Arabs,  and 
other  Mahomedans,"  commences  on  Fri- 
day, July  16,  a.d.  622,  the  day  of  the 
flight  of  Mahomet  from  Mecca  to  Medina, 
which  is  the  date  of  the  Mahomedans ; 
but  astronomers  and  some  historians 
assign  it  to  the  preceding  day — an  im- 
portant fact,  to  be  borne  in  mind  when 
perusing  Arabian  writers. 

15.  Era  of  Abraham.  This  era  pre- 
ceded the  birth  of  Christ  by  2015  years, 
and  began  on  the  1st  of  October,  2016. 

16.  Era  of  Nabonassar.  The  author  of 
this  era  was  Nabonassar,  the  founder  of 
the  kingdom  of  Babylon.  It  commenced 
on  Wednesday,  Feb.  26,  in  the  3967th 
year  of  the  Julian  period,  i.e.  b.c.  747. 
It  included  a  period  of  424  Egyptian 
years,  from  the  commencement  of  Na- 
bonassar's  reign  to  the  death  of  Alexan- 
der the  Great,  and  was  thence  brought 
down  to  the  reign  of  Antoninus  Pius. 

17.  Era  of  Tyre.  This  era  began  125 
years  before  Christ,  in  the  year  of  Rome 
628,  and  in  the  186th  year  of  the  era  of 
the  Seleucidae. 

18.  Actiatic  Era.  This  era  is  founded 
on  the  battle  of  Actium,  which  rendered 
Augustus  master  of  the  Roman  empire. 
The  Romans  commenced  this  era  on  the 
1st  of  January,  a.u.c.  724,  and  in  the 
16th  of  the  Julian  era.  In  Egypt,  it 
commenced  in  the  same  year  as  that  of 
the  battle,  and  prevailed  until  the  reign 
of  Diocletian.  The  Greeks  of  Antioch 
used  it  as  late  as  the  ninth  century. 

127 


19.  Era  of  Augustus.  This  was  later 
by  four  years  than  the  Actiatic  era,  and 
began  in  the  year  of  Rome  727,  twenty- 
seven  years  before  the  Christian  era. 

20.  Era  of  the  Ascension.  This  era  is 
supposed  to  have  been  used  only  by  the 
author  of  the  Chronicle  of  Alexandria, 
who  dates  the  year  of  the  Martyrdom  of 
St.  Menas  of  Cotys  at  the  period  corre- 
sponding with  the  12th  of  November, 
a.d.  295. 

21.  Era  of  the  Armenians.  This  era 
commenced  on  Tuesday,  July  9th,  a.d. 
552,  the  period  when  the  Council  of 
Tiben,  or  the  Armenians,  confirmed  the 
condemnation  of  the  Council  of  Chalce- 
donia,  which  was  pronounced  in  a.d.  536, 
and  by  which  they  completed  their 
schism. 

22.  Era  of  Tezdegird  III.,  or  the  Per- 
sian Era.  This  era  commenced  on  the 
accession  of  Yezdegird  to  the  throne  of 
Persia,  on  the  16th  of  June,  a.d.  632. 

23.  Jewish  Era.  This  era  is  commonly 
supposed  to  be  not  more  ancient  than  the 
fifteenth  century.  The  Jews  now  date 
from  the  creation  of  the  world,  which 
they  consider  to  have  taken  place  3760 
years  and  3  months  before  the  commence- 
ment of  the  Christian  era. 

24.  Era  of  the  Caliyug.  This  is  the 
most  ancient  era  of  India,  and  dates  from 
a  period  3101  years  before  Christ.  Other 
eras  are  used  in  different  parts  of  India, 
as  those  of  Salivahana,  of  Vicramaditya, 
of  Parasurama,  &c. 

25.  Era  of  the  French.  The  era  of  the 
National  Convention,  which  commenced 
on  the  22nd  of  September,  1792,  being 
the  epoch  of  the  foundation  of  the  Re- 
public ;  but  its  establishment  was  not 
decreed  till  the  4th  "  Frimaire"  of  the 
year  u.  (Nov.  24, 1793.)  Two  days  after- 
wards the  public  acts  were  thus  dated. 
This  calendar  existed  till  the  10th  "  Ni- 
vose,"  of  the  year  xiv.  (Dec.  31,  1805,) 
when  the  Gregorian  mode  of  computation 
was  restored. 

E'REMACAU'SIS  (^pe/xop,  slow,  Kav- 
o-if,  burning).  A  term  applied  by  Liebig 
to  the  slow  combustion  or  oxidation  of 
organic  matters  in  air,  as  the  conversion 
of  wood  into  humus,  the  formation  of 
acetic  acid  from  alcohol,  nitrification,  &c. 

ERICA'CE.®  (erica,  a  heath).  The 
Heath  tribe  of  Dicotyledonous  plants. 
Shrubs,  with  leaves  evergreen,  rigid,  en- 
tire, whorled  or  opposite ;  flowers  mono- 
petalous,  regular ;  stamens  definite ;  ova- 
rium superior,  many-seeded ;  seeds  apte- 
rous. 

G4 


ER  Y 

ERI'DANUS.  A  southern  constella- 
tion, consisting  of  84  stars,  the  principal 
of  which  is  Achernar. 

ERINACE'AD^i.  The  Urchin  or 
Hedgehog  tribe ;  a  family  of  insectivor- 
ous vertebrata,  which  are  remarkable  not 
only  for  their  covering  of  spines,  but  for 
the  great  development  of  the  muscular 
envelope  of  the  body  immediately  beneath 
the  skin. 

E'RINITE.  A  heautiful  emerald-green 
arseniate  of  copper,  named  from  its  being 
found  in  the  county  of  Limerick  in  Ire- 
land. 

ERTO'METER  {epiov,  wool,  p.erpov,  a 
measure).  An  instrument,  invented  by 
Dr.  Young,  for  the  purpose  of  measuring 
the  diameters  of  minute  fibres. 

E'RLAMITE.  A  new  mineral,  forming 
a  part  of  the  oldest  gneiss  formation. 

ERO'SE  (erosus,  gnawed  off).  Gnawed; 
having  the  margin  irregularly  divided,  as 
if  bitten  by  an  animal :  a  term  applied  to 
the  margin  of  certain  leaves. 

ERRA'NTES  (erro,  to  wander).  A 
term  applied  by  M.  Edwards  to  an  order 
of  the  Anellida,  which  are  at  once  the 
highest  organized  and  the  most  locomo- 
tive. These  are  the  dorsibranchiata  of 
Cuvier,  and  are  commonly  known  by  the 
names  of  sea-centipedes,  sea-mice,  or 
nereids. 

ERRATIC  BLOCKS.  A  term  syno- 
nymous with  boulders,  derived  from  their 
wide  distribution  over  the  surface  of  the 
earth.    See  Boulders. 

ERY'THRO-  (epuflpor,  red).  A  Greek 
term  employed  in  composition  to  denote 
any  pure  red  colour.  It  agrees  with  the 
ruber  of  the  Latins. 

1.  Erythric  Acid.  A  red  substance  pro- 
duced by  the  mutual  action  of  the  nitric 
and  uric  acids.  Dr.  Prout  considers  it 
to  be  not  a  peculiar  acid,  but  a  com- 
pound of  nitric  and  purpuric  acid  and 
ammonia. 

2.  Erythrin.  One  of  a  series  of  sub- 
stances including  erythrilin,  erythrin 
bitter  or  amarythrin,  telerythrin,  &c, 
obtained  by  Dr.  Kane  from  the  Roccella 
tinctoria. 

3.  Erythro-gen  (yewdco,  to  produce). 
A  green-coloured  substance  found  in  the 
gall-bladder,  in  a  case  of  jaundice.  It 
unites  with  nitrogen,  and  produces  a  red 
compound. 

4.  Erythro-phylle  ((pvXKov,  a  leaf).  A 
term  applied  by  Berzelius  to  the  red 
colouring  matter  of  leaves  and  fruits  in 
autumn. 

5.  Erythro-stomum  (o-Toyua,  a  mouth). 

128 


EST 

A  terra  applied  by  Desvaux  to  the 
aggregate  fruit,  more  generally  termed 
etcerio. 

ESCA'RPMENT  (escarper,  to  cut 
steep).  The  abrupt  face  of  a  ridge  of 
high  land,  where  subjacent  strata  are 
observed  to  "  crop  out." 

ESO'CIDiE  (esox,  the  pike).  The  Pike 
tribe ;  a  family  of  Malacopterygious  or 
soft-spined  fishes,  having  the  ventral 
fins  placed  under  the  abdomen,  and  in- 
cluding most  of  the  voracious  fresh- 
water fishes,  as  well  as  several  important 
marine  species.  They  are  distinguished 
by  the  position  of  the  dorsal  opposite  to 
the  anal  fin,  and  by  the  absence  of  fatty 
matter  in  the  former. 

ESOTE'RIC  (Wrep<K6f,  inner).  A 
term  applied  to  the  disciples  of  Pytha- 
goras, Aristotle,  &c,  who  were  scientifi- 
cally taught,  as  distinguished  from  the 
exoteric,  who  had  merely  popular  views. 
The  term  esoteric  is  sometimes  applied  to 
a  mysterious  doctrine,  which  was  taught 
only  to  the  more  enlightened,  and  was 
thus  distinguished  from  the  exoteric,  or 
published  doctrine.  In  this  sense  *1  eso- 
teric" is  synonymous  with  acroamatic, 
or  that  which  is  communicated  by  oral 
instruction. 

E'SSENCE  (essentia,  a  being).  A  scho- 
lastic term  denoting  the  essential  perfec- 
tion of  a  being,  i.  e.  its  entity  and  attri- 
butes. It  sometimes  signifies  merely  the 
principal  attributes  of  a  being. 

ESSENTIAL  DEFINITION.  In  Lo- 
gic, a  definition  which  assigns,  not  the 
properties  or  accidents  of  the  thing  de- 
fined, but  what  are  regarded  as  its  essen- 
tial parts,  whether  physical  or  logical. 
See  Definition. 

ESSENTIAL  OILS.  Oils  obtained  by 
distillation  from  odoriferous  vegetable 
substances.  Several  of  the  volatile  or 
essential  oils  are  called  essences. 

ESTIVA'TION  {ccstivus,  belonging  to 
summer).  Prcefloration.  A  botanical 
term  applied  to  several  modes  in  which 
the  floral  envelopes  are  folded  up  in  the 
un expanded  or  bud  state.  It  is  said 
to  be — 

1.  Involute,  when  the  edges  are  rolled 
inwardly  spirally  on  each  side. 

2.  Revolute,  when  the  edges  are  rolled 
backwards  spirally  on  each  side. 

3.  Obvolute,  when  the  margins  of  one 
leaf  alternately  overlap  those  of  the  oppo- 
site leaf. 

4.  Convolute,  when  one  leaf  is  wholly 
rolled  up  within  another  leaf. 

5.  Supervolute,  when  one  edge  is  rolled 


EST 


ETH 


inwards,  and  is  enveloped  by  the 
opposite  edge  rolled  in  an  opposite  di- 
rection. 

6.  Induplicate,  when  the  margins  are 
bent  abruptly  inwards,  and  the  external 
face  of  these  edges  is  applied  to  each 
other  without  any  twisting. 

7.  Conduplicate,  when  tbe  sides  are 
applied  parallelly  to  the  faces  of  each 
other. 

8.  Plaited,  when  they  are  folded  length- 
wise, like  the  plaits  of  a  closed  fan. 

9.  Replicate,  when  the  upper  part  is 
curved  back  and  applied  to  the  lower. 

10.  Curvative,  when  the  margins  are 
slightly  curved,  either  hackwards  or  for- 
wards, without  any  sensible  twisting. 

11 .  Wrinkled,  when  the  parts  are  folded 
up  irregularly  in  every  direction. 

12.  Imbricated,  when  they  overlap  each 
other  parallelly  at  the  margins,  without 
any  involution. 

13.  Equitant,  when  they  overlap  each 
other  parallelly  and  entirely,  without  in- 
volution, as  in  iris. 

14.  Reclinate,  when  they  are  bent  down 
upon  their  stalk. 

15.  Circinate,  when  they  are  rolled 
spirally  downward. 

16.  Valvate,  when  they  are  applied  to 
each  other  by  the  margins  only. 

17.  Quincuncial,  when  the  pieces  are 
five  in  number,  of  which  two  are  ex- 
terior, two  interior,  and  the  fifth  covers 
the  interior  with  one  margin,  and  has  its 
other  margin  covered  by  the  exterior,  as 
in  the  rose. 

18.  Twisted,  which  is  the  same  as 
contorted,  except  that  there  is  no  obli- 
quity in  the  form  or  insertion  of  the 
pieces. 

19.  Contorted,  when  they  are  twisted 
in  such  a  manner  that  each  piece  of  a 
whorl  overlaps  its  neighbour  by  one 
margin,  and  is  overlapped  by  its  other 
neighbour  by  the  other  margin. 

20.  Alternative,  when  the  pieces  being 
in  two  rows,  the  inner  is  covered  by  the 
outer  in  such  a  way  that  each  of  the 
exterior  rows  overlaps  half  of  two  of  the 
interior,  as  in  liliaceae. 

21.  Vexillary,  when  one  piece  is  much 
larger  than  the  others,  and  is  folded  over 
them,  they  being  arranged  face  to  face, 
as  in  papilionaceous  flowers. 

22.  Cochlear,  when  one  piece,  being 
larger  than  the  others,  and  hollowed  like 
a  helmet  or  bowl,  covers  all  the  others, 
as  in  aconite,  some  species  of  personate 
flowers,  &c. — Lindley. 

ESTUARIES    {cestus,  the  tide).    In- 
129 


lets  of  the  land,  which  are  entered  by 
tides  of  the  sea  and  by  rivers.  They 
occur  in  the  Thames,  the  Severn,  the 
Tay,  &c. 

ETiE'RIO  (eTaipeia,  an  association). 
A  term  applied  by  Mirbel  to  an  aggre- 
gate fruit,  the  separate  parts  of  which 
are  achaenia,  as  in  ranunculus,  rubus, 
fee. 

ETE'SIAN  WIND  (ei^o-toc,  annual). 
A  northerly  or  north-easterly  wind  which 
prevails  very  much  in  summer  all  over 
Europe.     See  Winds. 

E'THAL.  A  peculiar  oily  substance, 
obtained  from  spermaceti ;  also  termed 
hydrate  of  oxide  of  cetyl.  The  term  is 
formed  of  the  first  syllable  of  the  words 
ether  and  a/cohol,  on  account  of  its  ana- 
logy to  these  liquids  in  point  of  compo- 
sition. 

ETHER  (a\9rjp,  ether).  An  imaginary 
fluid,  supposed  by  some  philosophers  to 
fill  all  space  beyond  the  atmospheres  of 
the  earth  and  other  planets. 

ETHER  (in  Chemistry).  A  very  vola- 
tile fluid,  produced  by  the  distillation 
of  alcohol  with  an  acid.  It  is  some- 
times distinguished  as  sulphuric  ether, 
from  the  mode  of  preparing  it ;  but  when 
well  rectified,  the  ether  is  the  same, 
whatever  acid  has  been  employed. 

ETHE'REUM  (alflJ/p,  ether).  A  hypo- 
thetical carburetted  hydrogen,  so  named 
by  Dr.  Kane,  and  identical  with  the 
ethule  of  Berzelius.  Etherine  is  a 
peculiar  carburetted  hydrogen,  which 
has  also  been  regarded  as  the  basis  of 
ether. 

ETHE'RID^.  River  Oysters;  a  fa- 
mily of  the  atrachian  bivalves,  named 
from  the  genus  etheria. 

ETHICS  (hOiKds,  belonging  to  morals). 
The  science  of  Morals,  or  those  affections 
of  the  mind  which  develop  themselves  in 
action.  Aristotle  derives  the  word  from 
another,  which  signifies  habit  (h9iKrjv 
a7r6  rod  $0ovs),  moral  disposition  being 
formed  upon  habit. 

ETHIO'NIC  ACID  (4i%,  ether,  6elov, 
sulphur).  Ethero- sulphuric  acid.  An 
acid  produced  by  the  action  of  the  vapour 
of  anhydrous  sulphuric  acid  upon  abso- 
lute alcohol  kept  cold. 

ETHIOPIAN  or  NEGRO  RACE.  One 
of  the  five  principal  races  of  mankind,  in 
which  the  head  is  narrow  and  compressed 
at  the  sides,  the  forehead  very  convex, 
the  cheek-bones  projecting  forwards,  the 
nostrils  wide,  the  jaws  lengthened,  the 
skull  in  general  thick  and  heavy,  the 
face  narrow,  projecting  towards  the  lower 
G5 


EUP 


EVE 


part,  the  nose  spread  and  almost  con- 
founded with  the  cheeks,  the  lips,  parti- 
cularly the  upper  one,  very  thick. 

ETHNO'GRAPHY  (gfror,  a  race, 
7pd0w,  to  describe).  A  historical  inves- 
tigation into  the  origin,  migrations,  and 
connexion  of  various  peoples.  In  this 
sense,  ethnography  is  purely  of  a  his- 
torical character,  and  may  be  considered 
as  distinct  from  anthropography.  A  series 
of  anthropograpmes,  of  different  epocns, 
would  form  the  true  basis  of  ethno- 
graphy. 

ETHU'LE  (a\9hp,  ether,  v\n,  matter). 
A  hypothetical  radical,  existing  in  ether 
and  its  compounds ;  ether  being  the 
oxide  of  ethule,  and  alcohol  the  hydrated 
oxide  of  ethule. 

ETIOLATION.  The  process  of  blanch- 
ing plants,  as  celery,  kale,  &c,  by  shel- 
tering them  from  the  action  of  light. 
The  natural  colour  of  the  plants  is  thus 
prevented  from  being  formed. 

ETYMO'LOGY  (to  'drvfiov,  the  deriva- 
tion of  a  word  from  its  root,  \6yos,  an 
account).  That  part  of  Grammar  which 
treats  of  the  formation  of  words.  Under 
this  general  definition  are  included  the 
classification  of  words,  the  various  modi- 
fications they  undergo  to  express  different 
meanings,  and  their  origin  and  history. 

EUCHLORINE  (el,  brilliant,  x^wpop, 
green).  The  name  given  by  Davy  to  the 
protoxide  of  chlorine,  from  its  being  con- 
siderably more  brilliant  than  simple  chlo- 
rine. 

EU'CHRONIC  ACID  (eZxpoo?,  of  a 
fine  colour).  An  acid  procured  by  the 
decomposition  of  the  neutral  mellitate  of 
ammonia  by  heat.  It  forms  a  blue  com- 
pound with  zinc,  called  euchrone. 

EU'CLASE  (el,  well,  K\d<a,  to  break). 
Prismatic  emerald;  a  beautiful  mineral 
found  in  Peru  and  Brazil. 

EUDFALITE.  A  brownish-red  mine- 
ral, belonging  to  the  tessular  system  of 
Mohs. 

EUDIO'METER  (evSia,  calm  weather, 
fxerpov,  a  measure).  An  instrument  for 
ascertaining  the  purity  of  the  air,  or, 
rather,  the  proportion  of  oxygen  con- 
tained in  a  given  gas. 

EUKAIRITE.  A  new  mineral  found 
in  the  copper  mine  of  Skrickerum,  and 
consisting  of  silver,  selenium,  copper, 
and  alumina. 

EUPHE'MISM  (eixpnuia,  the  use  of 
words  of  good  omen).  A  mild  name  for 
a  bad  thing;  a  rhetorical  figure  em- 
ployed to  prevent  giving  offence  to  "  ears 
polite,"  and  adopted,  in  daily  use,  in 
130 


deference    to   the   fastidiousness  which 

prevails  on  certain  points :  "  Strabonem 

Appellat  Pcetum  pater  ;   et  Pullum, 

male  parvus 
Si  cui  filius  est,"  &c. 

EU'PHONY  {elxpuvia,  goodness  of 
voice).  An  agreeable  quality  of  language 
arising  from  the  harmonious  combination 
of  sounds.  It  consists  in  an  uninter- 
rupted flow  of  words,  which  neither  im- 
pedes the  speaker's  utterance,  nor  offends 
the  hearer's  ear ;  and  is  opposed  to  caco- 
phony, or  a  harsh  and  disagreeable  style. 

EUPHORBIA'CEjE.  The  Euphor- 
bium  tribe  of  Dicotyledonous  plants. 
Trees,  shrubs,  and  herbaceous  plants, 
with  leaves  alternate ;  flowers  apetalous, 
unisexual ;  ovarium  three-celled,  the  cells 
separating  with  elasticity  from  their  com- 
mon axis. 

EU'PHOTIDE.  A  rock  consisting 
essentially  of  felspar  and  diallage,  aggre- 
gated together  in  the  manner  of  granite. 
The  Italian  artists  call  it  gabbro. 

EUPION  (el,  well,  irtV,  fat).  A 
colourless  liquid,  obtained  by  distillation 
from  the  tar  of  animal  matters,  and  so 
named  from  its  great  limpidity. 

EUPY'RION  (el,  easily,  ™P,  fire). 
Any  contrivance  for  obtaining  an  instan- 
taneous light,  as  the  phosphorus  bottle. 

EURITE,  or  WHITESTONE.  A  va- 
riety of  granite,  in  which  felspar  is  the 
predominant  ingredient ;  or  in  which  all 
the  ingredients  are  blended  into  a  finely 
granular  mass  of  a  white  appearance. 

EVAPORATION.  1 .  Spontaneous  eva- 
poration is  the  production  of  vapour  by 
some  natural  agency,  without  the  direct 
application  of  heat,  as  on  the  surface  of 
the  earth  or  ocean.  This  is  commonly 
termed  exhalation.  2.  The  chemical  ope- 
ration is  usually  performed  by  applying 
heat  to  any  compound  substance,  in  order 
to  separate  the  volatile  parts,  which  are 
dissipated  and  lost.  In  this  respect,  eva- 
poration differs  from  distillation,  which 
chiefly  consists  in  preserving  the  volatile 
parts. 

EVE'CTION  (eveho,  to  raise  up).  A  term 
applied  to  certain  irregularities,  con- 
sisting of  elongations  or  contractions,  of 
the  moon's  orbit.  They  depend  upon  the 
varying  attraction  exercised  by  the  earth 
upon  the  moon,  according  as  the  latter  is 
in  apogee  or  perigee,  and  as  consequently 
more  or  less  under  the  influence  of  the 
sun's  attraction.  They  are  periodical, 
running  through  all  their  changes  in 
about  twenty-seven  days.  See  Angle  of 
Evection. 


EXC 


EXO 


EVERGREEN.  A  terra  applied  to 
plants  which  have  persistent  or  perennial 
leaves ;  i.  e.  leaves  which  remain  perfect 
upon  the  plant  beyond  a  single  season,  as 
holly,  common  laurel,  &c. 

EVERLASTING  FLOWERS.  A  po- 
pular designation  of  certain  flowers  which 
retain  their  colour  for  many  months  after 
they  have  been  gathered,  owing  to  the 
hardness  of  their  tissue,  and  the  small 
amount  of  moisture  which  they  con- 
tain. 

E'VOLUTE  (evolutus,  unrolled).  A 
curve  from  which  any  given  curve  may 
be  supposed  to  be  formed  by  the  evolu- 
tion or  unlapping  of  a  thread  from  a  sur- 
face having  the  same  curvature  as  the 
first  curve.     See  Curve. 

EVOLUTION  {evolvo,  to  roll  out).  A 
term  applied  to  a  theory  of  non-sexual 
generation,  according  to  which  the  first 
created  embryos  of  each  species  must 
contain  within  themselves,  as  it  were  in 
miniature,  all  the  individuals  of  that  spe- 
cies which  shall  ever  exist ;  and  must 
contain  them  so  arranged,  that  each  gene- 
ration should  include  not  only  the  next, 
but,  encased  within  it,  all  succeeding 
generations.  Hence  this  theory  has  also 
received  the  name  of  the  emboitement 
theory.    Compare  Epigenesis. 

EVOLUTION  (in  Algebra).  The  ex- 
traction of  roots,  or  the  method  of  find- 
ing a  quantity,  which,  raised  to  a  pro- 
posed power,  will  produce  a  given  quan- 
tity. It  is  just  the  reverse  of  in- 
volution ;  and  to  perform  the  operation, 
we  must  inquire  what  quantify  multi- 
plied into  itself,  till  the  number  of  fac- 
tors amounts  to  the  number  of  units  in 
the  index  of  the  given  root,  will  gene- 
rate the  quantity  whose  root  is  to  be  ex- 
tracted. 

EXCENTRICITY  (ef,  out,  Kevrpov, 
centre).  The  ratio  which  the  distance 
between  the  centre  and  focus  of  an  ellipse 
or  hyperbola  bears  to  the  whole  semi- 
axis.  Half  the  distance  between  the 
foci  of  an  ellipse  is  called  its  excen- 
tricity,  and  sometimes  its  ellipticity.  It 
is  in  this  way  that  we  speak  of  the  excen- 
tricity  of  the  orbits  of  the  planets  which 
are  supposed  to  move  in  ellipses  ;  the  cir- 
cle which  circumscribes  the  elliptic  orbit 
of  a  planet  being  called  the  excentric. 
Hence,  the  excentric  anomaly  is  the  arc 
of  the  excentric  between  the  perihelion 
of  the  orbit,  and  the  straight  line  drawn 
through  the  centre  of  the  planet  perpen- 
dicular to  the  major  axis.    See  Anomaly. 

EXCHANGES,  THEORY  OF.  A 
131 


theory  introduced  by  Prevost  for  explain- 
ing the  equilibrium  of  temperature  of 
any  body.  It  is  founded  on  the  suppo- 
sition that  the  quantity  of  heat  which 
the  body  diffuses  by  radiation,  is  equal  to 
that  which  it  receives  by  radiation  from 
surrounding  objects,  and  which  it  either 
wholly  or  in  part  absorbs. 

EXCFPULUS.  That  part  of  the  thallus 
which  forms  the  rim  and  base  of  the 
shields  of  lichens. 

EXCITATION  OF  ELECTRICITY. 
The  disturbance  of  the  electric  equili- 
brium by  friction,  elevation  of  tempe- 
rature, contact,  &c.  Bodies  have  been 
distinguished  into  conductors  and  non- 
conductors, according  to  the  facility  with 
which  the  electric  influence  passes,  or  is 
conducted,  along  their  surfaces. 

EXCITO-MOTORY.  A  designation  of 
that  function  of  the  nervous  system, 
discovered  by  Dr.  Marshall  Hall,  by 
which  an  impression  is  transmitted  to  a 
centre,  and  reflected  so  as  to  produce  con- 
traction of  a  muscle,  without  sensation 
or  volition. 

EXCU'RRENT  {excurro,  to  run  out). 
A  term  applied  to  that  mode  of  ramifica- 
tion in  plants,  in  which  the  axis  remains 
always  in  the  centre,  all  the  other  parts 
being  regularly  disposed  around  it,  as  in 
pinus  abies. 

EXCURTRI'CES  {excurro,  to  rush 
hastily).  Snatchers;  a  name  given  by 
Macgillivray  to  an  order  of  Birds,  inter- 
mediate between  the  flying  and  walking 
tribes,  and  belonging  to  the  Insessores  of 
other  writers.  They  include  the  shrikes 
and  fly-catchers,  the  thick-bills  and  the 
rollers. 

EXHALATION.  A  general  term  for 
all  the  effluvia  or  steams  raised  from  the 
surface  of  the  earth  in  form  of  vapour. 
Some  distinguish  exhalations  from  va- 
pours, expressing  by  the  former  all  steams 
emitted  from  solid  bodies,  and  by  the 
latter,  the  steams  raised  from  water  and 
other  fluids. 

EXI'NTINE.  A  term  applied  by 
Fritzsche  to  a  third  membrane  situated 
between  the  extine  and  the  intine,  in 
the  pollen  of  yew,  juniper,  cypress,  &c. 

EXO-  (efa>).  A  Greek  adverb,  signify- 
ing without,  on  the  outside,  &c. 

1.  Exo-genous  (jeivo/jiai,  to  be  pro- 
duced). Outside-growing ;  increasing  in 
diameter  by  deposition  to  the  exterior :  a 
term  applied  to  the  structure  of  the  axis 
of  dicotyledonous  plants,  in  which  the 
newest-formed  fibres  are  deposited  on 
the  exterior  of  those  previously  formed, 
G6 


EXP 


EXT 


exhibiting,  on  a  transverse    section,   a 
series  of  concentric  circles  or  zones. 

•2.  Exo-phyllous  {<pu\\ov,  a  leaf).  A 
term  applied  by  Dumortier  to  the  exo- 
rrhizous  embryo,  in  consequence  of  the 
cotyledons  being  always  naked,  i.  e.  not 
evolved  from  a  coleophyllum  or  leaf- 
sheath. 

3.  Exo-ptile  (tttIKov,  a  feather).  A 
term  applied  by  Lestiboudois  to  the  dico- 
tyledonous embryo,  in  consequence  of  its 
plumule  being  naked,  i.  e.  not  enclosed 
within  the  substance  of  the  cotyledons. 

4.  Exo-rrhizous  (pi£a,  a  root).  A  term 
expressive  of  the  mode  of  germination 
in  exogenous  plants,  in  which  the  radicle 
appears  at  once  on  the  surface  of  the 
radicular  extremity  of  the  cotyledons, 
and  consequently  has  no  coleophyllum  or 
sheath  at  its  base,  as  occurs  in  the  en- 
dorrhizous  germination. 

5.  Ex-osmose  (wtrjuor,  impulsion).  The 
property  by  which  a  rarer  fluid  passes 
through  membranous  substances  out  of  a 
cavity  into  a  vessel  containing  a  denser 
fluid.  i 

6.  Exo-stome  (aro/jLa,  a  mouth).  The 
foramen  or  orifice  of  the  outer  integu- 
ment, or  primine,  of  the  ovule  in  plants. 

7.  Exo-thecium  (d^nn,  a  case).  A  term 
applied  by  Purkinje  to  the  coat  of  the 
anther,  in  plants. 

EXOCHNATA  (efoxor,  prominent).  A 
designation  of  the  long-tailed  Crustacea, 
as  the  lobster  and  shrimp. 

EXOTE'RIC  (e£<oTep<K6?,  external). 
A  term  applied  to  those  disciples  of  Py- 
thagoras and  others,  who  were  not  yet 
initiated  into  their  highest  philosophy; 
as  distinguished  from  the  esoteric,  who 
were  scientifically  taught.  The  term 
"exoteric"  was  also  applied  to  those 
writings  which  were  in  a  more  popular 
form,  while  the  "  esoteric  "  writings  were 
of  a  more  scientific  and  exact  character. 

EXPANSIBILITY  (expando,  to  spread 
out).  That  property  of  a  body  by  which 
it  is  capable,  under  certain  circumstances, 
of  occupying  more  space  than  it  usually 
requires.  The  principal  agent  in  the  ex- 
pansion of  bodies  is  caloric. 

EXPERIMENTUM  CRUCIS.  A  cru- 
cial or  decisive  experiment  in  attempting 
to  interpret  the  laws  of  nature ;  so  called, 
after  Bacon's  manner,  from  the  crosses,  or 
way-posts,  used  to  point  out  roads,  be- 
cause they  determine  at  once  between 
two  or  more  possible  conclusions. 

EXPLOSION.    The  sudden  and  vio- 
lent expansion  of  the  constituent  parts  of 
a  body. 
132 


EXPO'NENT  (expono,  to  explain).  A 
small  figure,  or  other  symbol,  placed  at 
the  right  hand  of  an  algebraical  quantity, 
to  express  its  power.  It  is  equivalent  to 
the  number  of  factors,  and  is  also  called 
the  index  of  the  power.  Thus,  in  the 
expression  a2,  the  figure  2  is  the  index 
or  exponent,  and  denotes  that  the  quan- 
tity is  the  square  of  a. 

1.  Exponent  of  a  rank.  The  number 
or  place  of  any  term  in  a  series  :  thus,  in 
the  series  1,  3,  5,  7,  9,  11,  13,  15,  &c,  7  is 
the  exponent  of  the  rank  of  13,  this  term 
being  the  7th  in  the  order  of  the  series. 

2.  Exponent  of  a  geometrical  ratio. 
The  quotient  which  arises  from  dividing 
the  consequent  by  the  antecedent  of  the 
ratio.  Thus,  in  the  ratio  of  2  to  8,  the 
exponent  is  §  =  4;  and,  in  the  ratio  of 
8  to  2,  the  exponent  is  |  =  £.  Some  ma- 
thematicians, however,  consider  loga- 
rithms as  the  exponents  of  ratios. 

EXPONENTIAL.  This  term  is  va- 
riously applied.  The  exponential  calculus 
is  that  part  of  Algebra  which  relates  to 
exponential  quantities,  or  quantities  raised 
to  powers  of  which  the  exponents  are  in- 
determinate or  variable.  An  exponential 
curve  is  a  curve  defined  by  an  exponential 
equation,  or  an  equation  which  contains 
an  exponential  quantity.  Exponential 
equations  are  commonly  resolved  by 
means  of  logarithms. 

EXSERTED  {exsertus,  thrust  out).  A 
term  applied  to  the  stamens  of  plants, 
when  they  are  longer  than  the  corolla. 

EXSICCATION  {exsicco,  to  dry  up). 
A  variety  of  evaporation,  producing  the 
expulsion  of  moisture  from  solid  bodies 
by  heat,  and  generally  employed  for  de- 
priving salts  of  their  water  of  crystalliza- 
tion. 

EXTENSION  (extendo,  to  stretch  out). 
That  property  of  matter  by  which  it  occu- 
pies space :  it  relates  to  the  qualities  of 
length,  breadth,  and  thickness,  without 
which  no  substance  can  exist ;  but  has 
no  respect  to  the  size  or  shape  of  a  body. 
This  property  is  termed,  in  common  lan- 
guage, size  or  volume. 

EXTINE  {extimus,  outermost).  The 
outermost  membrane  of  the  pollen-grain 
in  plants. 

EXTRA'CTION  OF  ROOTS.  The 
arithmetical  or  algebraical  operation  of 
finding  the  root  of  a  number  or  quantity ; 
in  other  words,  the  finding  that  number 
or  quantity  which,  multiplied  into  itself 
a  certain  number  of  times,  will  produce 
the  given  number  or  quantity.  See  Evo- 
lution. 


FAC 


FAL 


EXTREME  AND  MEAN  RATIO. 
A  straight  line  is  said  to  be  divided  in 
extreme  and  mean  ratio,  when  the  whole 
is  to  the  greater  part  as  the  greater  part 
to  the  less ;  or  when  the  rectangle  con- 
tained by  the  whole  line  and  the  smaller 
segment  is  equal  to  the  square  of  the 
greater  segment. 

EXTRE'MES  (extremus,  last).  In 
Logic,  the  subject  and  predicate  of  a  pro- 
position are  called  its  extremes  or  terms, 
being,  as  it  were,  the  two  boundaries, 
having  the  copula  (in  regular  order) 
placed  between  them.  In  speaking  of  a 
syllogism,  the  word  is  often  understood 
to  imply  the  extremes  of  the  conclusion. 

EXTRORSE  (extrorsum,  towards  the 
outside).  Turned  outwards  ;  turned  away 
from  the  axis  to  which  it  belongs;    a 


term  applied,  in  botany,  to  those  anthers, 
whose  line  of  dehiscence  is  towards  the 
petals.  Brown  uses  the  term  posticce  in 
this  sense. 

EXU'VIiE  {exuo,  to  put  off).  The 
slough,  or  cast-off  covering  of  certain 
animals,  as  the  skins  of  the  serpent  and 
the  caterpillar.  This  term  relates,  how- 
ever, in  geological  language,  not  only  to 
the  rejected  envelopes  of  animals,  but  to 
fossil  shells  and  other  remains  which 
have  been  left  by  animals  in  the  strata  of 
the  earth. 

EXUVIATION  (exuviez,  a  slough,  the 
cast-off  skin  of  certain  animals).  A  term 
applied,  in  Zoology,  to  the  process  by 
which  the  crustaceous  animals  throw  off 
their  old  shell,  and  form  a  new  one. 


F 


FA'CET.  A  term  derived  from  the 
French,  denoting  a  flat  surface,  with  a 
definite  boundary.  The  English  term 
face  has  the  same  meaning  in  Geometry, 
and  is  applied  to  the  plane  which  forms 
one  of  the  surfaces  of  a  polyhedron. 

FACIAL  ANGLE.  This  angle  is  mea- 
sured by  drawing  a  line  from  the  pro- 
minent centre  of  the  forehead  to  the  most 
advanced  part  of  the  lower  jaw-bone,  and 
observing  the  angle  which  it  makes  with 
the  horizontal  line.  By  measurement  of 
this  angle  it  has  been  affirmed  that  a 
scale  might  be  traced  from  "apes  with 
foreheads  villainous  low  "  to  the  African 
variety  of  the  human  species,  and  from 
that  to  the  European. 

FACTITIOUS  {factito,  to  practise). 
Made  by  art,  as  factitious  cinnabar,  in 
distinction  from  the  natural  production. 
This  term  is  also  applied  to  waters  pre- 
pared in  imitation  of  natural  waters,  as 
those  of  Brighton. 

FA'CTOR.  A  term  applied  in  Algebra 
to  each  of  the  quantities  which  are  mul- 
tiplied into  one  another  in  order  to  form 
( facer e)  a  product,  i.  e.,  to  the  multiplier 
and  the  multiplicand  ;  thus  a  and  a  +  x 
are  the  factors  of  the  product  a  {a  +  x), 
or  a2  +  ax  Factors  are  also  called  divi- 
sors, especially  in  speaking  of  a  number, 
which  is  regarded  as  the  product  of  seve- 
ral others. 

Factorial  expression.  A  term  some- 
times applied  to  an  expression  of  which 
133 


the  factors  are  in  arithmetical  progression, 
as — 

(x+  1)  (*  +  2)  (x  +  3)  (x  +  4). 

FA'CULA  (dim.  of  fax,  a  torch).  A 
little  torch.  The  term  faculce  is  applied 
to  certain  luminous  spots  on  the  surface 
of  the  sun ;  they  are  of  irregular  form, 
of  variable  duration,  and  are  commonly 
surrounded  by  a  penumbra.  By  such 
spots  the  diurnal  revolutions  of  the 
planets,  as  well  as  that  of  the  sun,  have 
been  determined. 

FAHLERZE.  Fahlore.  A  grey  copper 
ore,  comprising  the  arsenical  and  the 
antimonial  varieties.  In  this,  and  in  seve- 
ral other  double  sulphurets  of  silver  and 
other  metals,  the  sulphuret  of  silver  and 
the  sub-sulphuret  of  copper,  being  iso- 
morphous,  replace  each  other  in  inde- 
terminate proportions. 

FA'HLUNITE.  Automalite.  A  sub- 
species of  octohedral  corundum,  found  in 
a  talcose  rock,  at  Fahlun  in  Sweden. 

FA'LCATE  (falx,  a  scythe  or  sickle). 
Sickle- shaped ;  any  thing  plane  and 
curved,  with  parallel  edges.  The  moon 
is  said  to  be  falcate,  when  the  enlight- 
ened part  appears  in  the  form  of  a  cres- 
cent. In  Zoology,  a  part  is  said  to  be 
falcate,  when  it  is  curved  with  the  apex 
acute. 

FALCO'NID.E.  The  Falcon  tribe  ;  a 
family  of  the  Raptores,  or  Rapacious 
birds,  distinguished  from  the  Vultures  by 
their  shorter,  sharper,  and  notched  bill. 


F  AL 


FAU 


and  by  the  sharpness  and  curvature  of 
their  retractile  talons.  The  falcons  have 
been  divided  into  the  noble,  ox  falcons 
proper,  capable  of  being  trained  to  the 
sport  of  falconry,  and  the  ignoble,  which 
are  incapable  of  this  training.  This 
family  includes  the  eagle,  the  hawk,  the 
kite,  the  osprey,  &c. 

FA'LLACY  (fallacia,  deceit).  In 
Logic,  •'  an  unsound  mode  of  arguing, 
which  appears  to  demand  our  conviction, 
and  to  be  decisive  of  the  question  in 
hand,  when  in  fairness  it  is  not."  Falla- 
cies are  of  two  kinds : — 

1.  Logical  Fallacies,  or  fallacies  "in 
dictione,"  in  which  the  fault  is  in  the 
reasoning,  and  in  that  alone,  the  conclu- 
sion not  following  from  the  premises  ;  as 
in  the  indistributed  middle,  illicit  pro- 
cess, negative  premises,  or  affirmative 
conclusion  form  a  negative  premiss,  and 
vice  versd. 

2.  Non-logical  fallacies,  or  fallacies 
"  extra  dictionem,"  in  which  the  fault  is 
in  the  matter.  Of  these  there  are  two 
kinds ;  viz.  1st,  when  the  premises  are 
such  as  ought  not  to  have  been  assumed ; 
2nd,  when  the  conclusion  is  not  the  one 
required,  but  irrelevant.  To  this  head 
belong  the  fallacies  of  "non  causa  pro 
causa,"  "  petitio  principii,"  &c. 

FALSE.  This  term,  in  its  strict  logi- 
cal sense,  denotes  the  quality  of  a  pro- 
position which  states  something  not  as  it 
is.  Logicians  express  this  quality  of  a 
proposition  by  the  word  falsity,  as  being 
more  precise  than  the  word  falsehood, 
which  is  opposed  not  merely  to  logical, 
but  also  to  moral  truth. 

FALSE  CADENCE.  In  Music,  a 
cadence  in  which  the  base  rises  a  tone  or 
semitone,  instead  of  rising  a  fourth  or 
falling  a  fifth. 

FALSE  POSITION.  A  rule  in  arith- 
metic, according  to  which,  by  false  or 
supposed  numbers,  taken  at  pleasure,  the 
true  required  number  is  discovered. 
There  are  two  methods :  by  single  posi- 
tion, one  supposed  number  is  used,  and, 
by  working  with  this  as  the  true  one,  the 
real  number  required  is  found ;  by  double 
position,  two  supposed  numbers  are  used, 
and  if  both  prove  false  (as  it  generally 
happens),  they  are  subjected  to  further 
arithmetical  investigation. 

FALSE'TTO.  An  Italian  term,  ap- 
plied in  Music  to  a  false  or  artificial 
voice,  by  which  the  vocal  compass  is  ex- 
tended, by  contracting  the  aperture  of 
the  throat,  several  notes  above  the  natu- 
ral voice.  The  Italians  call  the  falsetto 
134 


voce  di  testa,  or  voice  from  the  head  ;  the 
natural  voice,  voce  di  petto,  or  voice  from 
the  chest. 

FALUNS.  A  French  provincial  name 
for  some  tertiary  strata,  abounding  in 
shells,  in  Touraine,  which  resemble  in 
lithological  characters  the  "Crag"  of 
Norfolk  and  Suffolk. 

FAMILY.  In  classifications  of  Zoology, 
Botany,  &c,  this  term  denotes  the  group 
next  in  value  and  comprehensiveness 
above  the  genus.  As  species  constitute 
a  genus,  so  genera  constitute  a  family,  or 
order. 

FARI'NA  (far,  f arris,  corn).  Meal, 
or  vegetable  flour,  made  from  the  seed 
of  the  Winter  Wheat.     See  Amylum. 

Farinaceous.  A  term  for  all  those  sub- 
stances which  contain  farina;  viz.  the 
cerealia,  legumes,  &c. 

FA'SCLE  (fascia,  a  band).  Stripes  or 
belts  observed  on  the  disc  of  Jupiter  and 
other  planets.  In  Botany,  contiguous 
stems  or  fruits,  which  have  grown  unna- 
turally together,  are  said  to  be  fasciated. 

FA'SCICLE  (fasciculus,  a  little  bundle). 
A  form  of  inflorescence  resembling  a 
corymb,  but  having  a  centrifugal,  instead 
of  a  centripetal,  expansion.  It  is  a  kind 
of  compound  corymb. 

FASCFCULATE  (fasciculus,  a  little 
bundle).  Clustered ;  as  when  several 
bodies  spring  from  a  common  point,  as 
the  leaves  of  larix,  the  tubers  of  orchis, 
the  roots  of  commelina,  &c. 

FASTI'GIATE  (fastigium,  the  top  of 
any  thing).  A  term  used  in  Botany  to 
denote  that  the  branches  of  a  tree  are 
appressed  to  the  stem,  assuming  nearly 
the  same  direction,  as  in  populus  fasti- 
giata. 

FA'TA  MORGANA.  Castles  of  the 
Fairy  Morgana.  A  meteorological  phe- 
nomenon occasionally  witnessed  in  the 
Straits  of  Messina,  and  depending  on 
unusual  refraction.  The  images  of  men, 
of  buildings,  and  other  objects  are  seen 
from  the  coast,  sometimes  in  the  water, 
sometimes  at  the  surface  of  the  water,  or 
in  the  air  :  there  may  be  two  images  of 
the  same  object,  the  one  in  a  natural,  the 
other  in  an  inverted  position ;  or  the 
images  of  the  same  object  may  be  mul- 
tiplied to  a  great  degree. 

FAULT.  A  technical  term  applied  by 
miners  to  a  sudden  interruption  of  the 
continuity  of  strata  in  the  same  place, 
accompanied  by  a  crack  or  fissure,  vary- 
ing in  width  from  a  mere  line  to  several 
feet,  which  is  generally  filled  with  broken 
stone,  clay,  and  other  materials.    The 


FEL 


FER 


displacement  of  the  strata  is  owing  to 
the  upheaving  on  the  one  side,  or  to  sub- 
sidence on  the  other  side,  of  the  fault. 

FAUNA  (Fauni,  the  rural  divinities). 
A  term  denoting  the  animals  peculiar  to 
any  particular  country. 

FAUX.  The  throat ;  the  orifice  of  the 
tube  of  a  gamopetalous  corolla. 

FAVOSE  {favus,  a  honey-comb).  Ho- 
ney-combed ;  excavated  like  a  honey- 
comb, as  the  receptacle  of  onopordum, 
the  seeds  of  poppy,  &c. 

FE'CULA  (fcex,  the  grounds  or  settle- 
ment of  any  liquor).  Originally,  any  sub- 
stance derived  by  spontaneous  subsidence 
from  a  liquid ;  the  term  was  afterwards 
applied  to  starch,  which  was  thus  depo- 
sited by  agitating  the  flour  of  wheat  in 
water ;  and  lastly,  it  denoted  a  peculiar 
vegetable  principle,  which,  like  starch,  is 
insoluble  in  cold,  but  completely  soluble 
in  boiling  water,  with  which  it  forms  a 
gelatinous  solution. 

FECUNDATION  (fecundo,  to  make 
fruitful).  Impregnation.  The  effect  of 
the  vivifying  fluid  upon  the  germ  or 
ovum,  which  is  then  called  the  embryo. 

FE'LIDjE  {felis,  a  cat).  The  Cat  tribe ; 
a  family  of  carnivorous  Vertebrata,  cha- 
racterized by  their  short  powerful  jaws, 
retractile  claws,  and  the  peculiar  adapt- 
ation of  their  teeth  for  cutting.  They 
are,  among  the  quadrupeds,  what  the 
Falconidce  are  among  Birds. 

FELLOWSHIP.  A  rule  in  arithmetic, 
by  which  profit  or  loss  is  divided  between 
two  or  more  partners,  in  proportion  to 
the  principal  of  each  in  joint  stock.  The 
rule  is  applicable  to  cases  in  which  the 
investments  are  made  for  the  same  time, 
and  to  cases  in  which  the  partners  em- 
ployed their  principal  at  different  times  : 
the  former  belong  to  the  rule  of  fellow- 
ship without  time ;  the  latter,  to  that  of 
fellowship  with  time. 

FE'LSPAR.  A  simple  mineral  which, 
next  to  quartz,  constitutes  the  chief  ma- 
terial of  rocks.  The  white  angular  por- 
tions of  granite  consist  of  felspar.  This 
mineral  always  contains  some  alkali  in 
its  composition:  in  common  felspar  the 
alkali  is  potash;  in  the  variety  called 
Albite  or  Cleavlandite,  it  is  soda.  The 
term  glassy  felspar  denotes  that  the  crys- 
tals have  a  high  degree  of  transparency. 
Compact  felspar  appears  to  contain  both 
potash  and  soda.     See  Adularia. 

Felspar-porphyry.    A  felspathic  rock, 
in  which  crystals  of  felspar  are  mixed 
with  hornblende,  mica,  or  quartz. 
FELSPA'THIC    ROCKS.     Rocks   of 
135 


which  felspar  is  the  chief  constituent, 
comprising  granite,  gneiss,  claystone, 
lava,  and  other  varieties. 

FENE'STRATE  (fenestra,  a  window). 
Windowed ;  a  term  applied  to  the  incom- 
plete dissepiment  sometimes  occurring 
in  the  siliqua  of  cruciferous  plants. 

FE'RGUSONITE.  A  crystallized  min- 
eral, occurring  principally  as  a  columbate 
of  yttria.  It  has  been  found  only  in 
Greenland,  near  Cape  Farewell,  imbedded 
in  quartz. 

FE'RMENT  (fermentum,  quasi  fervi- 
mentum,  from  ferveo,  to  work).  A  sub- 
stance which  possesses  the  power  of 
commencing  fermentation.  It  is  either 
naturally  present,  as  in  the  grape,  or  is 
added,  as  in  the  case  of  yeast. 

FERMENTATION.  Certain  changes 
of  animal  or  vegetable  substances,  re 
duced  to  the  moist  or  liquid  state  by 
water.     There  are  several  kinds : — 

1.  The  Saccharine ;  when  the  change 
terminates  in  sugar,  as  that  of  starch. 
/  The  Panary  ;    as    that  of      flour 

„    j      forming  bread  :— or 

j  The  Vinous ;  as  that  of  the  grape, 
^     &c,  forming  wine; — 
evolving  alcohol. 

3.  The  Acetous;  when  the  result  is 
acetic  acid,  or  vinegar. 

4.  The  Putrefactive ;  generally  of  ani- 
mal substances,  evolving  ammonia. 

5.  The  Lactic;  when  no  alcohol  is 
evolved,  but  the  liquid  becomes  mucila- 
ginous and  thick,  with  the  production  of 
mannite  and  lactic  acid. 

FE'RRIC  OXIDE  (ferrum,  iron).  Per- 
oxide of  iron  ;  a  mineral  occurring  abun- 
dantly in  nature,  as  oligistic  or  specular 
iron,  forming  the  celebrated  Elba  ore ;  as 
red  hematite,  which  is  cut,  and  forms  the 
burnishers  of  bloodstone  ;  and  in  combi- 
nation with  water,  as  brown  hematite, 
employed  in  most  of  the  iron  furnaces  of 
France. 

1.  Ferroso  -ferric  Oxide.  The  black 
oxide,  magnetic  oxide  of  iron,  or  martial 
ethiops.  It  occurs  in  the  mineral  king- 
dom, under  the  name  of  magnetic  iron- 
ore,  the  massive  form  of  which  is  called 
native  loadstone. 

2.  Ferroso-ferric  Sulphate.  The  name 
given  by  Berzelius  to  a  combination  of 
the  proto-  and  per-sulphates  of  iron. 

FERRI'FEROUS  ROCKS  (ferrum, 
iron,  fero,  to  bear).  Rocks  in  which  iron- 
ore  is  abundantly  distributed,  comprising 
clay  iron-ore  and  iron  pyrites. 

FERROCYA'NIC  ACID.  Ferrocya- 
nide  of  Hydrogen.  A  compound  of  cyano- 


FI  F 

gen,  metallic  iron,  and  hydrogen ;  also 
called  ferruretted  chyazic  acid.  It  con- 
tains the  elements  of  hydro-cyanic  acid, 
hut  differs  from  it  totally  In  its  properties. 
Its  salts,  formerly  called  triple  prussiates, 
are  now  termed  ferro-cyanides.  The 
beautiful  pigment  Prussian  blue  is  a 
ferro-cyanide  of  the  peroxide  of  iron. 

FERRU'GINOUS  (ferrugo,  quasi  ferri 
cemgn,  rust  of  iron).  Containing  iron, 
or  of  the  nature  of  iron,  as  certain  salts, 
mineral  waters,  &c.  The  term  ferrugo 
is  applied,  in  Botany,  to  a  disease  of 
plants,  commonly  called  rust,  and  occa- 
sioned by  the  presence  of  minute  fungi, 
chiefly  of  the  genus  uredo. 

FERTILIZATION  (fertilis,  fertile). 
The  function  of  the  pollen  of  plants  upon 
the  pistil,  by  means  of  which  the  ovules 
are  converted  into  seeds. 

FETTSTEIN  (German,  fat  stone).  A 
designation  of  a  sub-species  of  pyramidal 
felspar,  from  its  resinous  nature.  The 
term  is  synonymous  with  elaolite,  which 
means  oil-stone. 

FIBRE  (fibra,  a  filament).  A  filament 
of  thread,  of  animal,  vegetable,  or  mineral 
composition.  A  fibril  is  a  minute  sub- 
division of  a  fibrous  root. 

FI'BRIN  (fibra,  a  fibre).  A  principle 
found  in  vegetables  as  a  constituent  of 
gluten ;  and  in  the  living  blood  of  ani- 
mals, constituting  muscular  fibre. 

FI'BROLITE.  A  mineral  of  a  pecu- 
liar fibrous  texture,  found  in  the  Car- 
natic,  and  consisting  of  alumina,  silica, 
and  iron. 

FIBROUS  (fibra,  a  fibre  or  thread). 
Consisting  of  or  resembling  fibres ;  as 
indicating  the  structure  of  a  shell  when 
fractured. 

FI'BROUS  COAL.  A  variety  of 
glance-coal,  distinguished  by  its  fibrous 
concretions  and  silky  lustre.  It  occurs 
in  the  coal-fields  of  Great  Britain. 

FIELD  OF  VISION.  A  technical 
expression  for  the  space  or  range  seen 
through  a  telescope.  It  is  measured  by 
dividing  the  angle  under  which  it  is  seen 
by  the  angle  of  vision  of  the  naked  eye 
embracing  the  same  field  within  its  view. 
The  greater  the  magnifying  power  of  the 
instrument,  the  less  will  be  the  angle  of 
vision  of  the  naked  eye,  compared  with 
that  of  an  eye  looking  through  the 
glass. 

FIFTH.  An  interval  in  Music,  occur- 
ring in  the  natural  scale,  in  the  fifth 
place  from  the  fundamental.  The  false 
fifth  is  less  than  the  fifth  by  a  lesser 
semitone. 
136 


FIG 

FIFTEENTH.  In  Music,  an  interval 
of  two  octaves.  The  fifteenth  stop  in 
organs  is  a  double  octave  above  the  dia- 
pason. 

FI'GURATE  NUMBERS.  Certain 
series  of  numbers  deduced  from  any  pro- 
gression, by  taking  the  sum  of  the  first 
two,  the  first  three,  the  first  four,  &c, 
terms  of  the  progression,  and  then  ope- 
rating on  the  series  thus  obtained,  in 
order  to  obtain  a  new  series,  and  so  on. 
For  example  : — 

A 1,  2,    3,    4,    5,      6,      7, 

B 1,  3,    6,  10,  15,    21,    28, 

C 1,  4,  10,  20,  35,    56,    84, 

D 1,  5,  15,  35,  70,  126,  210. 

1.  The  series  A  is  the  arithmetical 
progression  from  which  the  other  series 
are  deduced.  The  series  B  consists  of 
triangular  or  polygonal  numbers  of  the 
preceding  progression,  so  named  from 
certain  analogies  which  the  numbers  so 
denoted  have  with  the  geometrical  figures 
bearing  the  same  denominations.  The 
series  C  consists  of  triangular  pyramidal 
numbers,  and  is  formed  from  the  pre- 
ceding series  in  the  same  way  as  this 
from  the  original  progression.  The  series 
D  consists  of  second  pyramidals,  and  is 
formed  like  the  preceding  series. 

2.  If  the  common  difference  of  the  first 
progression  were  2,  the  successive  series 
would  consist  of  square  numbers ;  if  the 
common  difference  were  3,  the  series 
would  be  pentagonal  numbers ;  if  4, 
hexagonal  numbers,  and  so  on;  the  num- 
bers thus  obtained  being  capable  of  being 
placed  in  the  form  of  squares,  pentagons, 
hexagons,  &c. 

FIGURE.  Figure,  or  form,  is  a  pro- 
perty of  bodies,  resulting  from  extension. 
The  volume  of  a  body  has  no  relation  to 
its  figure:  bodies  which  have  the  same 
figures  may  possess  very  different  vo- 
lumes; and  bodies  may  have  the  same 
volume  under  very  different  figures; 
thus,  two  masses  of  matter  may  present 
the  same  volume,  although  the  one  be 
round  and  the  other  square. 

FIGURE  (in  Geometry).  A  finite 
space,  bounded  on  all  sides  by  lines  or  by 
planes.  The  term  is  also  employed  as 
synonymous  with  diagram. 

FIGURE,  APPARENT.  A  term  in 
Optics,  denoting  the  figure  under  which 
an  object  presents  itself  to  the  eye.  As 
this  depends  on  the  situation  of  the 
points  from  which  the  rays  of  light  pass 
to  the  eye,  the  apparent  figure  may  be 
very  different  from  the  real  figure  of  an 
object ;  a  straight  line,  for  instance,  may 


FIR 


FLA 


appear  as  a  point,  a  plane  as  a  straight 
line,  and  a  solid  as  a  simple  surface. 

FIGURE  OF  A  SYLLOGISM.  A 
logical  expression,  denoting  the  situation 
of  the  middle  term  with  respect  to  the 
extremes  of  the  conclusion  (i.  e.  the 
major  and  the  minor  term).  The  figures 
of  reasoning  are  only  different  forms  of 
stating  it. 

FI'LAMENT  (filamentum,  a  little 
thread).  The  thread-like  portion  of  the 
stamen,  which  supports  the  anther. 

FI'LICES  (filix,  a  fern).  The  Fern 
tribe  of  Acotyledonous  plants.  Leafy 
plants,  producing  a  rhizome;  fronds 
simple  or  variously  divided;  flowerless; 
reproductive  organs  consisting  of  thecce 
or  semi-transparent  cases  appearing  on 
the  back  or  margin  of  the  fronds. 

FILITE'L^  (filum,  a  thread,  tela,  a 
web).  A  family  of  Spiders,  remarkable 
for  the  long  threads  of  silk  which  they 
spread  about  in  the  places  where  they 
prowl  in  quest  of  prey. 

FILTRATION.  The  process  of  strain- 
ing a  liquid  through  a.  filter,  or  separating 
it  mechanically  from  the  particles  which 
are  mixed  with  it.  Filters  are  usually 
made  of  unsized  or  blotting  paper. 

FI'MBRIATED  (fimbria,  a  fringe). 
Fringed ;  having  the  margin  bordered  by 
filiform  appendages;  a  term  applied  to 
the  thin,  elevated,  fin-like  processes, 
belonging  to  many  of  the  murices,  and 
sometimes  placed  round  the  aperture  of 
cyclostomous  land-shells. 

FI'ORITE.  Pearl  sinter;  a  volcanic 
production,  chiefly  silica,  in  a  stalactitic 
form. 

FIRE-BALLS.  Bolides,  or  fiery  me- 
teors ;  luminous  bodies,  which  suddenly 
appear  at  a  considerable  height  in  the 
atmosphere,  and  shoot  through  the 
heavens  with  great  velocity,  sometimes 
accompanied  with  the  fall  of  an  aerolite. 

FIRE  DAMP.  A  gas  evolved  in  coal 
mines,  consisting  almost  entirely  of  light 
carburetted  hydrogen. 

FIRE  ENGINE.  The  fire  engine  is  a 
modification  of  the  forcing  pump.  It 
consists  of  two  such  pumps,  the  pistons 
of  which  are  moved  by  a  lever  with  equal 
arms,  having  a  common  fulcrum.  When 
one  piston  is  descending,  the  other  is 
ascending-  The  machine  acts  precisely 
like  the  forcing  pump,  only  that  its 
power  is  doubled  by  having  two  pistons 
instead  of  one. 

FIRE,  GREEK.  An  inflammable 
composition  employed  in  the  wars  of  the 
middle  ages,  supposed  to  consist  princi- 
137 


pally  of  naphtha  mingled  with  pitch  and 
sulphur. 

FISH.  The  name  applied  to  a  class 
of  animals  occupying  the  lowest  station 
of  the  four  great  divisions  of  the  section 
Vertebrata.  They  are  distinguished, 
with  reference  to  the  substance  of  their 
skeleton,  into  the  osseous  and  the  carti- 
laginous or  chondropterygious.  See 
Ichthyology. 

FISSI'PAROUS  (fissus,  cleft,  pario, 
to  bring  forth).  A  designation  of  that 
mode  of  propagation,  which  takes  place 
by  spontaneous  division  of  the  body  of 
the  parent  into  two  or  more  parts,  each 
part,  when  separated,  becoming  a  dis- 
tinct individual,  as  in  the  monad,  vorti- 
cella,  &c. ;  or  by  artificial  division,  as  in 
the  hydra,  planaria,  &c. ;  and  in  the 
propagation  of  plants  by  slips. 

FISSIPE'NN^E  (fissus,  cleft,  penna, 
a  wing).  A  family  of  Lepidopterous  in- 
sects, commonly  called  Plumed  Moths, 
and  characterized  by  the  division  of  the 
membrane  of  the  wings  into  branches  or 
rays,  of  which  each  pair  has  from  two  to 
six. 

FISSIRO'STRES  (fissus,  cleft,  ros- 
trum, a  bill).  A  group  of  the  Insessores, 
or  Perching  Birds,  having  a  short,  broad, 
horizontally-depressed  bill,  so  formed 
that  the  gape  of  the  mouth  is  extremely 
wide.  It  comprises  the  swallows,  goat- 
suckers, bee-eaters,  kingfishers,  and 
todies. 

FISTULOUS  (fistula,  a  pipe).  Cylin- 
drical and  hollow,  as  the  stems  of  grasses, 
of  umbelliferous  plants,  &c. 

FIXED  AIR.  A  name  formerly  given 
by  chemists  to  the  air  which  was  extri- 
cated from  lime,  magnesia,  and  alkalies, 
now  called  carbonic  acid  gas. 

FIXED  SIGNS  OF  THE  ZODIAC. 
These  are  Taurus,  Leo,  Scorpio,  and 
Aquarius ;  they  are  so  called  because 
the  season  is  considered  to  be  more 
settled  when  the  sun  passes  through 
these  signs,  than  at  any  other  times  of 
the  year. 

FIXED  STARS.  Stars  which  do  not 
appear  to  change  their  relative  situations, 
as  distinguished  from  planets  and  comets. 

FI'XITY.  The  property  by  which 
bodies  resist  the  action  of  heat,  so  as  not 
to  rise  in  vapour,  as  the  fixed,  in  contra- 
distinction to  the  volatile  oils ;  or  non- 
metallic  elements,  which  can  neither  be 
fused  nor  volatilized,  as  carbon,  silicon, 
and  boron. 

FLABE'LLIFORM  (fiabellum,  a  fan, 
forma,  likeness).     Fan-shaped  ;   plaited 


FLI 


FLO 


likethe  rays  of  a  fan,  as  descriptive  of 
the  leaves  of  some  palms. 

FLAGE'LLUM  (Lat.  a  whip).  An 
appendage  of  the  legs  of  the  Crustacea, 
resembling  a  whip.  By  the  early  bota- 
nists the  term  flagella  was  applied  to  the 
trailing  shoots  of  the  vine  ;  and  the  word 
flagelliform,  or  whip-like,  is  employed  to 
characterize  the  long,  taper,  and  supple 
roots  of  certain  plants. 

FLAKE-WHITE.  Oxide  of  bismuth, 
so  called  from  its  occurring  in  the  form 
of  small  laminae  or  flakes.  The  term  is 
often  applied  to  the  purest  white  lead. 

FLAME.  Gaseous  matter  heated  so 
highly  as  to  become  luminous.  The 
flame  of  volatile  carbonaceous  combus- 
tibles, as  coal  gas,  consists  of  three  parts 
— an  interior  cone  of  vaporized  combus- 
tible, an  intermediate  sphere  of  partial 
combustion,  and  an  exterior  sphere  of 
complete  combustion. 

FLAMELESS  LAMP.  A  lamp  in 
which  the  combustion  of  inflammable 
substances  is  carried  on  at  a  temperature 
below  that  required  for  their  inflamma- 
tion. Thus,  if  a  jet  of  the  gaseous  hydro- 
carbons be  allowed  to  escape  into  the  air, 
and  a  red-hot  coil  of  platinum  be  intro- 
duced into  it,  the  wire  will  be  maintained 
at  a  red  heat,  and  the  gas  will  be  con- 
sumed invisibly ;  but  if  the  temperature 
of  the  wire  be  raised  to  a  white  heat, 
the  gas  will  immediately  burst  into 
flame. 

FLAT.  A  character  in  Music,  marked 
(?,  which  depresses  the  note  before  which 
it  is  placed  a  chromatic  semitone.  An 
accidental  flat  is  that  which,  not  occur- 
ring in  the  clef,  affects  only  the  bar  in 
which  it  is  placed.  A  double  flat  de- 
presses a  note  two  semitones  below  its 
natural  state ;  thus  B  double  flat  is,  in 
fact,  A  natural.  A  flat  fifth  is  an  inter- 
val of  a  fifth  depressed  by  a  flat,  called 
by  the  ancients  semidiapente. 

FLEXIBILITY  (flecto,  to  bend).  That 
property  of  bodies  by  which,  on  the  ap- 
plication of  force,  they  change  their  form 
and  bend ;  it  is  opposed  to  stiffness  on 
the  one  hand,  and  to  brittleness  on  the 
other. 

FLE'XURE  (flecto,  to  bend).  The 
bending  of  a  line  or  surface.  The  point 
of  contrary  flexure  is  that  point  of  a 
curve  at  which  the  curvature  passes 
from  convex  to  concave,  or  vice  versa, 
with  respect  to  the  axis. 

FLINT.  Silex.  A  mineral,  consisting 
of  silicious  earth,  nearly  pure.  In  Geo- 
logy* flint  is  a  variety  of  the  quartzose 
138 


rocks,  of  various  colours,  with  a  con- 
choidal  fracture  and  horny  aspect.  Flinty 
slate,  silicious  schistus,  or  Lydian  stone, 
is  another  variety  of  the  same  rocks, 
and,  when  polished,  is  used  as  a  touch- 
stone for  ascertaining  the  comparative 
purity  of  gold  and  silver. 

FLINTS,  LIQUOR  OF.  A  solution 
of  flint  or  silica  in  potash,  prepared  by 
fusing  together  hydrate  of  potash  and 
powdered  flint  or  fine  sand. 

FLOATATION,  STABLE.  A  term 
applied  to  that  position  of  a  floating  body 
in  which  it  is  not  capable  of  being  upset 
by  the  exertion  of  a  small  force,  but  in- 
variably returns  to  its  former  position. 
This  is  not  the  case  when  its  position  is 
unstable,  as  small  impulses  then  induce 
a  change  of  place,  which  commonly  pro- 
duces stable  equilibrium. 

FLOATING  CURRENT.  A  move- 
able conductor,  invented  by  De  la  Rive, 
for  illustrating  the  action  of  electric  cur- 
rents on  each  other. 

FLOATSTONE.  A  sub-species  of  the 
indivisible  quartz  of  Mohs.  It  occurs 
incrusting  flint,  or  in  imbedded  masses 
in  a  secondary  limestone  at  St.  Ouen, 
near  Paris. 

FLOCCI  (floccus,  a  lock  of  wool). 
Woolly  filaments  found  mixed  with  spo- 
rules  in  the  interior  of  some  fungaceous 
plants.  The  same  name  is  also  applied 
to  the  external  filaments  of  Byssaceae. 

FLOETZ  ROCKS  (flotz,  German,  a 
layer  or  stratum).  A  term  applied,  in 
Germany,  to  the  secondary  strata,  because 
these  rocks  were  supposed  to  occur  most 
commonly  in  flat  horizontal  layers. 

FLO'RA  (flos,floris,  a  flower).  A  term 
expressive  of  the  botanical  productions 
of  any  particular  country. 

FLO'RETS.  Flosculi.  The  small 
flowers  which  compose  the  capitulum  of 
Compositae.  Those  of  the  circumference 
are  ligulate,  or  strap-shaped;  those 
within  the  circumference  are  tubular; 
the  former  are  called  florets  of  the  ray, 
the  latter  florets  of  the  disk. 

FLOS-FERRI.  A  radiated  variety  of 
carbonate  of  lime,  or  of  calc-spar,  often 
found  in  veins  of  spathose  *>ora-ore. 

FLOWER.  In  botanical  language,  the 
flower  is  a  terminal  bud  comprising  all 
the  organs  which  contribute  to  the  pro- 
cess of  fecundation,  as  the  calyx,  the 
corolla,  the  stamens,  and  the  pistil ;  of 
these,  the  last  two  only  are  indis- 
pensable. 

FLOWERS  (in  Chemistry).  A  term 
formerly  used  to  denote  such  bodies  as 


FLU 


FOC 


assume  a  pulverulent  form  by  sublima- 
tion or  crystallization  :  thus  we  have 
flowers  of  zinc,  or  the  oxide ;  flowers  of 
benjamin,  or  benzoic  acid ;  flowers  of 
sulphur,  or  sublimed  sulphur,  &c. 

FLU'CERINE.  The  native  deutoxide 
of  cerium,  occurring  near  Falun,  in 
Sweden. 

FLU'ELLITE.  A  rare  mineral,  con- 
sisting of  hydrofluoric  acid  and  alumina, 
occurring  at  Stenna-gwyn,  in  Cornwall. 

FLUENT  or  FLOWING  QUANTITY. 
This  term  denotes,  in  analysis,  the  vari- 
able quantity,  considered  as  increasing 
cr  diminishing.  The  term  is  now  super- 
seded by  that  of  integral,  and  the  methods 
of  fluxions  and  fluents  have  been  laid 
aside  for  the  differential  and  integral 
calculus. 

FLUID.  A  fluid  is  a  collection  of 
material  particles,  which  are  held  to- 
gether by  so  slight  a  degree  of  cohesion, 
as  to  be  easily  moved  among  themselves. 
1.  Elastic  fluids  are  those  which  are  ca- 
pable of  being  compressed  into  a  smaller 
bulk,  and  of  recovering  their  dimensions 
when  the  compressing  force  is  removed ; 
of  this  kind  are  atmospheric  air  and  all 
the  gases.  2.  Inelastic  fluids  are  those 
formerly  supposed  to  be  incompressible, 
and  among  these  were  ranged  water, 
mercury,  alcohol,  and  liquids  generally. 
But  the  term  is  incorrect :  the  phenome- 
non of  the  transmission  of  sound  through 
water  and  other  liquids  had  long  ago 
indicated  that  they  were  capable  of  being 
compressed. 

FLUI'DITY  {fluo,  to  flow).  The  state 
of  bodies  when  their  parts  are  very  readily 
moveable  in  all  directions  with  respect  to 
each  other.  There  is  a  partial  fluidity, 
in  which  the  particles  are  condensed  or 
thickened  into  a  coherent  though  tremu- 
lous mass.  Jellies  are  of  this  kind,  and 
may  be  considered  as  holding  a  middle 
place  between  liquids  and  solids. 

FLUOBO'RIC  ACID.  Fluoride  of 
boron.  A  gas  produced  by  the  decompo- 
sition of  fluor  spar,  by  means  of  vitrified 
boracic  acid. 

FLUOR  SPAR.  The  technical  name 
for  the  fluoride  of  calcium,  a  salt  found 
crystallized  in  cubes  of  various  colours. 
A  compact  variety  occurs  in  Derbyshire, 
which  is  cut  into  ornamental  vases. 

FLU'ORIDES.  Compounds  of  fluorine 
with  the  electro-positive  elements,  ob- 
tained by  treating  the  fluate  of  mercury 
or  of  lead  with  bodies  more  positive  than 
these  metals. 

FLU'ORINE.  An  elementary  body 
139 


generally  found  in  the  mineral  kingdom 
in  combination  with  calcium,  or  as  fluor- 
ide of  calcium,  which  constitutes  the 
mineral  fluor  spar. 

FLUOSI'LICIC  ACID.  Fluoride  of 
silicon.  A  colourless  gas,  produced  by 
the  action  of  hydrofluoric  acid  on  glass. 

FLUX  {fluo,  to  flow).  A  substance 
used  in  Chemistry  and  Metallurgy,  to 
reduce  ores  or  metallic  compounds  to  the 
metallic  state,  by  promoting  their  fusion. 
Alkaline  fluxes  are  generally  employed, 
which  render  the  earthy  mixtures  fusible 
by  converting  them  into  glass.  Black 
flux  is  a  mixture  of  nitre  and  bitartrate 
of  potash ;  white  flux  is  a  carbonate  of 
potash.  Other  fluxes  consist  of  argol, 
charcoal,  and  some  kinds  of  glass. 

FLU'XIONS  {fluxio,  a  flowing).  In 
the  Newtonian  analysis,  fluxions  are  the 
"velocities  of  motions."  More  particu- 
larly defined,  a  fluxion  is  the  magnitude 
by  which  any  flowing  quantity  would  be 
uniformly  increased  in  a  given  portion  of 
time,  with  the  generating  celerity  at  any 
proposed  position,  or  instant,  supposing 
it  thence  to  continue  invariable.  Hence 
it  appears  that  the  fluxions  of  quantities 
are  always  as  the  celerities  by  which  the 
quantities  themselves  increase  in  magni- 
tude. The  method  of  fluxions,  derived 
from  that  of  prime  and  ultimate  ratios, 
has  been  entirely  superseded  by  that  of 
the  differential  calculus. 

FLY  POWDER.  An  oxide  of  arsenic, 
formed  by  the  exposure  of  native  arsenic 
to  the  air,  and  employed,  when  mixed 
with  sugar  and  water,  for  destroying 
flies. 

FLY-WHEEL.  A  large  heavy  wheel 
applied  to  steam  engines  and  other  ma- 
chines, for  the  purpose  of  equalizing  the 
effect  of  the  moving  power.  If  the 
moving  power  slackens,  the  fly-wheel 
impels  the  machine  forward;  if  the  power 
tends  to  impel  the  machine  too  fast,  the 
fly-wheel  slackens  it.  Its  object  is, 
therefore,  to  absorb,  as  it  were,  the  sur- 
plus force  at  one  part  of  the  action  of  the 
machine,  and  to  give  it  out  when  the 
action  of  the  machine  is  deficient.  At 
one  time  it  is  an  impelling,  at  another  a 
retarding  power. 

FOCUS.  The  Latin  term  for  a  hearth 
or  fire-place  ;  hence  it  denotes  any  point 
in  which  light,  or  heat,  is  concentrated. 
In  Optics,  it  is  the  point  where  several 
rays  are  collected,  in  consequence  of  re- 
fraction or  of  reflexion.  In  Geometry 
and  Conic  Sections,  it  is  applied  to  cer- 
tain points  in  the  ellipse,  the  parabola, 


FOL 


FOR 


the  hyperbola,  where  the  radii  from  all 
parts  of  these  curves  meet. 

1.  Foci  of  an  Ellipse.  Two  points  in 
the  transverse  diameter  of  an  ellipse, 
equally  distant  from  its  ends,  and  so 
situate  that,  if  any  point  be  taken  in  the 
circumference  of  the  ellipse,  and  lines 
drawn  from  that  point  to  the  two  foci, 
the  length  of  these  lines,  when  joined 
together,  will  always  be  the  same,  at 
whatever  part  of  the  circumference  the 
point  may  be  taken. 

2.  Foci  of  Mirrors.  1.  The  focus  of  a 
concave  mirror  is  that  point  of  the  axis 
through  which  the  reflected  rays  of  light 
pass ;  the  principal  focus  is  the  focus  of 
parallel  rays.  2.  In  the  convex  mirror, 
the  focus  lies  as  far  behind  the  reflecting 
surface  as  in  the  concave  it  lies  before 
it ;  it  is  generally  call*  d  the  virtual  focus, 
because  it  is  only  an  imaginary  point, 
and  is  not  formed  by  the  actual  union  of 
rays  in  a  focus.  Similar  terms  are  era- 
ployed  in  speaking  of  the  foci  of  lenses. 

3.  Focus,  Geometrical  and  Refracted. 
The  point  in  which  the  rays  of  light,  ac- 
cording to  their  known  laws,  ought  to  be 
concentrated,  when  reflected  from  a  con- 
cave mirror,  or  refracted  through  a  lens, 
is  termed  the  geometrical  focus ;  that  in 
which  they  are  actually  found,  is  the 
refracted  focus.  These  foci  are  separated 
from  each  other  in  proportion  to  the 
degree  of  spherical  aberration. 

4.  Focal  Distance.  In  the  concave 
mirror,  this  is  the  distance  between  the 
focus  and  the  vertex  of  the  mirror,  and 
it  is  always  equal  to  half  the  radius  of 
that  sphere  of  which  the  mirror  forms  a 
segment.  In  the  convex  lens,  it  is  the 
distance  of  the  focus  from  the  surface  of 
the  glass,  or  from  the  optical  centre. 

FO'LIATE  CURVE  {folium,  a  leaf). 
A  curve  line  of  the  third  order,  defined 
by  the  equation  xs+y3=axy.  It  is  one 
of  the  species  of  defective  hyperbolas, 
having  one  asymptote  and  two  infinite 
branches.  Its  name  is  derived  from  the 
resemblance  of  its  figure  to  that  of  a  leaf. 

FO'LIATED  {folium,  a  leaf).  Resem- 
bling a  leaf.  The  external  surface  of  a 
shell  is  said  to  be  foliated,  when  its  va- 
rices or  spines  are  divided  at  their  mar- 
gins into  leaf-like  segments,  as  in  the 
rose-bush  murex.  The  substance  of  a  bi- 
valve shell  is  also  said  to  be  foliated, 
when  it  consists  of  thin  flat  plates 
overlapping  each  other. 

FO'LIATED  COAL  [foliatus,  having 
the  texture  of  leaves).  A  sub-species  of 
black  coal,  occurring  in  the  coal  forma- 
140 


I  tions,  and  distinguished  by  its  lamellar 
concretions,  splendent  lustre,  and  easy 
frangibility. 

FOLIA'TION  {folium,  a  leaf).  A  term 
synonymous  with  vernation,  denoting  the 
manner  in  which  the  young  leaves  of 
plants  are  arranged  in  the  leaf-bud.  The 
terms  expressive  of  the  various  modes  of 
arrangement  of  leaves  are  the  same  as 
those  employed  for  the  floral  envelopes, 
and  will  be  found  under  the  word  Esti- 
vation. 

FO'LIOLE  {foliolum,  a  little  leaf).  A 
leaflet;  a  term  applied,  in  Botany,  to  the 
small  leaves  which  are  borne  on  the 
several  divisions  of  what  is  commonly 
called  a  compound  leaf. 

FO'LLICLE  (dim.  of  follis,  a  pair  of 
bellows).  Literally,  a  little  bag,  or  scrip 
of  leather.  The  term  denotes,  in  Botany, 
a  one-celled,  one-valved,  superior  fruit, 
dehiscent  along  its  face,  as  in  paeon ia. 

Double  Follicle.  This  term  is  applied 
by  Mirbel  to  the  conceptaculum  of  other 
writers,  and  consists  of  a  two-celled,  su- 
perior fruit,  separating  into  two  portions, 
the  seeds  of  which  do  not  adhere  to  mar- 
ginal placentas,  as  in  the  follicle,  but 
separate  from  their  placentas,  and  lie 
loose  in  each  cell,  as  in  asclepias. 

FO'MALHAUT.  A  star  of  the  first 
magnitude  in  the  southern  constellation 
Piscis  Australis. 

FORA'MEN  {foro,  to  pierce).  An 
opening.  A  passage  observed  at  the 
apex  of  the  ovule  in  plants,  and  com- 
prising both  the  exostome  and  the  en- 
dostome. 

FORAMINI'FERA  {foramen,  an  open- 
ing, fero,  to  bear).  The  name  of  a  family 
of  microscopic  shells,  the  chambers  of 
which  communicate  with  each  other  by 
a  small  opening  or  foramen.  They  are 
not  all  cephalopods,  as  D'Orbigny  sup- 
posed, who  gave  them  the  name. 

FORCE.  The  general  designation  of 
any  exertion  which  has  a  tendency  to 
move  a  body  at  rest,  or  to  affect  or  stop 
the  progress  of  a  body  already  in  motion. 
This  is  sometimes  termed  active  force,  in 
contradistinction  to  that  which  merely 
resists  or  retards  the  motion  of  a  body, 
but  is  itself,  apparently,  inactive.  The 
degree  of  resistance  to  any  motion  may 
be  measured  by  the  active  force  required 
to  overcome  that  resistance,  and  hence 
writers  on  Mechanics  make  use  of  the 
terms  resisting  forces  and  retarding  forces. 
The  straight  line  in  which  any  force 
tends  to  make  a  body  move,  is  termed 
the  line  of  direction  of  the  force. 


FOR 


FOR 


1.  Forces,  Composition  of.  An  expres- 
sion employed  in  Mechanics,  when  two 
or  more  forces  act  on  a  body  in  the  same 
direction,  or  in  diametrically  opposite 
directions,  or  at  some  angle.  In  all  these 
cases,  the  force  which  represents  the 
combined  effects  of  all  the  forces  is  called 
the  resultant.  1.  In  the  first  case,  the 
resultant  is  the  sum  of  all  the  forces,  and 
the  line  of  direction  is  one  and  un- 
changed. 2.  In  the  second  case,  the 
body  will  remain  at  rest,  if  the  forces  are 
equal;  but  if  they  are  unequal,  the  re- 
sultant is  the  difference  of  the  forces,  and 
the  direction  that  of  the  greater  force. 
3.  In  the  third  case,  the  resultant  is  a 
mean  force  in  an  intermediate  direction. 
Thus  any  number  of  forces  may  be  re- 
solved into  one  resulting  force,  the  effect 
of  which  is  the  absolute  motion ;  and  any 
motion  may  be  assumed  to  be  the  result 
of  a  single  force,  or  of  a  combination  of 
many.  This  is  termed  the  composition 
and  resolution  of  forces. 

2.  Forces,  Parallelogram  of.  A  term 
used  as  explanatory  of  the  third  case  in 
the  preceding  paragraph.  If  the  lines 
which  each  of  two  forces,  acting  singly, 
would  have  caused  a  body  to  describe  in 
a  given  time,  make  any  angle  whatsoever 
with  each  other,  the  line  which  the  body 
will  describe  in  that  time,  when  both  the 
forces  act  upon  it  at  the  same  instant,  is 
the  diagonal  of  the  parallelogram  under 
the  two  first-mentioned  lines. 

3.  Force,  Accelerated.  The  increased 
force  which  a  body  exerts,  in  consequence 
of  the  acceleration  of  its  motion.  By 
some  writers  this  is  termed  accumulated 
force.    See  Acceleration. 

4.  Forces,  External  and  Internal.  The 
former  are  those  which  act  upon  masses 
of  matter  at  sensible  distances,  as  attrac- 
tion and  repulsion.  The  latter,  or  mole- 
cular forces,  are  those  which  act  only 
on  the  constituent  molecules  of  matter, 
and  at  insensible  distances,  as  cohe- 
sion. 

5.  Force,  Centrifugal  and  Centripetal. 
The  tendency  of  the  planets  to  move 
forward  in  a  straight  line,  is  called  the 
centrifugal  force,  and  the  attraction  of 
the  sun,  by  which  they  are  drawn  down- 
wards, or  towards  a  centre,  is  called  their 
centripetal  force ;  and  it  is  by  these  two 
forces  that  the  planets  are  made  to  per- 
form their  constant  revolutions  around 
the  sun. 

6.  Forces,  Polar.  Those  forces  which 
are  conceived  to  act  with  equal  intensity 
in  opposite  directions  at  the  extremities 

141 


of  the  axes  of  molecules,  or  of  masses  of 
matter 

FO'RCER.  A  solid  piston,  employed 
in  the  construction  of  pumps  for  pro- 
ducing a  constant  stream,  or  raising 
water  to  a  greater  height  than  it  can  be 
raised  by  atmospheric  pressure. 

FORE-STAFF.  An  instrument  used 
at  sea  for  taking  the  altitudes  of  the 
celestial  bodies.  It  is  now  superseded 
by  more  perfect  instruments. 

FOREST  MARBLE.  A  portion  of 
the  series  of  the  Lower  Oolite  Formation, 
consisting  of  a  coarse  laminated  shelly 
oolite,  interposed  between  beds  of  clay, 
sand,  and  grit. 

FORFICU'LIDuE  {forficula,  a  forked 
claw).  A  family  of  orthopterous  insects, 
named  from  the  genus  forficula,  and 
constituting,  according  to  some  writers, 
the  order  Dermaptera.  They  comprise 
the  various  species  of  earwig. 

FORM.  The  mode  in  which  an  object 
is  presented  to  our  mind  or  senses :  in 
the  former  case  it  belongs  to  the  catc 
gories ;  in  the  latter  to  figure. 

FORMATION.  A  group  of  alluvial 
deposits,  sedimentary  strata,  or  igneous 
rocks,  referred  to  a  common  origin  or 
period.  In  geological  treatises,  one  or 
more  simple  minerals  constitute  a  rock ; 
one  or  several  rocks,  united  by  certain 
common  characters,  constitute  a  forma- 
tion, or  connected  series ;  and  several 
formations  constitute  a  system  of  rocks. 

FO'RMIC  ACID  {formica,  an  ant). 
A  peculiar  acid  extracted  from  red  ants, 
and  procured  artificially  from  all  vege- 
table substances  by  oxidation  with  acids. 
Its  salts  are  called  formiates. 

FORMI'CID^  (formica,  an  ant).  The 
Ant  tribe;  a  family  of  Hymenopterous 
insects,  distinguished  by  their  subterra- 
nean habits,  and  the  existence  among 
them  of  neuters,  which  perform  the  la- 
bours of  the  family. 

FORMULA  (dim.  of  forma,  a  form). 
A  short  general  form  or  rule  for  the  per- 
formance of  any  operation.  In  Algebra, 
the  expression  of  a  general  rule  for  the 
solution  of  a  problem. 

FORMULAE,  CHEMICAL.  A  simple 
mode  of  exhibiting  the  composition  of  che- 
mical combinations  by  representing  the 
substances  by  the  initial  letters  of  their 
Latin  names,  and  adding  figures  or  lines 
to  indicate  the  number  of  equivalents. 
Thus  K.  denotes  one  equivalent  of  po- 
tassium ;  O5,  five  equivalents  of  oxygen ; 
N  or  N,  two  equivalents  of  nitrogen. 
For  every  equivalent  of  oxygen  a  dot,  for 


FO  U 


FRA 


every  equivalent  of  sulphur,  a  comma  is 
placed  over  the  symbol ;  thus  C  repre- 
sents   carbonic   acid;    K,    sulphuret  of 


potassium  ;  K  N.  nitrate  of  potassa. 

FO'RMYL.  A  hypothetical  radical  of 
a  series  of  compounds,  one  of  which  is 
formic  acid. 

FORNAX  CHEMICA.  The  Chemist's 
Furnace ;  a  modern  southern  constella- 
tion, consisting  of  fourteen  stars,  and 
situated  immediately  below  Cetus. 

FORNIX.  Literally,  an  arch ;  a  term 
applied  to  an  assemblage  of  small  plates, 
or  lamellae,  which  overarch  the  orifice  of 
the  tube  of  the  flower  in  certain  plants, 
as  cynoglossum. 

FO'RSTERITE.  A  crystallized  mine- 
ral containing  silica  and  magnesia,  found 
atVesu vius,  accompanied  by  pleonaste  and 
pyroxene,  and  named  from  Mr.  Forster. 

FO'SSIL  (fossilis,  dug  out  of  the 
earth).  Any  thing  dug  out  of  the  earth. 
The  term  is  now  restricted  to  "  organic 
remains,"  or  the  petrified  remains  of  ani- 
mal and  vegetable  substances  found  im- 
bedded in  the  strata  of  the  earth. 

FOSSIL  COPAL.  Highgate  resin.  A 
mineral  of  a  resinous  odour,  found  in  the 
bed  of  blue  clay  at  Highgate,  near  Lon- 
don, and  at  Wocklow  in  Moravia. 

FOSSILI'FEROUS  (fossilis,  dug  out 
of  the  earth,  fero,  to  bear).  A  term  ap- 
plied to  a  formation  or  rock  containing 
organic  remains,  or  fossils,  while  those 
rocks  in  which  no  such  relics  are  found 
are  called  non-fossiliferous. 

FOSSO'RES  (fossor,  a  digger).  Dig- 
gers ;  a  general  term  for  a  group  of  acu- 
leate hymenopterous  insects,  commonly 
known  as  sand  and  wood  wasps,  which 
dig  cells  in  the  earth  or  in  wood,  for  the 
deposition  of  their  eggs  and  stores. 

FOUNDING.  The  mechanical  art 
which  comprises  all  the  operations  of 
reducing  ores,  and  of  smelting  and  cast- 
ing metals. 

FOURTH.  One  of  the  harmonica! 
intervals  of  music,  containing  four  sounds 
or  terms  between  its  extremes,  and  three 
intervals ;  or  as  being  the  fourth  in  order 
from  the  fundamental  sound  in  the  na- 
tural or  diatonic  scale.  The  diminished 
fourth  consists  of  a  whole  tone  and  two 
semitones;  the  perfect  fourth,  of  two 
whole  tones  and  a  semitone ;  the  super- 
fluous fourth,  extreme  sharp,  or  tritonus, 
of  three  whole  tones. 

FOUSEL   OIL.     Hydrate  of  oxide  of 
cmyl.    Oil  of  grain-spirits  or  potatoes ; 
142 


an  oil  produced  in  the  fermentation  of 
unmalted  grain  and  potatoes. 

FOVI'LLA.  A  viscous  liquor  con- 
tained in  the  pollen-vesicle  of  plants. 

FRACTION  (fractio,  a  breaking).  An 
arithmetical  quantity  which  represents  a 
part  or  parts  of  an  integer,  or  whole 
number.  A  vulgar  fraction  is  expressed 
by  means  of  two  numbers  placed  one  over 
the  other,  with  a  line  between  them  ;  the 
lower  of  these  is  the  denominator,  and 
shows  into  how  many  equal  parts  the 
integer  is  divided  ;  the  upper  is  the  nu- 
merator, and  shows  how  many  of  these 
parts  are  taken  to  form  the  fraction,  as  |. 

1.  A  proper  fraction  is  one  whose  nu- 
merator is  less  than  the  denominator,  and 
which  is  itself  therefore  less  than  the 
whole  in  question,  as  f.  An  improper 
fraction  is  one  whose  numerator  is  equal 
to  or  greater  than  the  denominator,  and 
which  is  itself  therefore  equal  to  or 
greater  than  the  whole  in  question,  as 

I,  V- 

2.  A  mixed  number  is  one  formed  of  a 
whole  number  and  a  fraction,  as  2§.  A 
compound  fraction  is  a  fraction  of  a  frac- 
tion, as  f  of  f .  A  complex  fraction  is  one 
in  which  either  the  numerator  or  deno- 
minator, or  both,  are  fractions,  as — 

3£         2_         1|        g  of  3 
1»       4§'       3f'  2i   * 

3.  A  continued  fraction  is  one  whose 
denominator  is  continued  by  being  itself 
a  mixed  number,  and  the  denominator  of 
the  fractional  part  again  continued  as 
before,  and  so  on ;  as — 

1  5  1 

~T       "T  i 

2+ 3  +  —  p  + 

1  9+&c.  1 

3  +  —  2  +  —' 

4  r  +  &c. 

4.  A  vanishing  fraction  is  one  in  which 
a  supposition  is  made  which  destroys 
both  numerator  and  denominator  at  the 
same  time  ;  thus, 

a;2  — 1 


x—l 
is  a  fraction  which  will  assume  the  form 

of  _,  when  x  =  I. 
0 
FRACTURE  (fractura,  a  breaking). 
A  term  employed  in  geology  to  designate 
the  appearance  of  a  fresh  surface  of  a 
rock,  when  exposed  by  the  stroke  of  a 
hammer  or  any  other  forcible  separation 
of  its  parts.  It  may  be  even,  or  form  a 
plane  of  greater  or  less  extent ;  uneven, 
or  formed  of  variously  inclined  planes  of 


FRE 


FRI 


small  extent ;  conchoidal,  when  one  of  the 
separated  surfaces  is  concave,  the  other 
convex ;  splintery,  when  the  surface  pre- 
sents the  appearance  of  thin-edged  scales  ; 
hackley,  when  covered  with  very  sharp 
protruding  points. 

FRAGMENTARY  ROCKS.  Rocks 
formed  of  fragments  of  other  rocks,  gene- 
rally of  sufficient  size  to  admit  of  heing 
distinguished  into  different  kinds.  When 
the  fragments  are  very  small,  they  form 
sandstones  and  tufas;  when  large  and 
rounded,  they  constitute  conglomerates  ; 
when  large  and  angular,  breccice.  The 
fragments  are  commonly  cemented  to- 
gether hy  an  intervening  substance. 

FRANGIBI'LITY.  In  Geology,  the 
degree  of  facility  with  which  a  rock 
yields  to  the  hammer. 

FRA'NKLINITE.  A  mineral  re- 
sembling oxidulous  iron,  occurring  in 
New  Jersey,  together  with  the  red  oxide 
of  zinc. 

FRAU'NHOFER'S  SPECTRUM. 

Fraunhofer  found  that,  in  a  perfect  solar 
spectrum,  the  coloured  spaces  are  not 
continuous,  but  are  interrupted  by  dark 
lines  parallel  to  the  slant  edge  of  the 
prism.  These  lines,  which  are  called 
Fraunhofer's,  are  more  than  500  in  num- 
ber, and  were  employed  by  the  discoverer 
for  accurately  measuring  the  refraction, 
the  breadths  of  the  individual  colours, 
and  the  intensity  of  the  light  of  different 
luminous  bodies. 

FREE  CHARGE.  A  term  applied,  in 
experiments  with  the  Leyden  jar,  or  bat- 
tery, to  that  portion  of  the  induction 
which  is  directed  through  the  air  to  sur- 
rounding conductors. 

FREEZING  MIXTURES.  The  rapid 
absorption  of  heat  which  bodies  exhibit 
in  passing  from  the  solid  to  the  fluid 
state,  explains  the  operation  of  freezing 
mixtures.  If  nitre  be  dissolved  in  water, 
the  temperature  of  the  liquid  falls  above 
16  degrees.  If  snow  and  a  third  of  its 
weight  of  common  salt  be  mixed  toge- 
ther, they  become  liquid,  and  the  tem- 
perature of  the  mixture  may  fall  to  0°. 
These  phenomena  depend  upon  the  affi- 
nity which  exists  between  these  salts  and 
water;  in  order  to  satisfy  this  affinity, 
the  bodies  melt,  and  in  so  doing  absorb 
heat,  which  becomes  latent  in  them, 
from  surrounding  bodies.  By  this  means, 
considerable  degrees  of  cold  may  be  pro- 
duced :  the  degree  of  cold  depends  on 
the  quantity  of  heat  which  passes  from 
a  free  to  a  latent  state ;  and  this,  again, 
depends  upon  the  quantity  of  the  sub- 
143 


stance  liquefied,  and  the  rapidity  of  the 
liquefaction. 

FREEZING  POINT.  A  fixed  point 
in  the  scale  of  the  thermometer,  at  which 
snow  or  ice  melts.  The  length  of  the  de- 
grees depends  on  the  system  of  gradu- 
ation adopted ;  in  Fahrenheit's  ther- 
mometer, the  freezing  point  is  marked 
32°.  The  space  between  the  freezing 
and  the  boiling  point  is  the  fundamental 
distance,  or  length  of  the  scale. 

FRENCH  WHITE.  The  common  de- 
signation of  finely  pulverized  talc. 

FRIABI'LITY'  {frio,  to  crumble).  The 
property  by  which  a  substance  is  capable 
of  being  crumbled  and  reduced  to 
powder. 

FRICTION  {frico,  to  rub).  The  act 
of  rubbing  the  surfaces  of  bodies  upon 
one  another.  In  Mechanics,  it  is  a  hin- 
derance  of  motion,  and  is  termed  a  re- 
tarding force.  Friction  is  said  to  be 
sliding,  when  the  parts  of  one  surface 
move  parallel  with  the  other,  as  when  an 
axle  moves  in  the  nave  of  a  wheel;  and 
rolling,  when  a  round  body  turns  about 
the  surface  of  some  other  body,  so  that 
fresh  points  of  both  the  surfaces  are  con- 
tinually brought  into  contact  with  each 
other. 

Measure  of  Friction.  The  force  re- 
quired to  abrade  the  elevated  parts  of  the 
moving  surfaces,  or  to  raise  them  from 
the  depressions  in  which  they  had  be- 
come lodged.  This  is  usually  found  by 
trying  what  part  of  the  weight  of  the 
moving  body  must  be  exerted  to  maintain 
its  equilibrium,  or  to  overcome  the  re- 
sistance arising  from  this  source.  The 
fraction  expressing  this  ratio  is  called  the 
co-efficient  of  the  friction. 

FRICTION  WHEELS.  A  contriv- 
ance for  diminishing  attrition  by  the  sub- 
stitution of  a  rolling  motion.  The  ex- 
tremities of  an  axle,  instead  of  resting 
in  a  cylindrical  socket,  are  made  to  rest 
on  the  circumference  of  two  revolving 
wheels,  to  which  the  friction  is  trans- 
ferred, and  consequently  diminished  in 
the  ratio  of  the  radius  of  the  friction 
wheels  to  the  radius  of  the  axle. 

FRIESLAND  GREEN.  Brunswick 
green.  Ammoniaco-mnriate  of  copper. 
FRIGID  ZONES.  The  two  divisions, 
or  belts,  of  the  surface  of  the  earth,  which 
lie  between  the  Polar  Circles  and  the 
Poles — one  in  each  hemisphere.  They 
are  so  called  from  their  excessive  cold, 
arising  from  the  total  absence  of  the  sun 
from  them  during  a  great  part  of  the 
year. 


FRU 


FUL 


FRINGT'LLID^  (fringilla,  a  finch). 
The  Finches  ;  a  family  of  the  Insessores, 
or  Perching  birds,  readily  known  by  the 
strength  and  shortness  of  their  conical 
bills.     See  Conirostres. 

FRINGING  REEF.  A  Coral  produc- 
tion, differing  from  the  Barrier  Reef  in 
having  a  comparatively  small  depth  of 
water  on  the  outer  side,  and  a  narrower 
and  shallower  lagoon  channel  between  it 
and  the  main  land. 

FRITH  or  FIRTH  (/return,  a  narrow 
sea).  A  narrow  and  deep  inlet  of  the 
sea,  especially  in  a  rocky  and  elevated 
coast.  Such  an  inlet  is  commonly  called 
a  sound. 

FRITT.  The  mass  produced  by  the 
materials  of  glass,  on  calcination. 

FROND  (frons,  a  branch).  A  term 
applied  to  the  foliaceous  part  of  Ferns  and 
other  Cryptogamic  plants,  from  their 
partaking  at  once  of  the  nature  of  a  leaf 
and  a  branch. 

FRONT  (frons,  frontis,  the  forehead). 
That  part  of  a  shell  near  which  the  head 
of  the  animal  protrudes.  The  term  is 
also  applied  to  the  under  surface  of  spiral 
shells,  where  the  aperture  is  placed,  in 
contra-distinction  to  the  back. 

FRO'NTLET  (frons,  the  front).  The 
margin  of  the  head  behind  the  bill  of 
birds,  generally  covered  with  stiff  bris- 
tles. 

FROST.  The  water  or  vapour  of  the 
atmosphere  congealed  by  cold.  Hoar- 
frost is  frozen  dew,  and  indicates  an  in- 
sensible transition  from  dew,  in  conse- 
quence of  reduced  temperature.  Frost- 
smoke  consists  of  frozen  particles  of 
water  floating  in  the  atmosphere  in  the 
form  of  crystallized  spiculae ;  when  these 
occur  in  large  masses,  they  become  ag- 
glutinated together  into  flakes,  and  fall 
to  the  earth  in  the  form  of  snow. 

FRUIT.  In  botanical  language,  the 
fruit  is  the  ovary  or  pistil  arrived  at  ma- 
turity ;  the  term  is  also  extended  to  what- 
ever parts  are  combined  with  the  ovary 
when  ripe.  An  inferior  fruit  is  that  in 
which  the  pericarp  adheres  to  the  calyx ; 
a  superior  fruit  is  that  in  which  no  such 
adhesion  takes  place  :  the  apple  is  an  in- 
ferior, the  orange  a  superior  fruit. 

FRUSTUM.  Literally,  a  fragment. 
A  portion  cut  off  from  any  solid  figure. 
The  frustum  of  a  cone  is  any  part  cut  off 
from  a  cone  which  does  not  contain  the 
vertex ;  otherwise,  the  part  cut  off  would 
be  itself  a  cone.  The  frustum  differs 
from  fragment,  which  is  a  piece  broken  , 
and  from  segment,  which  is  a  piece  cut  off. 
H4 


FRUTEX.  A  shrub;  a  plant  whose 
branches  are  perennial,  proceeding  di- 
rectly from  the  surface  of  the  earth  with- 
out any  supporting  trunk.  When  very 
small,  the  plant  is  termed  fruticulus,  or 
little  shrub. 

FUCFVOROUS  (fucus,  sea-weed,  voro, 
to  eat).  A  term  applied  to  animals  which 
subsist  upon  sea-weed. 

FUGUE.  A  musical  composition,  in 
which  the  subject,  or  brief  air,  passes  suc- 
cessively and  alternately  from  one  part 
to  another,  according  to  certain  rules  of 
harmony  and  modulation. 

FULCRUM.  The  prop,  or  support  on 
which  a  lever  is  sustained,  and  about 
which  it  moves.  In  raising  a  stone,  the 
body  on  which  the  lever  rests,  is  the  ful- 
crum. 

FULGO'RIDiE  (fulgora,  the  lantern- 
fly).  A  family  of  the  trimerous  Homo- 
ptera,  characterized  by  the  large  develop- 
ment of  their  forehead,  in  which  the 
luminosity  of  the  lantern-fly  is  said  to 
exist. 

FULGURA'TION  (fulgur,  lightning). 
A  term  applied,  in  assaying,  to  the  sud- 
den brightening  of  the  fused  globule  of 
gold  or  silver  when  the  last  film  of  oxide 
of  lead  or  copper  leaves  its  surface. 

FU'LGURITE  (fulgur,  lightning).  A 
term  applied  to  a  bore  or  tube  produced 
by  the  passage  of  lightning  into  a  sandy 
soil,  into  which  it  sometimes  penetrates 
to  a  depth  of  twenty  feet,  fusing  the 
gravel  which  it  penetrates. 

FULFGINOUS  (fuligo,  soot  or  smoke). 
A  term  applied  to  vapours  which  possess 
the  property  of  smoke. 

FUL1GULFN.E.  The  Sea  ducks ;  a 
sub-family  of  the  Anatidce,  named  from 
the  genus  fuligula :  they  frequent  the 
sea  principally,  but  many  of  them  are 
also  found  in  fresh-water  lakes  and  deep 
rivers. 

FULLER'S  EARTH.  A  variety  of 
clay,  of  an  unctuous  quality,  forming  a 
part  of  the  Lower  Oolite  Formation.  It 
is  named  from  its  being  employed  by  ful- 
lers to  remove  the  grease  from  cloth 
before  the  soap  is  applied. 

FU'LMINATE  (fulmen,  a  thunder- 
bolt). A  compound  of  the  fulminic  acid 
with  a  base,  detonating  by  heat  or  friction. 

FU'LMINATING  POWDER  (fulmen, 
a  thunder-bolt).  A  general  term  applied  to 
powders  which  fulminate  on  the  applica- 
tion of  heat  or  friction.  Of  this  kind  are 
the  fulminating  gold,  prepared  by  keep- 
ing recently  precipitated  peroxide  of  gold 
in  strong  ammonia  for  a  day  ;   fulmi- 


FUN 


FUS 


noting  mercury,  employed  for  percussion 
caps,  and  obtained  by  dissolving  mercury 
in  nitric  acid,  and  pouring  the  solution 
into  alcohol ;  fulminating  silver,  prepared 
by  leaving  oxide  of  silver  for  a  day  in  a 
strong  solution  of  ammonia. 

FULMINA'TION  {fulmen,  a  thunder- 
bolt). The  explosion  which  takes  place 
in  chemical  bodies  by  heat  or  friction. 

FULMI'NIC  ACID  {fulmen,  a  thunder- 
bolt). A  compound  of  cyanogen,  cor- 
responding in  its  ultimate  composition 
with  cyanic  acid,  and  exploding  when 
heated,  rubbed,  or  struck. 

FUMA'RIC  ACID.  A  monobasic  acid, 
existing  in  fumaria  or  fumitory,  and  pro- 
duced artificially  by  heating  malic  acid. 

FUMING  LIQUOR  (fumus,  smoke). 
A  chemical  mixture,  which  emits  fumes 
or  vapour  on  exposure  to  the  air.  Boyle's 
fuming  liquor  is  the  protosulphuret  of 
ammonium ;  Cadet's  is  procured  by  dis- 
tilling acetate  of  potash  and  arscnious 
acid ;  Libavius's  is  the  anhydrous  bichlo- 
ride of  tin. 

FUNCTION  (fungor,  to  discharge  an 
office).  The  office  of  an  organ  in  the  ani- 
mal or  vegetable  economy,  as  of  the  heart 
in  circulation,  of  the  leaf  in  respiration. 
Animal  functions  are  those  which  relate 
to  the  external  world,  as  the  senses, 
voluntary  motions,  &c.  Vital  functions 
are  those  immediately  necessary  to  life, 
as  those  of  the  heart,  the  brain,  the  lungs, 
which  have  been  termed  the  tripod  of 
life. 

FUNCTION  (in  Analysis).  A  term 
applied  to  an  algebraical  expression  in 
which  a  certain  letter  or  quantity  is  com- 
pounded with  other  letters  or  quantities  : 
the  expression  is  then  said  to  be  a  func- 
tion of  that  letter  or  quantity;  thus  a+x 
and  o2+xs  are,  both,  functions  of  x ;  the 
circumference  of  a  circle  is  the  function 
of  the  radius. 

Functions,  calculus  of.  That  branch 
of  analysis  which  investigates  the  form 
of  a  function,  and  not  its  value  in  any 
particular  case,  nor  the  conditions  under 
which  it  may  have  a  particular  value. 
Thus,  the  calculus  of  func  tions  may  be 
considered  as  similarly  related  to  alge- 
bra, as  algebra  is  to  common  arithmetic. 

FUNDAMENTAL  BASE.  The  root, 
or  lowest  note  of  a  musical  chord,  found 
by  inverting  its  notes  so  as  to  set  them 
in  thirds  above  this  root. 

FUNGACEjE.  The  mushroom  tribe 
of  Cellular  or  Acotyledonous  plants. 
Plants  consisting  of  a  congeries  of  cel- 
lules, chiefly  growing  upon  decayed  sub- 
145 


stances.  Sporules  lying  either  loose 
among  the  tissue,  or  enclosed  in  mem- 
branous cases  called  sporidia. 

FU'NGATES.  The  saline  compounds 
of  a  peculiar  acid  extracted  from  mush- 
rooms. 

FUNGIC  ACID.  An  acid  procured 
from  several  species  of  fungus,  by  ex- 
pressing their  juice,  boiling  it,  forming  an 
extract,  and  treating  it  with  alcohol. 

FUNGIN.  A  whitish  substance  form- 
ing the  base  of  fungi. 

FUNI'CULAR  MACHINE  (funiculus, 
a  little  rope).  A  mechanical  contrivance 
by  which  bodies  are  supported  by  means 
of  force  applied  to  an  assemblage  of 
ropes,  as  in  bracing  the  sails  of  ships. 

FUNFCULUS  (dim.  of  funis,  a  cord). 
The  little  cord,  by  which  the  ovule  of 
plants  is  attached  to  the  placenta,  of 
which,  indeed,  it  is  a  prolongation. 

FURNACE.  A  fire-place  used  for  the 
purposes  of  fusion,  distillation,  sublima- 
tion, and  the  oxidation  and  deoxidation, 
or  reduction  of  metals.  It  is  termed  eva- 
poratory,  when  employed  to  reduce  sub- 
stances into  vapour  by  heat;  reverbera- 
tory,  when  so  constructed  as  to  prevent 
the  flame  from  rising ;  and  forge,  when 
the  current  of  air  is  determined  by  bel- 
lows. 

FUSCIN  (fuscus,  tawny).  A  brownish 
matter  obtained  from  empyreumatic  ani- 
mal oil. 

FU'SCITE  (fuscus,  tawny).  An  opaque 
greyish  or  greenish-black  mineral,  found 
in  Norway,  in  rolled  masses  of  granular 
quartz. 

FUSELOL.  An  oily  liquor  obtained 
from  alcohol,  also  termed  oil  of  grain, 
and,  hypothetically,  hydrate  of  amyl. 

FUSIBI'LITY.  The  property  by  which 
solid  bodies  are  capable  of  assuming 
the  fluid  state  on  the  application  of 
heat. 

FU'SIBLE  METAL.  An  alloy  of  eight 
parts  of  bismuth,  five  of  lead,  and  three 
of  tin.  This  compound,  sometimes  called 
Newton's,  from  the  name  of  its  disco- 
verer, melts  at  the  heat  of  boiling  water, 
and  may  be  fused  over  a  candle  in  a  piece 
of  stiff  paper,  without  burning  the  paper. 
Rose's  fusible  alloy  is  a  similar  com- 
pound. 

FU'SIFORM  (fusus,  a  spindle,  forma, 
likeness).  Spindle-shaped,  thickest  in 
the  middle  and  tapering  to  the  extremi- 
ties, as  the  cells  composing  woody  fibre, 
the  fleshy  part  of  the  long  radish,  &c. 

FU'SIN.E.  Spindle-shells;  a  sub- 
family of  the  TurbinellidcBy  or  Turnip- 
H 


GAL 


GAL 


shells,  named  from  the  typical  g?£us 
fusus,  and  characterized  by  the  remark- 
able length,  generally  equal,  of  the  canal 
and  of  the  spire. 

FUSION  (fusus,  melted,  from  fundo, 
to  pour  out).  The  state  of  melting. 
Substances  which  admit  of  being  fused 
are  termed  fusible,  but  those  which 
resist  the  action  of  fire  are  termed 
refractory.  Fusion  differs  from  lique- 
faction in  being  applied  to  metals  and 


other  substances  which  melt  at  a  high 
temperature. 

1.  Aqueous  Fusion.  The  solution  of 
salts  which  contain  water  of  crystalliza- 
tion, on  exposure  to  heat. 

2.  Dry  Fusion.  The  liquefaction  pro- 
duced by  heat  after  the  water  of  crystalli- 
zation has  been  expelled. 

3.  Igneous  Fusion.  The  melting  of 
anhydrous  salts  by  heat  without  under- 
going any  decomposition. 


G 


GA'BBRO.  The  Italian  name  for  a 
rock  consisting  essentially  of  felspar  and 
diallage,  called  by  the  French  geologists 
euphotide. 

GA'DIDjE  (gadus,  the  cod).  The  Cod 
tribe;  a  family  of  malacopterygious,  or 
soft-spined,  fishes,  distinguished  by  the 
softness  of  all  their  fins,  and  by  the  in- 
sertion of  their  pointed  ventrals  under 
the  throat.  They  comprise  the  cod,  the 
ling,  the  haddock,  the  whiting,  &c. 

GA'DOLINITE.  A  rare  mineral  found 
by  Gadolin  in  Sweden,  containing  yttria, 
oxide  of  cerium,  &c.  When  heated,  it 
appears  to  burn,  emits  light,  and  becomes 
yellow,  but  undergoes  no  change  in 
weight. 

GAGE  or  GAUGE.  A  term  derived 
from  the  Anglo-Saxon,  and  denoting,  in 
Physics,  any  apparatus  for  ascertaining 
dimension.  The  gage  of  the  air-pump  is 
a  barometer,  connected  with  the  machine, 
for  the  purpose  of  determining  the  pres- 
sure of  the  air  within  the  receiver,  and, 
consequently,  the  degree  to  which  the 
air  has  been  rarified. 

GA'HNITE.  Automalite.  A  native 
aluminate  of  zinc,  in  which  the  alumina 
plays  the  part  of  an  acid.  It  is  named 
from  its  discoverer,  Gahn.  A  similar 
combination  occurs  in  spinel,  which  is  an 
aluminate  of  magnesia. 

GALA'CTIC  ACID  (yd\a,  milk).  Lac- 
tic acid.  The  acid  of  milk,  supposed  to 
be  merely  animalized  acetic  acid.  Ga- 
lactin  is  art  ingredient  in  the  sap  of  the 
Galactodendron  utile,  or  Cow-tree  of 
South  America. 

GALATHE'IDjE.  A  group  of  crus- 
taceous  animals,  named  from  the  genus 
Galathea,  and  constituting,  according  to 
Milne  Edwards,  a  transition  from  the 
anomourous  to  the  macrourous  Crustacea, 
146 


more  particularly  approaching  the  por- 
cellancB. 

GA'LAXY  (yuXafmc  kvkXos,  circle  of 
milkiness).  The  Milky  Way;  a  broad 
line  of  light  passing  entirely  round  the 
heavens,  and  named  from  its  milky  white- 
ness. Herschel  supposes  the  sidereal 
universe  to  be  divided  into  clusters  or 
strata  of  stars,  and  the  "  milky  way"  to 
be  that  particular  cluster  or  stratum  in 
which  our  sun  is  placed.     See  Nebula. 

GA'LBULUS.  The  Latin  term  for  the 
fruit  of  the  cypress,  and  employed  by 
Gcertner  as  synonymous  with  strobile, 
from  which  it  differs  only  in  being  round, 
and  having  the  heads  of  the  carpels  much 
enlarged.  The  fruit  of  the  Juniper  is  a 
galbulus,  with  fleshy  coalescent  carpels. 
Desvaux  calls  it  arcesthide. 

GA'LEA.  The  Latin  term  for  a  hel- 
met, and  hence  applied,  in  botany,  to  the 
upper  arched  lip  of  the  corolla  of  several 
labiate  plants,  as  in  Lamium  album. 

GALE'NA  (yaXeb),  to  shine).  Lead- 
glance  ;  the  native  sulphuret  of  lead. 

GA'LIPOT.  A  white  resin  derived 
from  the  pinus  maritima,  consisting 
almost  entirely  of  a  colourless,  crystal- 
lizable  resin,  named  pimaric  acid. 

GA'LLIC  ACID.  An  acid  obtained 
from  gall-nuts,  but  principally  by  decom- 
position of  tannic  acid.  By  the  applica- 
tion of  a  brisk  heat  to  gallic  acid,  the 
pyrogallic  acid  is  obtained  as  a  crystalline 
sublimate ;  and,  on  applying  heat  to  the 
same  acid  by  means  of  an  oil  bath,  the 
metagallic  or  melangalic  acid  of  Berze- 
lius  remains  as  a  fixed  residue  in  the 
retort. 

GALLFCOLjE.  Gall-inhabiters ;  a 
family  of  hymenopterous  insects,  of  the 
section  pupivora,  which  deposit  their  ova 
in  the  leaf-buds  of    several    species  of 


GAL 


GAN 


oak;  the  buds  undergo  a  morbid  action 
enlarge  into  a  globular  form,  consti- 
tuting a  nidus  for  the  larva  of  the  insects, 
and  eventually  become  the  galls  of  com- 
merce. 

GALLI'NjE  [gallus,  a  cock).  Galli- 
naceous birds,  so  named  from  their  affi- 
nity to  the  common  cock,  and  consti- 
tuting the  fifth  order  of  the  class  Aves. 

GALL-INSECTS.  Coccidce.  A  family 
of  homopterous  insects,  the  females  of 
which  are  apterous,  and  assume,  at  the 
period  of  ovi-position,  a  globular  form 
analogous  to  the  galls  produced  by  the 
Gallicolce. 

GALLS.  Protuberances  found  on  cer- 
tain plants,  occasioned  by  the  puncture 
of  an  insect.  They  differ  in  consistency, 
from  the  hard  nut-gall,  to  the  soft  and 
spongy  berry  or  apple-gall.  The  Aleppo 
galls  are  extensively  used  in  dyeing  and 
in  the  manufacture  of  ink.  See  Gal- 
licolce. 

GALT.  A  provincial  name  applied  in 
the  east  of  England  to  a  series  of  beds  of 
chalk  marl,  the  geological  position  of 
which  is  between  the  upper  and  the 
lower  Greensand. 

GALVANISM.  A  form  of  electricity 
named  after  Galvani,  and  usually  elicited 
hy  the  mutual  action  of  various  metals 
and  chemical  agents  upon  each  other. 
The  additional  discoveries  of  Volta  led 
to  the  term  Voltaism,  or  Voltaic  Electri- 
city ;  and  its  effects  on  the  muscles  of 
animals  newly  killed,  suggested  the  term 
Animal  Electricity. 

1.  Galvanic  Circle.  If,  between  two 
plates  of  different  metals,  a  fluid  be  inter- 
posed capable  of  exciting  a  chemical  effect 
on  the  one  plate,  while  it  has  little  or  no 
influence  on  the  other ;  and  if  a  com- 
munication be  then  formed  between  the 
plates  at  some  point,  by  means  of  a  wire 
or  other  conducting  substance,  a  con- 
tinued current  of  electricity  will  pass 
along  the  conductor  from  one  plate  to  the 
other,  so  long  as  the  chemical  action  is 
excited.  This  constitutes  a  simple  gal- 
vanic circle. 

2.  Galvanic  Pile.  This  arrangement 
consists  of  a  number  of  pairs  of  plates, 
similar  to  those  above  described,  placed 
alternately  with  an  acting  fluid  inter- 
vening between  each  pair,  and  having 
the  two  ends  of  the  series  connected  by  a 
wire.  The  effect  is  thus  multiplied  by 
each  pair  of  plates.  The  end  of  the  pile 
which  gives  out  the  electric  fluid  is  called 
the  positive  pole,  while  the  other  end  in 
which  the  wire  terminates,  and  which 

147 


receives  the  electric  matter,  is  called  the 
negative  pole  of  the  pile. 

3.  Galvanic  Battery,  or  Trough.  An 
apparatus  for  accumulating  galvanism, 
consisting  of  plates  of  zinc  and  copper 
fastened  together,  and  cemented  into  a 
wooden  or  earthenware  trough  so  as  to 
form  a  number  of  cells ;  the  trough  is 
then  filled  with  diluted  acid. 

4.  Galvano-meter  (ue-rpov,  a  measure). 
An  instrument  which  indicates  the 
feeblest  polarization  of  the  magnetic 
needle,  or  slightest  current  in  the  con- 
necting wire  of  a  voltaic  circle. 

5.  Galvano-scope  (o-KOTreco,  to  examine). 
An  instrument  by  means  of  which  the 
existence  and  direction  of  an  electric 
current  may  be  detected.  A  magnetic 
needle  is  a  galvanoscope. 

6.  Galvano-magnetic  induction  machine. 
A  machine  principally  used  for  medical 
purposes,  and  consisting  of  an  induction 
spiral  connected  with  a  hydro-electric 
battery,  which  is  fitted  up  with  an  appa- 
ratus for  establishing  and  breaking  con- 
tact with  great  rapidity. 

GA'MMUT.  An  old  term  in  Music, 
now  applied  to  the  diatonic  scale,  and 
also  called  the  harmonical  hand,  in  con- 
sequence of  Guido  having  arranged  the 
musical  notes  upon  the  figure  of  a  hand. 
The  term  gammut,  or  gammfut,  was  de- 
rived from  the  Greek  letter  ydnp.a,  ap- 
plied by  Guido  to  a  note  which  he  added 
below  the  "  supernumerary  "  note,  with 
the  addition  of  ut,  which  is  the  same  as 
do  in  the  syllabic  scale. 

GAMOPE'TALOUS  itaneu,  to  marry, 
TreraXov,  a  petal).  A  term  applied,  in 
Botany,  to  a  corolla  consisting  of  cohering 
petals,  in  order  to  avoid  the  inaccuracy 
of  the  word  mono-petalous. 

Gamo-sepalous.  A  corresponding  term, 
denoting  a  calyx  formed  of  cohering  se- 
pals, and  therefore  preferable  to  the  more 
common  term  mono-sepalous. 

GA'NGLIONE'URA  {^yXtov,  a 
nerve-knot,  vevpov,  a  nerve).  A  term 
applied  by  Rudolphi  to  the  Articulate 
and  Molluscous  divisions  of  the  Animal 
Kingdom,  which  are  characterized  by  a 
ganglionic  disposition  of  the  nervous 
system.  In  the  former  class,  the  ganglia 
are  arranged  symmetrically  along  the 
middle  line  of  the  body,  and  communi- 
cate by  a  double  chord  ;  these  are  termed 
homogangliata.  In  the  latter  class,  the 
ganglia  are  dispersed  in  an  unsymmetri- 
cal  manner,  apart  from  one  another  and 
from  the  middle  plane  ;  these  are  called 
heterogangliata. 

H2 


GAS 


GEM 


GA'NGUE.  A  term  applied  to  the 
stones  found  in  the  cavities  which  form 
the  veins  of  metals,  constituting  the  ma- 
trix of  the  ore. 

GA'NOID  FISHES  (7ai/ov,  splendour, 
et3or,  likeness).  A  group  of  fossil  fishes, 
found  in  the  old  red  sandstone,  and  other 
rocks  of  that  period,  and  named  from  the 
brilliant  lustre  of  their  scales,  which  are 
generally  coated  with  polished  enamel. 
See  Placoid  Fishes. 

GAPING.  A  term  applied  to  a  bivalve 
shell,  when  any  parts  of  the  margins  do 
not  meet  each  other. 

GARNET.  A  simple  mineral,  gene- 
rally of  a  deep  red  colour,  crystallized; 
occurring  most  frequently  in  mica  slate, 
but  also  in  granite  and  other  igneous 
rocks.  Common  garnet  is  less  hard,  and 
less  transparent  than  Precious  Garnet, 
which  is  often  perfectly  diaphanous. 
Resinous  garnet  is  another  name  for  the 
mineral  colophonite. 

GARNET-BLENDE.  Zinc-blende.  A 
sulphuret  of  zinc ;  a  massive  mineral  of 
adamantine  lustre,  and  often  black. 

GAS.  An  old  Teutonic  word,  signifying 
air  or  spirit ;  now  applied  to  permanent 
aeriform  fluids  for  the  purpose  of  distin- 
guishing them  from  common  air,  which 
is  a  mixture  of  two  kinds  of  gas.  Gases 
are  distinguished  from  liquids  by  the 
name  of  elastic  fluids ;  and  from  vapours, 
by  their  retaining  their  elasticity  in  all 
temperatures. 

GASO'METER.  A  gas-holder ;  a  me- 
tallic apparatus  for  containing  a  large 
quantity  of  any  gas  which  is  insoluble 
in  water. 

GASTERO'PODA  (yavrrip,  the  sto- 
mach, 7r63e?,  feet).  The  third  class  of 
the  Mollusca,  including  the  slugs  and 
shell-snails,  and  distinguished  by  the 
structure  and  position  of  their  locomo- 
tive apparatus,  which  consists  of  a  mus- 
cular disc  attached  to  the  ventral  surface 
of  the  body,  serving  either  as  an  instru- 
ment for  crawling,  or,  in  rarer  instances, 
compressed  into  a  muscular  membrane 
for  swimming.  They  may  be  divided 
into  three  orders  by  the  forms  of  their 
respiratory  organs  and  of  their  external 
covering : — 

1.  Nudibranchia,  or  those  which 
breathe  by  branchiae  unprotected  by  an 
external  or  internal  shell. 

2.  Tectibranchia,  or  those  which  have 
the  branchiae  protected  by  an  external 
or  internal  calcareous  covering. 

3.  Pulmonata,  or  those  which  respire 
by  means  of  a  pulmonary  sac. 

148 


GAY-LUSSITE.  A  crystalline  mine- 
ral found  abundantly  in  South  America, 
and  named  from  the  French  chemist  Gay 
Lussac,  who  ascertained  it  to  be  a  double 
carbonate  of  soda  and  lime,  with  5  equi- 
valents of  water. 

GECKO'TIDjE.  The  Gecko  tribe;  a 
natural  family  of  Saurians,  named  from 
the  genus  gecko,  and  characterized  by  the 
peculiar  structure  of  the  foot,  the  sole  of 
which  is  converted  into  a  sucker,  enabling 
the  animal  to  crawl  up  walls  and  along 
ceilings,  after  the  manner  of  the  flies  on 
which  they  feed. 

GE'HLENITE.  A  mineral,  allied  to 
Vesuvian,  found  together  with  calcareous 
spar  in  the  valley  of  Fassa  in  the  Tyrol. 

GE'INE  {yrj'ivos,  earthy).  Geic  acid. 
Another  name  for  humus,  or  vegetable 
mould,  produced  by  the  decomposition  of 
vegetable  matters. 

GELATINE  {gelu,  frost).  An  animal 
or  vegetable  substance,  constituting  the 
principle  of  jelly,  and  distinguished  from 
albumen  by  its  not  becoming  consistent 
by  heat.  The  purest  variety  of  gelatine 
is  isinglass;  the  common  gelatine  of 
commerce  is  glue;  and  the  hydrate  of 
gelatine  is  jelly. 

GE'LATINES.  The  term  applied  by 
Mr.  Kirby  to  the  Acalephcs  of  Cuvier,  or 
the  Radiaires  molasses  of  Lamarck,  from 
the  gelatinous  consistency  of  their  bodies. 

GE'MINI.  The  third  of  the  zodiacal 
constellations,  consisting  of  eighty-five 
stars,  the  principal  of  which  are  Castor 
and  Pollux.  It  denotes  the  third  month 
of  Autumn,  from  the  20th  of  November 
to  the  20th  of  December.  In  the  Egyp- 
tian zodiac  this  sign  is  represented  by  a 
young  man  and  a  girl.  In  this  month 
seeds  germinate.  The  Greek  appellation 
for  this  sign,  6i6v(xot,  is  vague. 

GEMITRFCES  (gemo,  to  moan  or 
coo).  Cooers ;  an  order  of  Birds,  com- 
prising, according  to  Macgillivray,  the 
single  family  of  Columbince,  or  Pigeons, 
and  named  from  their  peculiar  cooing 
sound. 

GE'MMA.  A  leaf-bud,  or  the  rudi- 
ment of  a  young  branch,  consisting  of 
scales  surrounding  a  growing  point,  which 
is  in  direct  communication  with  the 
woody  and  cellular  tissue  of  the  stem. 
This  term,  as  applied  to  zoophytes,  de- 
notes a  young  animal  not  enclosed  in  an 
envelope  or  egg. 

GEMMA,  a  CORONA  BOREALIS. 
Alphacea.  A  star  of  the  second  magni- 
tude in  the  Northern  Crown. 

GEMMI'PAROUS    {gemma,   a   bud, 


GEN 


GEO 


pario,  to  bring  forth).  A  designation  of 
that  mode  of  propagation,  which  takes 
place  by  the  growth  of  the  young,  as  of  a 
bud,  from  the  parent,  as  in  many  of  the 
infusoria. 

GE'MMULE  (dim.  of  gemma,  a  bud). 
A  term  synonymous  with  plumule,  and 
denoting  the  growing  point  of  the  em- 
bryo in  plants.  It  is  also  applied  to  the 
embryo  of  the  radiated  animals  at  that 
stage  of  their  existence  when  they  re- 
semble ciliated  monads. 

GENDER.  In  Grammar,  that  acci- 
dent of  a  noun  which  points  out  the  sex 
or  the  absence  of  sex. 

GENERALIZATION.  The  act  of 
comprehending  under  a  common  name 
several  objects  agreeing  in  some  point 
which  we  abstract  from  each  of  them, 
and  which  that  common  name  serves  to 
indicate.  Each  of  these  names  is  called, 
in  Logic,  a  common  term,  from  its  be- 
longing to  them  all  alike ;  or  a  predicable, 
because  it  may  be  predicated  affirma- 
tively of  them,  or  of  any  one  of  them. 
See  Abstraction. 

GENERATING  FUNCTION.  A  term 
applied  by  Laplace  to  any  function  of  x, 
considered  with  reference  to  the  coeffi- 
cients of  its  expansion  in  powers  of  x. 
It  is  employed  in  solving  equations  of 
differences,  &c. 

GENERATION.  In  Geometry  a  line 
is  said  to  be  generated  by  the  motion  of  a 
point,  a  surface  by  the  motion  of  a  line, 
a  solid  by  that  of  a  surface.  Thus,  a 
sphere  is  generated  by  the  revolution  of 
a  semicircle  about  its  diameter ;  a  circle, 
by  the  revolution  of  its  radius  about  one 
of  its  extremities.  The  figure  thus  gene- 
rated is  termed  the  generant.  From  this 
mode  of  considering  quantity  as  gene- 
rated by  motion,  arose  the  terms  fluxion 
and  fluent  in  infinitesimal  analysis. 

GENI'CULATE  (geniculum,  a  little 
knee  or  joint).  Knee-jointed ;  bent  ab- 
ruptly in  the  middle,  as  the  stems  of 
many  grasses,  the  filament  of  certain 
plants,  &c.  The  term  geniculum  is  ap- 
plied to  the  node,  or  point  of  the  stem 
from  which  the  leaves  are  developed. 

GENITIVE  CASE  {gigno,  to  beget). 
In  Grammar,  the  getting  case,  known  by 
the  sign  of,  and  answering  to  the  ques- 
tion whose,  or  whereof?  It  denotes  the 
relation  of  property,  and  indicates  the 
subject  to  which  a  thing  belongs. 

GENTIANA'CEjE.  The  Gentian  tribe 
of  Dicotyledonous  plants.  Herbaceous 
plants  with  leaves  opposite ;  flowers  ter- 
minal, axillary;  stamens  alternate  with 
149 


the  segments  of  the  corolla;  ovarium 
single,  superior,  1  or  2-celled;  fruit  a 
many-seeded  berry. 

GE'NUS.  In  Logic,  a  predicable  which 
is  considered  as  the  material  part  of  the 
species  of  which  it  is  affirmed.  A  subal- 
tern genus  is  that  which  is  capable  of 
being  a  species  in  respect  of  a  higher 
genus.  A  genus  which  is  not  considered 
as  a  species  of  any  thing,  is  called  sum- 
mum  (the  highest)  genus.  "When  it  is 
said  of  a  magnet,  that  it  is  "a  kind  of 
iron-ore,"  this  is  called  its  proximum 
genus,  because  it  is  the  closest  (or  lowest) 
genus  which  is  predicated  of  it:  " mine- 
ral" is  its  more  remote  genus. — Whately. 

In  Natural  History,  a  genus  denotes  a 
class  of  animals  or  plants  which  possess 
some  common  property.  The  other  per- 
manent differences  between  the  indivi- 
duals of  the  same  genus  constitute  a 
species;  and  the  accidental  differences 
found  among  the  species  are  termed 
varieties. 

GEOCENTRIC  (7n,  earth,  nevrpov, 
the  centre).  Having  the  same  centre  as 
the  earth,  or  having  the  earth  for  its 
centre.  Thus  the  moon's  orbit  is  geo- 
centric ;  but  the  orbits  of  the  other 
planets,  and  of  the  earth  itself,  are  helio- 
centric, having  the  sun  as  their  centre  of 
motion.  The  geocentric  place  of  a  planet 
is  the  place  in  which  it  would  appear  to 
an  eye  in  the  centre  of  the  earth.  The 
geocentric  latitude  of  a  planet  is  its  lati- 
tude as  seen  from  the  earth ;  or  it  is  the 
inclination  of  a  line  connecting  the  planet 
and  the  earth  to  the  plane  of  the  ecliptic. 
The  geocentric  longitude  of  a  planet  is 
the  distance,  measured  on  the  ecliptic,  in 
the  order  of  the  signs,  between  the  geo- 
centric place  and  the  first  point  of  Aries. 

GEOCO'RISA  (fT,,  earth,  Kopts,  a  bug). 
The  Land-bugs ;  a  section  of  Hetero 
pterous  insects,  including  several  families 
which  strongly  resemble  the  Cimicidae, 
or  common  bugs.     See  Hydrocorisa. 

GEO'DES  (Tea>an?,  earthy).  A  variety 
of  aetites,  or  eagle-stone,  the  cavity  of 
which,  instead  of  containing  a  nodule, 
contains  only  loose  earth,  and  is  gene- 
rally lined  with  crystals. 

GEODE'SY  (yeudaiffia,  a  dividing  of 
earth).  A  term  literally  signifying  a 
division  of  the  earth,  and  so  far  synony- 
mous with  geometry,  or  land-measuring. 
In  a  more  general  sense,  however,  it  sig- 
nifies that  branch  of  practical  geometry 
which  comprehends  all  the  operations, 
geometrical  and  trigonometrical,  required 
for  determining  the  general  figure  of  the 
H3 


GEO 


GEO 


earth,  the  figures  and  areas  of  large  por- 
tions of  the  earth's  surface,  and  the 
variations  of  the  intensity  of  gravity  in 
different  regions,  by  means  of  direct  ob- 
servation and  measurement. 

GEO'GRAPHY  (7^,  the  earth,  TPa0&>, 
to  describe).  The  science  which  teaches 
the  knowledge  of  the  earth.  This  is  the 
strict  etymological  meaning  of  the  term, 
which  is  thus  distinguished  from  hydro- 
graphy, or  the  description  of  water,  or 
seas,  which  constitute  the  greater  portion 
of  the  terraqueous  globe.  It  differs  from 
cosmography,  as  a  part  differs  from  the 
whole  ;  from  chorography  and  topography, 
as  a  whole  differs  from  a  part. 

1.  Physical  Geography,  though,  strictly 
speaking,  it  denotes  merely  a  description 
of  the  principal  features  of  the  earth's 
surface,  usually  includes  the  subjects  of 
climate  and  of  temperature,  the  effect  of 
these  agents  on  the  condition  of  the 
human  race,  and,  generally,  an  account 
of  the  animals  and  productions  of  the 
globe.  Hence  it  comprises  the  various 
questions  of  Hydrography,  Meteorology, 
and  Climate. 

2.  Mathematical  Geography  is  that 
branch  of  the  general  science  which  is 
derived  from  the  application  of  mathe- 
matical truths  to  the  figure  and  dimen- 
sions of  the  earth,  to  its  relations  with 
the  celestial  bodies,  to  the  relative  posi- 
tions and  distances  of  places  on  its  sur- 
face, and  to  their  representations  by 
globes  or  maps. 

3.  Political  Geography  relates  to  his- 
tory and  statistics,  and  comprises  all  the 
moral  and  social  conditions  of  nations,  as 
inhabitants  of  the  globe. 

GEO'LOGY  (TJj,  the  earth,  \6yos,  an 
account).  Geognosy.  A  description  of 
the  structure  of  the  earth,  and  of  the 
theories  entertained  respecting  its  forma- 
tion. A  short  tabular  view  of  the  suc- 
cessive geological  periods  is  here  given, 
with  particular  reference  to  the  forms  of 
organic  life  most  strikingly  exhibited  in 
each: — 

I.  The  First  or  Ancient  Epoch. 

1.  The  period  antecedent  to  the  intro- 
duction of  life.  The  deposit  of  non- 
fossiliferous  rocks. 

2.  The  period  of  invertebrated  animals, 
as  the  most  highly  organized  inhabitants 
of  the  sea.     The  Silurian  rocks. 

3.  The  introduction  of  fishes,  the  cha- 
racteristic animals  of  the  second  fossili- 
ferous  period.  The  Devonian,  or  Old 
Red  Sandstone  system  of  Formations. 

150 


4.  The  period  marked  by  the  presence 
of  vegetables  and  the  first  introduction 
of  reptilian  animals.  The  Permian  and 
Carboniferous  Systems. 

II.  The  Middle  Epoch. 

5.  The  periods  of  the  frog-like,  bird- 
like, and  marine  reptiles.  The  formation 
of  the  New  Red  Sandstone,  or  Triassic 
Series.  Animals  characteristic  of  the 
Lias  Formation. 

6.  The  periods  of  the  gigantic  land 
reptiles,  the  flying  reptiles,  the  gigantic 
crocodilians,  and  the  first  introduction  of 
mammalian  animals.  Wealden  and  Oolitic 
Formations. 

7.  The  periods  of  the  Chalk  and  Green- 
sand,  during  the  deposit  of  which  there 
was  probably  a  deep  sea,  covering  a  large 
proportion  of  the  existing  land.  Creta- 
ceous Period. 

III.  The  Modern  Epoch. 

8.  The  period  of  the  pachydermatous 
animals  of  the  Paris  basin,  and  of  the 
sub-tropical  (?)  fruits  and  animals  of  the 
London  and  Hampshire  basins.  Older 
Tertiary  System. 

9.  The  period  of  various  large  animals 
of  the  Middle  Rhine  valley,  succeeded 
by  that  of  the  mastodon  and  elephants 
in  North  America,  England,  Northern 
Europe,  and  India.  Middle  Tertiary 
System. 

10.  The  period  of  the  caverns  and 
gravel;  with  Carnivora,  the  Megaceros 
and  other  gigantic  ruminating  animals, 
and  the  elephants  of  Europe;  and  of 
various  gigantic  animals  in  Asia,  Ame- 
rica, Australia,  and  New  Zealand.  Newer 
Tertiary  System. 

GEO'METRY  {^eui^erpia,  land-mea- 
suring). The  etymological  meaning  of 
this  term  seems  to  imply  that  the  mea- 
surement of  land  was  the  most  important, 
perhaps  the  only,  use  to  which  this 
science  was  at  first  applied.  It  now  em- 
braces the  measurement  of  the  earth  and 
of  the  heavens ;  and  it  forms,  with  Arith- 
metic, the  basis  of  all  accurate  conclusions 
in  the  mixed  sciences. 

Geometry,  Descriptive.  A  term  em- 
ployed by  Monge  to  denote  a  systematized 
method  of  geometry,  by  which  a  ground- 
plan  and  an  elevation  are  made  to  give 
the  form  and  dimensions  of  a  building. 
The  projections  of  a  point  upon  two 
planes  at  right  angles  to  each  other, 
called  the  planes  of  projection,  being 
given,  the  position  of  the  point  itself  is 
given. 


GIB 


GL  A 


GEO'RGIUM  SIDUS.  The  name 
given  by  Herschel  to  the  planet  dis- 
covered by  himself  in  1781 ;  it  is,  how- 
ever, more  generally  known  by  the  name 
of  its  discoverer,  or  by  that  of  Uranus. 

GE'OTHERMO'METER  (in,  the 
earth,  thermometer).  An  instrument  in- 
vented by  Magnus,  for  measuring  the 
degree  of  terrestrial  heat  at  different 
places,  especially  in  mines  and  Artesian 
wells.  The  temperature  appears  to  rise 
1°  F.  for  every  60  or  70  feet  of  descent 
below  the  surface ;  hence,  at  a  depth  of  a 
few  miles,  the  earth  must  be  in  a  state  of 
incandescence. 

GERANIA'CE^E.  The  Geranium  tribe 
of  Dicotyledonous  plants.  Herbaceous 
plants  or  shrubs,  with  stems  tumid  and 
separable  at  the  joints;  stamens  mona- 
delphous ;  fruit  composed  of  five  cocci, 
each  terminated  by  an  indurated  style, 
consolidated  round  a  long  beak-like  axis, 
from  which  they  separate  with  elasticity, 
when  ripe,  by  the  rolling  back  of  the 
styles. 

GERMAN  SILVER.  Packfong.  A 
white  alloy  of  nickel,  formed  by  fusing 
together  100  parts  of  copper,  60  of  zinc, 
and  40  of  nickel. 

GE'RMEN.  The  term,  applied  by 
Linnaeus  to  the  ovary  of  plants,  or  the 
hollow  case  forming  the  base  of  the  pistil, 
enclosing  the  ovules,  and  always  contain- 
ing one  or  more  cells  or  cavities. 

GERMINA'TION  (germino,  to  bud). 
A  term  applied  by  botanists  to  that  func- 
tion by  which  the  embryo  contained  in 
the  seed  is  first  called  into  life. 

GEY'SER.  A  boiling  fountain  in  Ice- 
land, which  frequently  throws  out  its 
contents  to  the  height  of  more  than  a 
hundred  feet,  sometimes  to  thrice  that 
elevation. 

GIANTS'  CAUSEWAY.  A  columnar 
basaltic  formation  on  the  northern  coast 
of  Antrim  in  Ireland,  connected  with  a 
trap  district  which  occupies  almost  the 
whole  of  the  county,  &c,  comprehending 
an  area  of  about  800  square  miles  on  both 
sides  of  the  valley  of  the  Bann. 

GFBBOUS  (gibbus,  protuberant). 
Humped ;  a  term  applied  to  the  convex- 
ity of  a  solid  body,  and  used  in  reference 
to  the  enlightened  parts  of  the  moon, 
whilst  she  is  moving  from  her  first 
quarter  to  the  full,  and  from  the  full  to 
the  last  quarter.  In  Zoology,  any  part 
of  a  shell  more  particularly  elevated 
above  the  surface,  or  unusually  so  in 
comparison  with  other  species,  is  termed 
gibbous,  as  in  strombus  gibbosus. 
151 


GIE'SECKITE.  A  granular  mineral 
brought  from  Greenland  by  Sir  C. 
Giesecke. 

GI'NGLYMOID  (7^77X^6?,  a  hinge, 
et'3o?,  likeness).  Hinge-like ;  a  term  ap- 
plied to  a  joint  formed  for  motion  on  one 
plane. 

GI'RASOL.  A  term  derived  from  the 
Italian  giro-sole,  or  turn-sun,  and  applied 
to  a  milk-white  or  bluish  opal,  which 
reflects  a  reddish  colour  when  turned  to 
the  sun.  The  term  has  been  corrupted 
into  Jerusalem,  as  applied  to  a  species  of 
sunflower,  the  helianthus  tuberosus,  vul- 
garly said  to  turn  its  flowers  to  the  sun. 

GLA'CIAL  ACID  (glades,  ice).  The 
strongest  acetic  acid  which  can  be  pro- 
duced. It  exists  in  a  crystallized  state 
under  50° Fahr., and  contains  79  percent, 
of  real  acid. 

GLA'CIER  (glace,  ice).  An  accu- 
mulation of  ice  and  hardened  snow, 
occurring  in  the  valleys  and  on  the  slopes 
of  the  Alps  and  other  lofty  mountains. 
Saussure  distinguishes  two  kinds  of  gla- 
cier ;  viz.  those  contained  in  the  valleys 
more  or  less  deep,  and  which,  though  at 
great  elevations,  are  still  commanded  on 
all  sides  by  mountains  higher  still ;  and 
those  not  contained  in  the  valleys,  but 
spread  out  on  the  slopes  of  the  higher 
peaks.    See  Moraine. 

GLA'CIS.  A  term  borrowed  from  the 
language  of  fortification,  in  which  it  de- 
notes an  easy  insensible  slope  or  decliv- 
ity, less  steep  than  that  of  a  talus. 

GLAI'RINE.  A  term  referred  by  some 
to  a  gelatinous  vegetable  matter ;  by 
others  to  a  pseud-organic  substance 
formed  on  thermal  waters. 

GLANCE  (glanz,  splendour).  A  de- 
signation of  certain  minerals  which  have 
a  metallic  or  pseudo-metallic  lustre,  as 
glance-coal,  lead-glance,  &c. 

GLANCE-COAL.  Anthracite.  A  va- 
riety of  coal  which  burns  without  flame 
or  smell.  It  occurs  in  beds  in  clay-slate, 
greywacke,  and  alum-slate,  but  most 
abundantly  in  secondary  rocks,  as  in  coal 
and  trap  formations.  Slaty  glance-coal 
is  another  variety,  called  in  this  country 
blind  coal.  A  third  variety  occurs  in 
basaltic  columnar  rows,  near  Cumnock 
in  Ayrshire. 

GLAND  (glans,  an  acorn).  In  Botany, 
a  small  mass  of  firm  cellular  tissue, 
which  is  often  much  harder  and  more 
coloured  than  that  which  surrounds  it. 
It  may  be  simple  or  compound,  stalked 
or  sessile.  Glands  are  termed  utricular, 
when  they  appear  as  elevated,  distended 
H4 


GLA 


GLO 


bladders  of  the  epidermis ;  lenticular, 
when  they  exist  as  brown  oval  spots  upon 
the  bark;  internal,  when  of  the  nature 
of  cysts  or  nuclei  situated  below  the 
cuticle;  &c.  The  disk,  or  fleshy  body 
which  surrounds  the  base  of  the  ovary 
in  certain  plants,  is  commonly  called  a 
hypogynous  gland. 

GLANS.  In  Botany,  a  compound  in- 
ferior fruit,  with  a  dry  pericarp,  one- 
celled,  but  proceeding  from  an  ovary 
which  contains  several  cells,  and  seated 
in  a  persistent  involucre  called  a  cupule. 
The  gland  is  solitary  in  the  oak ;  in  the 
beech  and  the  sweet  chestnut  there  are 
several,  completely  enclosed  in  the  cu- 
pule. The  gland  is  termed  calybio  by 
Mirbel,  and  nucula  by  Desvaux. 

GLASS.  The  varieties  of  glass  derive 
their  vitreous  character  from  the  silicates 
of  potash  and  soda.  Green  or  bottle- 
glass  consists  of  the  silicates  of  alumina, 
of  the  oxides  of  iron,  magnesia,  and 
potash  or  soda.  Flint-glass  is  a  silicate 
of  potash  and  lead.  Window-glass  is 
a  silicate  of  soda  and  lime.  Plate-glass 
used  for  mirrors,  crown-glass,  and  the 
beautiful  Bohemian  glass,  are  silicates  of 
potash  and  lime. 

The  term  glass  is  also  applied  to  glassy 
substances,  as  the  glass  of  antimony,  or 
the  sulphuret;  Muscovy  glass,  or  mica; 
tin  glass,  or  bismuth,  &c. 

GLASS-GALL.  Sandiver.  The  salt 
scum  which  floats  on  the  surface  of  fused 
glass. 

GLAUBER'S  SALT.  Native  sulphate 
of  soda,  occurring  together  with  rock 
salt  and  Epsom  salt,  on  the  borders  of 
salt  lakes,  and  dissolved  in  the  waters  of 
lakes  and  of  the  ocean,  &c.  Glauber's 
secret  sal  ammoniac  is  a  sulphate  of  am- 
monia, a  constituent  of  soot  from  coal. 

GLAU'BERITE.  A  crystallized  salt, 
consisting  of  nearly  equal  parts  of  the 
sulphates  of  lime  and  of  soda,  and  found 
imbedded  in  rock  salt  brought  from 
South  America  and  from  Spain. 

GLAUCIC  ACID  (^Xauxif,  blue,  sea- 
green).  An  acid  procured  from  the  teazle 
and  scabious  plants. 

GLAU'COLITE  {yXavKot,  blue,  \i0os, 
a  stone).  A  bluish-green  mineral,  found 
near  lake  Baikal  in  Siberia,  and  consist- 
ing of  a  silicate  of  alumina  and  lime. 

GLAU'CONIE  (yXavKas,  blue,  sea- 
green).  A  French  term  applied  by 
Brongniart  to  some  stratified  deposits 
associated  with  chalk,  which  correspond 
with  the  green  sands  of  English  geo- 
logists. 

152 


GLI'ADINE  (y\ia,  glue).  Vegetable 
albumen ;  one  of  the  constituents  of 
gluten.     See  Zymome. 

GLIMMER.  A  name  occasionally 
applied  to  micaceous  earths. 

GLIRES  (glis,  a  dormouse).  The 
fourth  order  of  the  Mammalia  in  the 
Systema  Natures  of  Linnaeus,  comprising 
the  porcupines,  hares,  beavers,  mice, 
squirrels,  bats,  &c,  characterized  by  the 
presence  of  two  long  chisel-shaped  in- 
cisors in  each  jaw.     See  Rodentia. 

GLOBE  (globus,  a  ball).  A  round  or 
spherical  body,  bounded  by  one  uniform 
convex  surface,  every  point  of  which  is 
equally  distant  from  a  point  within, 
called  the  centre. 

1.  Artificial  Globes  are  instruments 
employed  for  conveying  the  first  ideas  of 
the  figure  and  rotation  of  the  earth,  of 
latitude  and  longitude,  and  of  the  situa- 
tion of  places  with  respect  to  each  other 
and  to  the  sun  at  the  different  seasons  of 
the  year.  They  are  formed  of  metal  or 
plaster,  on  the  surface  of  which  is  de- 
lineated a  map  of  the  earth,  or  of  the 
celestial  constellations,  together  with  the 
principal  circles  of  the  sphere ;  in  the 
former  case  the  instrument  is  called  a 
terrestrial,  in  the  latter  a  celestial  globe. 
These  globes  are  also  used  for  the  pur- 
pose of  solving  mechanically  a  few  ele- 
mentary problems  of  Astronomy,  relative 
to  the  difference  of  the  hour  of  the  day  at 
different  places,  the  times  of  the  rising 
and  setting  of  the  sun,  the  limits  of  the 
visibility  of  eclipses,  &c. 

2.  Perennial  Globe.  A  contrivance  in 
which  there  is  a  motion  of  the  stars 
about  the  pole  of  the  ecliptic,  and  also 
one  about  the  pole  of  the  equator,  so  that 
all  the  diurnal  phenomena  can  be  repre- 
sented for  any  epoch,  however  distant 
from  our  own,  past  or  future. 

GLOBULAR  CHART.  A  delineation 
of  the  terrestrial  surface,  or  of  any  part  of 
it,  on  a  plane,  according  to  the  principles 
of  globular  projection.    See  Projection. 

GLOBULAR  MASSES.  Nodules.  The 
geological  term  for  rocks  of  irregular 
form,  varying  from  a  foot  to  a  mile  or 
more,  and  imbedded  either  in  a  stratified 
or  a  massive  rock. 

GLOBULAR  SAILING.  In  Naviga- 
tion, the  sailing  from  one  place  to  an- 
other over  an  arc  of  a  great  circle,  or 
the  shortest  distance  between  the  two 
places. 

GLO'BULINE.  The  name  given  by 
Turpin  to  the  amylaceous  granules  found 
in    the   cells    of  plants.    He  considers 


GLU 


GOL 


them  as  the  elementary  form  of  vegetable 
tissue. 

GLOBULUS.  A  little  globe ;  a  round 
deciduous  shield,  formed  of  the  thallus 
of  lichens,  and  leaving  a  cavity  when  it 
falls  off,  as  in  isidium. 

GLO'CHIS  (7\wx«r ,  a  projecting  point). 
A  form  of  hair  occurring  in  plants,  and 
commonly  called  a  barb ;  it  is  forked  at 
the  apex,  both  divisions  of  the  fork,  being 
hooked,  as  in  the  nuts  of  myosotis  lap- 
pula. 

GLOME'RULI  (dim.  of  glomi,  clews 
of  thread).  The  heaps  of  powdery  bodies 
which  lie  upon  the  surface  of  the  thallus 
of  lichens.     See  Soredia. 

GLOMERULUS  or  GLO'MUS.  A 
term  applied,  in  inflorescence,  to  a  clus- 
ter of  capitula  enclosed  in  a  common 
involucre,  as  in  echinops.  It  bears  the 
same  relation  to  a  capitulum  as  the  com- 
pound to  the  simple  umbel. 

GLOSSO'LOGY  {yXwcaa,  a  tongue, 
X670P,  an  account).  The  science  of 
scientific  language ;  the  explanation  of 
the  peculiar  terms  employed  in  any 
science. 

GLOSSOPE'TRA  (yXZaaa,  a  tongue, 
nerpa,  a  rock).  A  term  applied  to  the 
fossil  teeth  of  fishes  allied  to  the  shark, 
occurring  in  the  upper,  secondary,  and 
tertiary  strata  of  England,  France,  &c. 
They  are  also  called  odontopetre,  lamio- 
dontes,  &c. 

GLUCIC  ACID  {yXvKvs,  sweet).  An 
acid  formed  by  the  action  of  a  saturated 
solution  of  lime  or  barytes  on  grape 
sugar.  The  anhydrous  acid  is  formed 
from  grape  sugar  by  the  loss  of  the  ele- 
ments of  water. 

GLUCI'NA  (yXvuvs,  sweet).  A  rare 
earth,  constituting  nearly  14  per  cent,  of 
the  emerald  or  beryl.  Its  metallic  basis 
is  glucinum,  a  metal  named  in  allusion 
to  the  sweet  taste  of  the  salts  of  its  oxide 
glucina. 

GLUCO'SE  (vXuKvf,  sweet).  A  syn- 
onymous term  for  starch  sugar,  diabetic 
sugar,  grape  sugar,  or  the  sugar  of  fruits. 

GLUME  {gluma,  the  husk  of  corn). 
A  term  applied  to  the  peculiar  envelope 
of  the  floral  apparatus  in  grasses,  which 
are  hence  called  glumacece.  It  is  a  modi- 
fication of  the  bract. 

GLUME'LLE.  A  diminutive  of  glume, 
and,  as  such,  applied  by  De  Candolle  to 
each  of  the  bracts  of  grasses,  situated 
immediately  within  the  glumes ;  they  are 
commonly  called  palece.  A  further  di- 
minutive occurs  in  glumellule,  which  the 
same  writer  applies  to  the  minute  hypo- 
153 


gynous  scales  situated  within  the  glu- 
melles  or  paleae,  and  which  are  also  called 
squamulcB. 

GLUTEN  (gelo,  to  congeal).  A  viscid 
substance  obtained  from  wheaten  flour. 
It  has  been  separated  into  gliadine,  or 
vegetable  albumen,  and  zymome,  or  that 
portion  of  the  mass  with  which  the  acid 
that  is  present  has  united.  Glutine  is  a 
principle  resembling  gluten,  but  differing 
from  it  in  not  being  soluble  in  alcohol. 

GLY'CERIN  (jXvkvv,  sweet).  The 
sweet  principle  of  oils,  also  called  hydrate 
of  oxide  of  glyceryl,  the  hypothetical 
radical  of  glycerin. 

GLYTTODON  (yXvirrbs,  sculptured, 
63oi/f,  a  tooth).  A  colossal  armadillo, 
occurring  in  the  geological  period  of  the 
megatheroid  animals,  remarkable  for 
the  complicated  structure  of  its  teeth. 
It  resembled  the  great  land  tortoise, 
whose  remains  are  found  in  the  Sewalik 
hills. 

GNEISS.  A  term  applied  by  the  Ger- 
man miners  to  a  stratified  primary  rock, 
composed  of  the  same  materials  as  gra- 
nite, but  having  usually  a  larger  propor- 
tion of  mica,  and  a  laminated  texture. 
Three  principal  kinds  of  gneiss  have  been 
distinguished — the  granitic,  the  slaty, 
and  the  laminar. 

GNO'MON  {yvcofxav,  a  gnomon).  In 
every  parallelogram,  any  of  the  parallelo- 
grams about  a  diameter,  together  with  the 
complements,  is  called  a  gnomon.  The 
term  gnomon  also  designates  an  upright 
pillar,  from  the  shadow  of  which  the 
ancient  astronomers  determined  the  alti- 
tude of  the  sun  and  of  the  other  heavenly 
bodies.  The  style  or  index  of  a  dial  is 
likewise  termed  a  gnomon. 

GOBEL'S  PYROPHORUS.  A  mix- 
ture of  charcoal  and  lead,  in  which  the 
latter  is  in  such  an  extreme  state  of 
division,  as  to  take  fire  on  exposure  to 
the  air.  It  is  formed  by  heating  the 
tartrate  of  lead  in  a  close  vessel  or  tube 
to  dull  redness. 

GO'BIOD^E  {gobius,  the  goby).  The 
Goby  tribe ;  a  family  of  Acanthopterygious 
fishes,  distinguished  by  the  thinness  and 
flexibility  of  their  dorsal  spines.  Many 
of  them  are  viviparous,  as  the  blenny. 

GOLD.  A  yellow  metal,  occurring 
native,  in  a  massive  state,  and  dissemi- 
nated in  veins  through  rocks,  or  in  grains 
among  the  sand  of  rivers.  Gold  coin  is 
termed  sterling,  when  it  consists  of  22 
parts  of  gold  and  2  of  copper ;  standard, 
when  it  consists  of  18  parts  of  gold  and 
6  of  copper. 

H5 


GON 


GR  A 


GOLD  LEAF  ELECTROMETER. 
An  instrument  for  detecting  the  presence 
of  electricity  by  the  divergence  of  two 
slips  of  gold  leaf. 

GOLDEN  NUMBER.  At  the  end  of 
every  nineteen  years,  the  new  and  full 
moons  happen  at  very  nearly  the  same 
times  of  the  year.  The  ancients  ascer- 
tained this  fact,  and  reckoned  the  nine- 
teen years,  or  "  cycle  of  the  moon,"  as  it 
is  called,  so  that  it  terminated  the  year 
before  the  Christian  era.  This  cycle  was 
marked  by  the  Greeks  with  letters  of 
gold.  Therefore,  to  find  the  golden 
number,  or  number  of  the  year  in  this 
cycle,  add  1  to  the  date ;  divide  by  19 ; 
the  quotient  is  the  number  of  cycles  of 
the  moon  since  the  birth  of  Christ,  and 
the  remainder  is  the  golden  number. 
Thus,  1847  +  1  =  1848.  Divide  by  1 9,  and 
the  quotient  is  97  cycles,  and  5  remain- 
ing, which  is  the  golden  number  for 
1847. 

GOLDEN  SULPHURET.  A  sulphu- 
ret  of  antimony,  also  termed  sulphanti- 
monic  acid,  and  prepared  by  precipitating 
antimonic  acid  by  sulphuretted  hydro- 
gen.    See  Kermes  Mineral. 

GO'MPHOLITE  (yonQot,  a  nail,  X/flo?, 
a  stone).  A  term  applied  by  Brongniart 
to  conglomerate  rocks  of  the  tertiary 
series,  called  by  the  Swiss  Nagelflue. 

GONG.  Tam-tam  of  the  Chinese.  A 
highly  sonorous  species  of  cymbal,  con- 
sisting of  an  alloy  of  about  80  parts  of 
copper  and  20  of  tin. 

GO'NGYLI  (yoyfv\o*t  round).  The 
granules  contained  in  the  shields  of 
lichens,  supposed  to  be  the  spores  by 
which  the  plants  are  propagated.  The 
term  gongylus  is  also  applied  to  a  round 
hard  body,  which  falls  off  from  the 
mother  plant  in  some  of  the  algaceae, 
producing  a  new  individual,  as  in  the 
fuci. 

GO'NIATITES  (ycovia,  an  angle)  The 
name  of  some  spirally  twisted  species  of 
cephalopods  which  inhabited  the  seas 
during  the  Carboniferous  period,  and  are 
characterized  by  the  angular  markings 
made  by  the  intersections  of  the  walls  of 
the  chambers  and  the  outer  shell. 

GONIO'METER.  An  instrument  for 
measuring  angles,  particularly  those  of 
crystals. 

GONIO'METRY  (yoi/m,  an  angle,  Me- 
Tpew,  to  measure).  "  The  measurement 
of  angles ;  a  name  which  should  be  sub- 
stituted for  trigonometry,  if  it  were  ad- 
visable to  alter  established  designations. 
The  latter  science,  beginning  with  the 
154 


measurement  of  triangles,  made  all  that 
was  known  of  the  analysis  of  angular 
magnitude  its  own  peculiar  instrument. 
The  various  accessions  which  real  gonio- 
metry  received  were,  therefore,  consi- 
dered as  additions  to  trigonometry;  so 
that,  at  this  day,  under  a  word  which 
imports  measurement  of  triangles,  we 
have  a  science  which  wanders  as  far 
from  the  etymology  of  its  name  as  geo- 
metry does."— Penny  Cycl. 

GO'NOPHORE  (76vu? ,  offspring,  0<?po>, 
to  bear).  The  name  given  by  De  Can- 
dolle  to  a  prolongation  of  the  receptacle, 
which  elevates  itself  from  the  base  of  the 
calyx  of  certain  flowers,  and  bears  the 
numerous  stamens  peculiar  to  these 
plants,  as  in  Anonacea?  and  Magnoliaceae. 

GO'NOPLA'CIANS  (yuvia,  an  angle, 
?r\a£ ,  a  plate).  A  tribe  of  brachyurous 
crustaceans,  named  from  the  genus  gono- 
plax,  and  characterized  by  the  square  or 
rhomboidal  form  of  the  carapace,  or 
upper  crustaceous  plate,  and  by  the 
length  of  the  eye-stalks.  Some  species 
of  the  gonoplax  are  fossil. 

GORGO'NIA  NOBILIS.  Red  coral; 
a  substance  consisting  of  an  interior 
stem  of  gelatinous  matter  and  carbonate 
of  lime,  and  an  external  coating  of  mem- 
brane, carbonate  of  lime,  and  colouring 
matter. 

GOULARD'S  EXTRACT.  A  satu- 
rated solution  of  subacetate  of  lead,  ob- 
tained by  boiling  powdered  litharge  in 
vinegar. 

GO'VERNOR.  A  piece  of  mechanism 
applied  to  steam-engines  and  other  ma- 
chines, for  the  purpose  of  equalizing 
their  motion. 

GRACULI'NjE  {graculus,  a  jay).  Gra- 
culine  birds,  or  Grackles ;  a  term  adopted 
by  Macgillivray  instead  of  that  of 
Thremmaphilince,  and  applied  to  a  group 
of  birds,  allied  to  the  Crows  on  the  one 
hand,  and  the  Thrushes  on  the  other,  in- 
cluding the  starling,  the  cow-bird,  &c. 
By  several  authors  they  are  called  stur- 
nidcc. 

GRADUATION  {gradus,  a  degree). 
The  process  of  dividing  a  mathematical 
or  astronomical  instrument  into  degrees, 
minutes,  &c,  either  by  copying  a  system 
of  divisions  already  existing,  or  by  origi- 
nal division,  depending  on  the  geometri- 
cal properties  of  the  circle. 

GRADUATOR.  A  contrivance  for 
accelerating  spontaneous  evaporation  by 
exposing  large  surfaces  of  liquids  to  a 
current  of  air.  This  process  of  gradu- 
ation is  sometimes  employed   in    salt 


GRA 


GR  A 


works,  for  the  purpose  of  concentrating 
the  brine,  by  allowing  a  shower  of  it  to 
trickle  over  fagots. 

GRAFTING.  The  horticultural  ope- 
ration by  which  a  portion  of  one  plant  is 
so  applied  to  another  plant  that  a  vital 
union  may  take  place  between  them  ; 
the  portion  so  applied,  is  called  the  scion; 
the  rooted  plant  to  which  it  is  applied,  is 
the  stock  or  stem.  There  are  various 
modes  of  grafting,  which  have  received 
the  names  of  whip,  cleft,  saddle,  and 
crown  grajting. 

Grafting  by  approach,  or  Inarching,  is 
a  mode  of  grafting,  by  which  the  scion  is 
not  separated  from  its  parent  plant,  until 
it  has  become  vitally  united  to  the  stock. 
GRAINER.  The  ley  obtained  by  the 
infusion  of  pigeon's  dung  in  water,  em- 
ployed for  imparting  flexibility  to  skins 
in  the  process  of  tanning. 

GRALLATO'RES  ( grallce,  stilts). 
Waders,  or  Stilt-birds ;  an  order  of  aquatic 
birds  frequenting  marshes,  and  named 
from  their  being  raised  on  their  long  legs, 
as  on  stilts.  They  comprise  the  heron, 
the  snipe  and  woodcock,  the  rail  and 
coot,  and  the  plover. 

GRAMINA'CEjE  {gramen,  grass). 
The  grass  tribe  of  Monocotyledonous 
plants.  Herbaceous  plants  with  cylin- 
drical stems;  leaves  alternate,  with  a 
split  sheath ;  flowers  hermaphrodite, 
sometimes  monoecious,  glumaceous  ; 
glumes  alternate,  unequal;  stamens  hy- 
pogynous ;  ovarium  simple. 

GRAMMAR  (ypan^a,  a  letter).  That 
branch  of  science  which  relates  to  the 
component  parts  of  language,  and  em- 
braces the  subjects  of  orthography,  ety- 
mology, syntax,  and  prosody. 

GRA'NITE  (granum,  a  grain).  An 
unstratified  or  igneous,  coarse,  granular 
rock,  occurring  generally  beneath,  or 
associated  with,  the  oldest  of  the  strati- 
fied rocks,  and  sometimes  penetrating 
them  in  the  form  of  dikes  and  veins.  It 
commonly  consists  of  three  simple  mine- 
rals— quartz,  felspar,  and  mica.  Several 
varieties  of  granite  have  received  dis- 
tinctive names,  as  the  porphyritic,  the 
graphic,  the  schorly,  the  talcose,  and  the 
hornblendic. 

GRANI'VORiE  (granum,  a  grain,  voro, 
to  devour).  An  order  of  birds,  including 
the  Insessores,  which  feed  on  grains. 

GRANULA  (dim.  of  granum,  a  grain). 

Little  grains,  a  term  applied  to  the  large 

sporules  continued  in  the  centre  of  many 

Algaceous  plants. 

GRA'NULATED  (granulatus,  grained). 

153 


Grained  ;  marked  by  elevated,  closely- 
set,  regular  grain-like  dots ;  an  appear- 
ance very  common  at  the  base  of  the 
predacious  spiral  genera  of  mollusca. 

GRANULATION  [granum,  a  grain). 
The  division  of  a  metallic  substance  into 
grains  or  minute  particles,  for  the  pur- 
pose of  facilitating  chemical  combination ; 
it  is  performed  by  pouring  the  metal  into 
water,  or  by  agitating  it  in  a  closed  vessel 
until  the  moment  of  congelation,  when  it 
falls  into  powder. 

GRA'PHIC  GRA'NITE.  A  modifi- 
cation of  granite,  which  derives  its  name 
from  its  presenting,  when  polished,  some 
appearance  of  written  characters.  See 
Granite. 

GRAPHIC  ORE  or  GOLD.  An  ore 
of  tellurium,  occurring  in  veins  in  por- 
phyry, in  Transylvania,  and  consisting  of 
tellurium,  gold,  and  silver. 

GRAPHITE  (7pa0w,  to  write).  Plum- 
bago or  black-lead ;  a  carburet  of  iron, 
named  from  its  use  in  writing.  Compact 
graphite  occurs  at  Borrowdale  in  Cum- 
berland, in  beds  of  variable  thickness, 
included  in  a  bed  of  trap,  which  is  sub- 
ordinate to  clay-slate.  Artificial  graphite 
is  produced  by  placing  an  excess  of  char- 
coal in  contact  with  fused  cast  iron. 

GRAPSOIDIANS.  A  tribe  of  bra- 
chyurous  crustaceans,  named  from  the 
genus  grapsus,  and  placed  by  M.  Milne 
Edwards,  near  the  Gonoplacians. 

GRA'PTOLITE  (ipanrd?,  written, 
\»0oc,  a  stone).  A  fossil  sertularian  co- 
ralline, one  of  the  most  simply  organized 
of  the  Silurian  species,  consisting  appa- 
rently of  the  horny  skeletons  of  animals 
resembling  those  found  on  the  coral  and 
sea- weed  of  our  own  coast.  By  this  term 
Linnaeus  designated  those  stones  which 
are  marked  with  various  forms,  repre- 
senting buildings,  vegetable  structures, 
as  ruin  marble,  moss-agate,  &c. 

GRAVPMETER  (gravis,  heavy,  p.e- 
rpov,  a  measure).  An  unclassical  term, 
adopted  by  M.  Greyton  in  preference  to 
hydrometer  or  araeometer,  because  these 
terms  imply  that  the  substance  weighed 
is  a  liquid,  whereas,  when  solids  are 
weighed,  the  liquid  is  only  the  term  of 
comparison  to  which  the  unknown  weight 
is  referred. 

GRAVITA'TION  (gravitas,  weight). 
This  term  has  been  sufficiently  explained 
under  the  head  of  Attraction.  The  laws 
of  gravitation,  as  laid  down  by  Newton, 
and  universally  admitted,  are  as  follows  : 
— The  gravitating  forces  of  bodies  are  to 
each  other,  1,  directly  as  their  masses  • 
H6 


GRE 


GRO 


and  2,  inversely  as  the  squares  of  their 
distances.  Thus,  if  the  mass  of  one  body 
be  2,  3,  4,  or  5  times  greater  than  that  of 
another,  its  gravity  is  also  2,  3,  4,  or  5 
times  greater;  and  with  a  distance  of 
2,  3,  4,  or  5  times  greater,  the  force  of 
gravity  will  be  4,  9,  16,  or  25  times  less. 

GRAVITY  (gravitas,  heaviness).  A 
name  given,  in  Physics,  to  the  tendency 
which  all  bodies  have  to  the  centre  of 
the  earth.  The  term  is  often  used  syno- 
nymously with  attraction,  from  which, 
however,  it  differs  as  a  species  from  a 
genus :  we  speak,  for  instance,  of  capil- 
lary attraction  and  of  magnetic  attrac- 
tion, but  not  of  capillary  or  magnetic 
gravity. 

1.  Gravity,  specific.  The  density  of 
bodies,  as  ascertained  by  comparison  with 
an  equal  bulk  of  water,  which  is  assumed 
as  unity,  or  the  absolute  weight.  One 
substance  is  said  to  have  a  greater  specific 
gravity  than  another,  when  a  less  portion 
of  its  bulk  is  of  equal  weight  to  that  other. 
Thus,  a  cubic  inch  of  platinum  is  nearly 
twice  as  heavy  as  a  cubic  inch  of  silver ; 
the  specific  gravity  of  the  former  is, 
therefore,  double  that  of  the  latter. 

2.  Gravity,  centre  of.  That  point  in  a 
body,  about  which  all  its  parts,  in  any 
situation,  balance  one  another.  Hence 
if  the  body  could  be  suspended  from  this 
point,  it  would  remain  at  rest,  with  re- 
ference to  its  tendency  towards  the  earth, 
in  whatever  respective  position  the  sur- 
rounding parts  may  be  turned.  Thus, 
the  centre  of  gravity  of  a  globe,  if  of  uni- 
form density,  is  its  common  centre,  and 
that  of  a  balanced  beam  is  the  pivot  on 
which  it  turns. 

3.  Gravity,  line  of  direction  of.  That 
line  which  passes  through  the  centre  of 
gravity  of  a  body  in  a  direction  to  the 
centre  of  the  earth. 

GRAYSTONE.  A  term  suggested  for 
designating  certain  volcanic  rocks  com- 
posed of  felspar,  augite,  or  hornblende, 
and  iron;  the  felspar  being  sometimes 
replaced  by  leucite  or  melilite. 

GREEK  FIRE.  An  explosive  sub- 
stance, invented  by  the  Greeks,  supposed 
to  consist  of  asphaltum,  nitre,  and  sul- 
phur. 

GREEN  EARTH.  An  earthy  or  granu- 
lar variety  of  chlorite,  which  occurs  mas- 
sive, dispersed  in  rocks,  or  enclosed  in 
some  simple  minerals,  as  rock-crystal, 
and  often  in  the  globular  cavities  of  cer- 
tain rocks.  It  is  the  mountain  green  of 
artists  in  water  colours. 

GREEN  MINERAL.  A  carbonate  of 
156 


copper,  employed  as  a  pigment.  Scheele's 
green  is  an  arsenite  of  copper;  Bruns- 
wick green,  an  oxychloride  of  copper. 

GREENSAND.  A  designation  of  beds 
of  sand,  sandstone,  and  limestone,  be- 
longing to  the  Cretaceous  Period.  They 
are  so  named  from  the  abundance  of 
green  earth  or  chlorite  which  is  often 
scattered  through  their  substance. 

GREENSTONE.  A  variety  of  trap, 
consisting  of  hornblende  and  felspar,  in 
nearly  equal  proportions,  and  having  a 
granitic  structure.  The  name  is  not  very 
appropriate,  for,  besides  being  sometimes 
greenish,  it  is  not  uncommonly  reddish 
or  whitish,  the  colour  depending  chiefly 
on  that  of  the  felspar,  which  is  generally 
compact,  or  at  least  not  highly  crystalline. 
This  rock  is  called  diabase  by  the  French 
geologists,  who  name  the  compact  green- 
stone aphanite. 

GREGORIAN  TELESCOPE.  A  re- 
flecting telescope,  having  a  hole  in  the 
centre  of  the  great  speculum,  through 
which  the  image  is  thrown  by  the 
small  reflector  to  the  eye.  The  dis- 
tinctness of  the  object  seen  through 
this  telescope  is  somewhat  diminished 
by  the  hole  in  the  great  speculum. 

GRENATITE.  Staurotide.  A  desig- 
nation of  the  prismatic  garnet. 

GREYWACKE'  {grau,  grey,  wacke,  a 
provincial  miner's  term).  A  German 
designation  of  some  of  the  most  common 
fossiliferous  strata,  consisting  of  a  series 
of  arenaceous  and  slaty  rocks,  of  evidently 
mechanical  origin,  intermixed  with  small 
beds  of  limestone.  The  rocks  are  very 
often  of  a  grey  colour. 

GRIDIRON  PENDULUM.  Harri- 
son's compensation  pendulum,  which  is 
constructed  of  different  substances,  so 
combined  that  the  effects  of  heat  coun- 
teract each  other,  and  the  length  of  the 
rod  remains  unaltered. 

GRIT.  A  provincial  name  for  a  coarse- 
grained sandstone,  employed  for  mill- 
stones, &c.  Calcareous  grit,  or  sandstone, 
is  one  of  the  subdivisions  of  the  Middle 
Oolite  Formation. 

GROSSIFICA'TION.  A  term  applied 
to  the  swelling  of  the  ovary  of  plants 
after  fertilization. 

GRO'SSULAIRE.  A  green  crystal- 
lized mineral,  found  imbedded  with  ve- 
suvian,  in  a  pale  greenish-grey  claystone 
in  Siberia. 

GROTTO  DEL  CANE.  The  Dog'a 
Grotto  ;  a  cave  in  Italy,  in  which  there  is 
a  constant  natural  exhalation  of  carbonic 
acid  gas,  which,  occupying  the   lowest 


GUL 


GYM 


stratum  of  the  air,  causes  asphyxia  in 
animals  introduced  into  it. 

GROUND  BASE.  In  Music,  a  base/ 
consisting  of  a  very  few  bars,  which  are! 
continually  repeated  during  the  wholel 
movement. 

GRU'IDjE  {grus,  a  crane).  A  family 
of  wading  birds,  named  from  the  genus 
grus. 

GRUMOUS  (grumus,  a  clot).  Knotted ; 
collected  into  granular  masses,  as  the 
fecula  in  the  stem  of  the  Sago  palm. 

GRUS.  The  Crane  ;  a  southern 
constellation  consisting  of  fourteen 
stars. 

GRY'LLIDjE  {gryllus,  a  grasshopper). 
The  Grasshopper  tribe ;  a  group  of  or- 
thopterous  insects,  belonging  to  the  tribe 
saltatoria,  and  distinguished  by  the  roof- 
like position  of  the  elytra,  or  wing-cases, 
when  these  are  closed. 

GRYPHjE'A.  A  genus  of  bivalves, 
allied  to  the  oyster,  and  found  abundantly 
in  the  secondary  strata  of  Europe  from 
the  lias  upwards  to  the  chalk,  but  scarcely 
known  in  the  tertiary  strata. 

GRY'PHITE  LIMESTONE.  A  de- 
signation of  the  Lias  formation,  from  the 
numerous  shells  of  the  genus  gryphcea 
which  it  contains. 

GUANO.  A  manure  employed  in 
South  America,  consisting  of  urate  of 
ammonia  and  other  ammoniacal  salts. 
It  appears  to  consist  of  the  excrements 
of  sea- fowl. 

GUIA'NA  CURRENT.  A  branch,  or 
rather  a  continuation,  of  the  great  equa- 
torial current,  running  from  Cape  St. 
Roque  in  Brazil  to  the  Island  of  Trini- 
dad, along  the  low  co^st  of  Guiana,  and 
at  no  great  distance  from  it,  and  lost  in 
the  Caribbean  sea.  Its  whole  course  ex- 
tends to  about  2500  nautical  miles.  See 
Brazil  Current. 

GUINEA,  or  NORTH  AFRICAN 
CURRENT.  A  current  in  the  North 
Atlantic,  which  has  its  origin  in  the  sea 
between  the  southern  coast  of  Ireland 
and  Cape  Finisterre  in  Spain,  and  ranges 
along  the  coast  of  Guinea.  Near  its  ori- 
gin, a  branch,  called  RennelVs  Current, 
separates  itself  from  the  main  stream, 
and  performs  a  complete  rotation  be- 
tween Spain,  France,  and  the  Atlantic 
at  large. 

GULF.  A  portion  of  the  ocean  running 
up  into  the  land  between  two  promon- 
tories, and  spreading  out  info  a  capacious 
bay.  A  bay  (bow)  is  a  projection  of  the 
ocean  into  the  land,  but  is  not  necessarily 
a  gulf,  which  includes  the  idea  of  a  sort 
157 


of  abyss  where  the  waters  are  engulfed, 
or  swallowed  up. 

GULF  STREAM.  The  name  given 
by  navigators  to  that  current  of  the 
Atlantic,  which  traverses  the  sea  between 
the  parallels  of  36°  and  44°  in  the  northern 
hemisphere.  It  enters  the  gulf  of  Mexico, 
through  the  strait  formed  by  the  western 
end  of  Cuba  and  the  opposite  peninsula, 
follows  the  bendings  of  the  Mexican 
coast,  and  flows  into  the  gulf  of  Florida. 
~*GUM.   "Vegetable    mucilage;   a  com- 


I 


mon  proximate  principle  of  plants.  Gum- 
resins  are  the  concrete  juices  of  certain 
plants,  consisting  of  resin,  gum,  essential 
oil,  and  extractive  matter. 

GUNPOWDER.  An  explosive  mix- 
ture of  five  parts  of  nitre,  one  of  sulphur, 
and  one  of  charcoal,  finely  powdered,  and 
very  accurately  blended.  The  grains  are 
smoothed  by  friction,  and  are  then  said 
to  be  glazed. 

GUNTER'S  LINE.  A  logarithmic 
line  engraved  on  scales,  sectors,  &c,  for 
facilitating  the  multiplication  and  divi- 
sion of  numbers.  The  numbers  are 
usually  drawn  upon  two  separate  rules, 
which  slide  against  each  other.  See  Scale. 

GURHO'FFITE.  Compact  dolomite, 
occurring  in  serpentine  rocks  in  Lower 
Austria. 

GUTTA  PERCHA.  A  substance  con- 
tained in  the  sap  of  a  tree  belonging  to 
the  natural  order  Sapotacece,  abounding 
in  the  island  of  Singapore  and  in  the 
Malayan  peninsula.  It  is  plentiful  in 
Sarawak,  where  it  is  called  Niato,  and  is 
probably  to  be  found  over  the  whole 
island  of  Borneo.  The  substance,  as  an 
article  of  commerce,  appears  likely  to 
rival  caoutchouc  in  its  application  to  the 
useful  and  ornamental  arts. 

GUTTIFERjE  (gutta,  a  drop,  fero,  to 
bear).  The  Mangosteen  tribe  of  Dico- 
tyledonous plants.  Trees  or  shrubs,  oc- 
casionally parasitical,  yielding  resinous 
juice;  leaves  entire,  opposite;  flowers 
polypetalous  ;  stamens  hypogynous  ;  car- 
pels concrete  ;  ovary  consisting  of  several 
cells. 

GYMNOCA'RPOUS  (yvfxvor,  naked, 
Kap7r6?.  fruit).  A  term  applied  to  a  class 
of  fruits  in  the  arrangement  of  Mirbel, 
in  which  the  fruit  is  not  disguised  by  the 
adherence  of  any  other  organ  than  the 
calyx.     See  Angeiocarpous. 

GYMNODO'NTES  (71/^69,  naked, 
b&ovs,  a  tooth).  A  family  of  the  plecto- 
gnathous  fishes,  including  the  spinous 
globe-fishes,  in  which  the  jaws  are  co- 
vered with  a  substance  resembling  ivory, 


H  AB 


H.EM 


arranged  in  small  plates,  representing 
united  teeth.  These  plates  are  repro- 
duced as  soon  as  destroyed  by  use. 

GY'MNOSPERMS  (jappfe,  naked, 
cnrtpfia,  seed).  A  class  of  plants  which 
agree  in  all  respects  with  Exogens,  ex- 
cept that  their  ovules,  instead  of  being 
enclosed  in  a  pericarp,  are  exposed  naked 
to  the  fertilizing  influence  of  the  pollen, 
as  in  the  Coniferae  and  the  Cycadaceae. 
See  Angeiospermia. 

GYNjECE'UM  {ywaiKelov,  the  wo- 
man's part  of  the  house).  A  term  ap- 
plied by  Roper  to  the  entire  female  sys- 
tem of  plants,  with  reference  to  the  fan- 
ciful language  of  Linnaeus.  It  is  com- 
monly called  the  pistil,  and  comprises 
the  ovary,  the  style,  and  the  stigma.  See 
Androceum. 

GYNA'NDRIA  {yvvrj,  a  woman,  uvrjp,  a 
man).  The  twentieth  class  in  the  Lin- 
naean  system  of  plants,  in  which  the 
stamens  are  situated  upon  the  style, 
above  the  ovary,  as  in  passiflora. 

GY'NOBASE  (ywrj,  a  woman,  fidotr, 
a  base).  A  term  applied  to  the  recep- 
tacle in  plants,  when  it  is  dilated  and 
supports  a  row  of  carpels,  which  have  an 
oblique  inclination  towards  the  axis  of  the 
flower,  as  in  Labiatae,  Boraginaceae,  &c. 

GY'NOPHORE  (-yut/^,  a  woman,  <pePa>, 
to  bear).  Thecaphore.  A  term  applied, 
in  Botany,  to  the  stalk  upon  which  the 
ovary  is  sometimes  seated,  instead  of 
being  sessile,  as  in  taesonia. 

GYNOSTE'MIUM  (ywtj,  a  woman, 
(rrrjuuiv,  a  stamen).  A  term  applied  by 
Richard  to  that  condition  of  the  filaments 
in  Orchidaceae,  in  which  they  are  com- 
bined into  a  solid  body  called  the 
columna. 

GY'PSUM  (71^0?,  chalk;  from  yn, 
earth,  e^o>,  to  bake).    Sulphate  of  lime; 


a  modification  of  limestone,  with  a  granu- 
lar or  crystalline  texture,  forming  beds 
and  irregular  masses,  and,  when  highly 
burned,  constituting  plaster  of  Paris. 
There  are  two  species,  according  to 
Jameson,— the  prismatic,  and  the  axi- 
frangible. 

GY'RATE  (7i;po9,  curved).  Curved 
in  from  apex  to  base,  as  the  fronds  of 
ferns;  a  term  synonymous  with  circi- 
nate. 

GYRA'TION  (gyrus,  a  circle).  The 
act  of  turning  round  a  centre,  in  the 
manner  of  a  wheel.  The  centre  of  gyra- 
tion is  that  point  in  a  revolving  body, 
into  which,  if  all  its  matter  could  be  col- 
lected, it  would  continue  to  revolve  with 
the  same  energy  as  when  its  parts  were 
in  their  original  places. 

Gyration,  circle  of.  A  wheel  in 
motion  may  be  considered  as  an  indefi- 
nite number  of  pendulums,  each  of  which 
has  its  own  centre  of  oscillation.  If  the 
wheel  be  nearly  balanced,  these  several 
points  of  oscillation  will  accommodate 
themselves  so  as  to  form,  in  their  con- 
tinued motion,  a  set  of  points  equally 
distant  from  the  rim.  These  are  centres 
of  gyration,  and  in  their  junction  they 
will  form  a  circle  of  gyration. 

GYRO'GONITE  (yvpos,  curved,  yo^, 
seed).  A  term  applied  to  the  fossil  seed- 
vessel  of  plants  of  the  genus  Chara,  found 
in  fresh-water  deposits.  The  name  was 
derived  from  the  idea  that  they  were 
shells  of  polythalamous  cephalopods. 

GYRO'MA  (71/poc,  curved).  Gyrus. 
A  term  sometimes  used  as  synonymous 
with  the  annulus  of  the  theca  of  ferns. 
It  is  also  applied  to  the  shield,  or  trica, 
of  lichens,  the  surface  of  which  is  covered 
with  sinuous  concentric  furrows. 


H 


HAA'RKIES  (haar,  German,  hair). 
A  designation  of  capillary  pyrites  occur- 
ing  in  very  delicate  acicular  crystals. 
The  term  is  also  applied  by  German 
mineralogists  to  a  native  sulphuret  of 
nickel. 

HABITATION.  A  technical  term  em- 
ployed in  botany  to  indicate  generally  the 
country  where  a  plant  grows  wild.  It 
must  be  distinguished  from  the  term 
station.  The  study  of  stations  has  been 
styled  the  topography,  that  of  habitations 
158 


the  geography,  of  botany.  Thus,  the 
station  of  a  plant  may  be  a  salt-marsh, 
in  a  temperate  climate,  a  hill-side,  the 
bed  of  the  sea,  or  a  stagnant  pool.  Its 
habitation  may  be  Europe,  North  Ame- 
rica, or  New  Holland  between  the  tropics. 
See  Station. 

HEMATITE  {oJ/jLa,  blood).  Blood- 
stone ;  a  native  oxide  of  iron,  so  named 
from  its  blood-red  streak.  The  red 
haematite  is  an  anhydrous,  the  brown  a 
hydrated,  peroxide. 


HAL 


HAR 


HAIDI'NGERITE.  An  ore  of  anti- 
mony, consisting  of  sulphuret  of  anti- 
mony and  protosulphuret  of  iron. 

HAIL.  Drop3  of  rain,  more  or  less 
suddenly  frozen  by  exposure  to  a  tempe- 
rature below  32°.  They  assume  various 
figures,  being  sometimes  round,  at  other 
times  pyramidal,  cuneated,  angular,  thin 
and  flat,  and  sometimes  stellated  with 
six  radii  like  the  small  crystals  of  snow. 
Hail  occurs  only  in  summer  or  in  warm 
climates,  and  when  the  sun  is  above  the 
horizon. 

HAIRS  OF  PLANTS.  Minute  fila- 
mentous processes  found  on  the  cuticle 
and  in  certain  cavities  of  plants,  consist- 
ing of  elongated  cellular  tissue,  and  con- 
stituting, in  the  cotton  plant,  the  pecu- 
liar substance  which  envelopes  the  seeds, 
and  is  manufactured  into  linen.  The 
variable  qualities  of  hairs  have  given 
rise  to  various  designations,  as  pilosity, 
villosity,  pubescence,  velvet,  bristles, 
stings,  glandular  hairs,  hooks,  barbs,  &c. 
Hairy  surfaces  are  also  named,  with 
reference  to  the  quality  and  form  of  the 
hairs,  silky,  arachnoid,  manicate,  bearded, 
rough,  and  stellate  or  starry. 

HA'LCYON  DAYS  {halcyon,  the  king- 
fisher). Originally,  the  seven  days  which 
precede  and  follow  the  winter  solstice, 
the  period  of  incubation  of  the  halcyon, 
generally  remarkable  for  calm  weather. 
Hence  the  term  denotes  generally  days  of 
calmness. 

HALCYO'NID.E.  AlcedincB.  The 
King-fishers  ;  a  family  of  the  Insessores, 
or  Perching  birds,  remarkable  for  the 
great  length  of  their  bill,  and  the  extreme 
shortness  of  their  feet.  They  feed  upon 
small  fishes  and  insects.  See  Fissi- 
rostres. 

HALIO'TID^l  (a\c,  the  sea,  oSj,  the 
ear).  Ear-shells  ;  a  family  of  the  phyto- 
phagous Gasteropods,  named  from  the 
genus  haliotis,  and  known  by  their  flat, 
ear-shaped  shells,  having  only  the  rudi- 
ment of  a  spire,  and  without  any  pillar ; 
hence  they  may  be  even  called  turbi- 
nated or  spiral  limpets. 

HALISPO'NGIA.  The  generic  type 
of  a  group  of  sponges,  characterized  by 
the  presence  of  siliceous  spiculae,  and 
thus  distinguished  from  the  calcispongia, 
which  contains  calcareous  spiculae,  and 
from  spongia,  which  is  of  a  horny  tubular 
structure. 

HALLEY'S  COMET.  A  comet  named 
from  Edmund  Halley,  who  in  1682  pre- 
dicted its  return  in  1759  :    the  event  co- 
inciding with  the  prediction,  this  comet 
159 


was  first  proved  to  belong  to  the  solar 
system,  and  to  perform  its  revolution  in 
75  or  76  years. 

HA'LO  (a\wf,  an  area).  A  meteor  in 
the  form  of  a  luminous  ring,  of  various 
colours,  appearing  round  the  bodies  of 
the  sun,  moon,  or  stars.     See  Parhelion. 

HA'LOGENE  (a\r,  salt,  7e»/vaa>,  to 
produce).  A  term  employed  by  Berze- 
lius  to  denote  bodies  which  form  salts 
with  metals,  as  chlorine,  bromine,  iodine, 
fluorine,  and  cyanogen.  The  salts  thus 
produced  are  called  haloids. 

HALOID  SALTS  (&Xt,  the  sea,  sea- 
salt,  eidor,  likeness).  Salt-like  com- 
pounds, consisting  of  a  metal  on  the  one 
hand,  and  of  chlorine,  iodine,  and  the 
radicals  of  the  hydracids  in  general, 
excepting  sulphur,  on  the  other.  Be- 
sides the  simple  haloid  salts,  Berzelius 
distinguishes  the  three  following  com- 
binations : — 

1.  Hydro-haloid  Salts,  or  combinations 
of  a  simple  haloid  salt  and  the  hydracid 
of  its  radical. 

2.  Oxy-haloid  Salts,  or  combinations  of 
a  metallic  oxide  with  a  haloid  salt  of  the 
same  metal. 

3.  Double  Haloid  Salts,  consisting, 
1.  of  two  simple  haloid  salts,  which  con- 
tain different  metals,  but  the  same  non- 
metallic  ingredient ;  2.  of  two  haloid 
salts  consisting  of  the  same  metal,  but  in 
which  the  other  element  is  different ; 
and,  3.  of  two  simple  haloid  salts,  of 
which  both  elements  are  entirely  dif- 
ferent. 

HA'MITE  {'dfxt],  hamus,  a  reaping- 
hook).  A  genus  of  fossil  cephalopods, 
with  chambered  shells  bent  in  the  form 
of  a  hook  or  siphon,  with  parallel  but 
unequal  limbs  and  sinuous  septa,  occur- 
ring in  the  gait,  greensand,  and  other 
cretaceous  beds. 

HARDNESS  OF  MINERALS.  The 
comparative  hardness  of  minerals  is 
tested  by  reference  to  a  scale  of  sub- 
stances formed  by  Mohs.  The  hardness 
of  a  mineral  which  neither  scratches  nor 
is  scratched  by  any  particular  substance 
in  this  scale,  is  expressed  by  the  number 
prefixed  to  that  substance.  They  are 
1,  talc;  2,  rock  salt;  3,  calcareous  spar; 
4,  fluor  spar;  5,  apatite;  6,  adularia; 
7,  rock  crystal;  8,  topaz;  9,  corundum; 
10,  diamond.  The  hardness  of  minerals 
is  also  tested  by  the  application  of  a  file. 

Hardness  of  Rocks.  This  character 
does  not  require  so  precise  a  determina- 
tion as  in  the  case  of  simple  minerals. 
The  extremes  are  the  hardness  of  quartz 


HAS 


HE  A 


on  the  one  hand,  and  soft  chalk  on  the 
other. 

HARMO'NICON,  CHEMICAL.  An 
apparatus  for  imparting  a  sonorous  pro- 
perty to  the  air.  If  a  small  flame  of  hy- 
drogen gas  be  made  to  burn  in  a  tube  of 
glass  or  of  any  other  material,  of  from 
one  to  three  inches  in  width,  the  column 
of  air  contained  in  the  tube  will  in  a 
short  time  be  heard  to  give  forth  musical 
sounds.  These  are  occasioned  by  the 
combustion  of  the  hydrogen  in  the  atmo- 
spheric air  contained  in  the  tube,  and 
thus  an  influx  of  the  surrounding  atmo- 
sphere is  produced.  The  sounds  are 
heard  when  the  flame  of  the  hydrogen 
becomes  small  and  steady. 

HARMO'NICS  (apuovla,  concord). 
The  doctrine  of  harmonical  combinations 
in  music,  as  they  occur  in  the  natural 
series,  I,  2,  3,  4,  &c.  Thus,  the  first 
interval,  1  I  2,  is  an  octave ;  the  second, 
1  I  3,  is  a  twelfth ;  the  third,  1  I  4,  is  a 
fifteenth;  the  fourth,  1  ;  5,  a  seven- 
teenth ;  the  fifth,  1  I  6,  a  nineteenth; 
&c. 

HA'RMONY  (apfjLovla,  concord).  A 
combination  of  sounds,  forming  a  mu- 
sical chord,  or  a  succession  of  chords. 
The  harmonic  triad,  or  common  chord, 
consists  of  a  note,  with  its  third  and 
perfect  fifth,  and  is  the  result  of  the 
vibration  of  all  sonorous  bodies. 

HA'RMOTOME  {ap/sos,  a  joint,  to/u»j, 
a  section).  A  silicate  of  barytes  and 
alumina,  containing  water,  found  at  An- 
dreasberg  in  the  Hartz :  the  crystals  of 
this  mineral  intersect  one  another  length- 
wise, and  are  easily  separable.  It  is  also 
called  staurolite,  or  cross  stone. 

HARPA'LlD^i  A  family  of  Coleo- 
pterous insects  of  the  section  Geodephaga, 
named  from  the  genus  Harpalus,  dis- 
tinguished by  the  tarsi  of  the  two  ante- 
rior pairs  of  legs  being  dilated  in  the 
male  sex. 

HARVEST  and  HUNTERS'  MOON. 
Twice  in  the  year  the  moon  rises  almost 
at  the  same  hour  during  a  week.  This 
occurs  in  September  or  October,  and  in 
March  or  April :  in  the  former  case  the 
moon  is  termed  the  harvest  moon,  in  the 
latter  the  hunters'  moon. 

HA'STATE  (hastatus,  spear-shaped). 
A  term  applied,  in  Botany,  to  leaves 
which  have  three  lance-shaped  lobes, 
one  in  the  direction  of  the  midrib,  the 
other  two  at  the  base,  at  right  angles  to 
the  first,  as  in  arum  maculatum. 

HASTINGS  SAND.  The  middle 
group  of  the  Wealden  formation,  consti- 
160 


tuting  the  uppermost  part  of  the  Oolitic 
system  in  England,  and  occurring  around 
Hastings  in  Sussex.  It  consists  of  yel- 
lowish grains  of  sand,  very  loosely  cohe- 
rent, alternating  with  beds  of  clay  and 
conglomerate,  containing  fragments  of 
bones  and  scales  of  fishes. 

HA'TCHETINE.  Mineral  adipocire. 
A  wax-like  substance  occurring  in  the 
nodules  of  iron-stone  in  South  Wales, 
and  named  after  Mr.  Hatchett. 

HAUSMA'NNITE.  A  designation  of 
pyramidal  manganese  ore. 

HAUSTELLA'TA  {haustellium,  a  pro- 
boscis). Haustellate  insects  ;  a  group  in 
which  the  mouth  is  furnished  with  a 
haustellium,  or  proboscis,  adapted  for 
suction.  This  division  includes  the 
homopterous,  heteropterous,  lepidopte- 
rous,  and  dipterous  insects.  See  Mandi- 
bulata. 

HAUYNE.  Latialite.  A  blue  mine- 
ral, occurring  in  basalt  or  lava,  and 
named  from  the  mineralogist  Haiiy. 

HAY'TORITE.  A  variety  of  rhom- 
boidal  quartz,  containing  0*5  per  cent,  of 
oxide  of  iron. 

HEADLAND.  Any  projection  of  the 
land  into  the  sea.  Thus,  a  cape  is  a 
headland,  and  is  distinguished  in  each 
case  by  a  particular  designation  ;  a  pro- 
montory is  also  a  headland,  but,  in  ac- 
cordance with  its  Latin  derivation,  is 
applied  only  when  the  projecting  head  is 
a  high  point  or  a  rock. 

HEART-WHEEL.  A  mechanical  con- 
trivance employed  in  cotton  mills  for 
converting  a  circular  into  an  alternating 
rectilinear  motion.  It  consists  of  a  re- 
volving ellipse,  on  the  edge  of  which  a 
moveable  point  or  circle  presses  ;  the 
latter  receives  an  alternating  motion 
from  the  circumference  of  the  ellipse, 
which  in  its  revolution  presses  it  to  dif- 
ferent distances  from  the  centre  of  mo- 
tion. 

HEART-WOOD.  The  popular  name 
for  the  hard  interior  portion  of  the  stem 
and  branches  of  exogenous  trees,  as  dis- 
tinguished from  sap-wood,  or  the  exterior 
and  softer  portion.  In  botany  the  former 
is  termed  duramen,  the  latter  alburnum. 

H  EAT.  In  popular  language,  the  sen- 
sation experienced  on  touching  a  body  of 
a  higher  temperature  than  that  of  the 
blood.  In  chemical  language,  it  is  the 
cause  of  that  sensation,  or  caloric,  a  term 
by  which  philosophers  distinguish  the 
matter  of  heat  from  its  effect. 

HEAVY  SPAR.  Another  name  for 
baryta,  the  heaviest  of  all  the  earths. 


HEL 

This  genus  has  been  distinguished  into 
four  species;  viz.  1.  the  rhomboidal  or 
witherite,  which  is  a  carbonate  of  baryta, 
occurring  in  lead  veins  ;  2.  the  prismatic, 
or  heavy  spar,  or  sulphate  of  baryta, 
found  in  primitive  and  transition  rocks, 
in  secondary  limestone,  and  in  lead 
mines  ;  3.  the  di-prismatic  or  strontianite, 
a  carbonate  of  strontia  occurring  in 
veins  which  traverse  gneiss ;  and  4.  the 
axifrangible  or  celestine,  a  sulphate  of 
strontia,  occurring  in  trap-tuff  and  in  red 
sandstone. 

HEDENBER'GITE.  A  variety  of 
augite,  of  a  dark-green  colour,  sometimes 
nearly  black:  it  resembles  those  horn- 
blendes in  which  iron  prevails,  and  is 
found  in  Sweden. 

HE'DYPHAN.  A  phosphate  of  lime, 
in  which  a  portion  of  phosphoric  acid  is 
replaced  by  arsenic  acid. 

HE'GIRA.  This  mode  of  computing 
time  among  the  Mahomedans  has  been 
noticed  under  the  article  Era.  It  may 
here  be  added,  that  the  years  of  the 
Hegira  are  divided  into  cycles  of  thirty 
years,  nineteen  of  which  are  termed 
common  years,  of  354  days  each,  and  the 
other  eleven  are  called  intercalary,  or 
abundant,  from  their  consisting  of  one 
day  more.  To  reduce  the  Christian  era 
to  the  Mahomedan,  subtract  622  from  the 
current  year ;  multiply  by  1  0307 ;  cut 
off  four  decimals,  and  add  *46 :  the  sum 
will  be  the  year  and  decimal  of  the  day, 
Old  Style. 

HEIGHT.  This  term,  in  Geometry, 
is  synonymous  with  altitude,  and  denotes 
the  perpendicular  let  fall  from  the  ver- 
tex, or  top,  of  any  rectilinear  figure,  upon 
the  base  or  side  subtending  it.  It  also 
represents  the  position  of  any  object,  in  a 
vertical  direction  above  the  horizon. 

The  measurement  of  heights  is  gene- 
rally effected  by  observing  the  differences 
of  atmospheric  pressure  as  indicated  by 
the  barometer.  In  1815,  Capt.  Smith 
ascertained,  trigonometrically,  that  the 
height  of  Etna  was  10,874  feet.  In 
1824,  Sir  J.  Herschel  determined,  by 
barometrical  measurement,  that  the 
height  was  10,872^  feet.  This  singular 
agreement  of  results,  so  differently  ob- 
tained, was  spoken  of  by  Herschel  as  "a 
happy  accident;"  but  Wollaston  re- 
marked that  "  it  was  one  of  those  acci- 
dents which  would  not  have  happened  to 
two  fools." 

HE'LIACAL  (iiXto?,  the  sun).  A  term 
applied  to  the  rising  and  setting  of  a 
star,  when  it  rises  in  the  morning  a  little 
161 


HEL 

f  before  the  sun,  or  sets  in  the  evening  a 
j  little  after  him.  It  is  only  in  his  heliacal 
rising  and  setting  that  the  planet  Mer- 
cury is  ever  visible  to  the  naked  eye.  See 
Cosmical. 

HELIANTHOI'DA  {helianlhus,  the 
sun-flower,  eidov,  likeness).  An  order  of 
the  polypipherous  Radiata,  named  from 
their  resemblance,  when  expanded,  to 
the  sun-flower.  They  are  also  termed 
actiniform  polyps,  from  their  general 
resemblance  to  the  sea-anemone. 

HELFCIDjE  {helix,  a  snail).  Snails  j 
a  family  of  phytophagous  Gasteropods ; 
these  are  pulmonary  animals,  breathing 
by  a  lateral  opening ;  the  shell  is  light, 
turbinated,  or  spiral ;  the  aperture  al- 
ways entire,  rarely  closed  by  an  opercu- 
lum, and  sometimes  only  rudimentary. 

HELI'CINiE.  Common  Land  Snails ; 
a  sub-family  of  the  Helicidcc,  having 
perfect  turbinated  shells  more  or  less 
depressed;  the  aperture  entire,  but 
without  teeth. 

HE'LICOID  (e\t?,  a  helix,  e'ibo?,  like- 
ness). Parabolic  spiral.  In  Geometry, 
a  curve  generated  by  the  bending  of  the 
axis  of  the  common  parabola  into  the 
circumference  of  a  circle,  the  ordinates 
still  retaining  their  places  and  perpendi- 
cular positions  with  respect  to  the  circle, 
all  these  lines  still  remaining  in  the  same 
plane.  The  equation  of  this  curve  re- 
mains the  same  as  when  it  was  a  para- 
bola. 

HE'LIOCE'NTRIC  (Jj\<of,  the  sun, 
Kevrpov,  a  centre).  Having  the  sun  as  a 
centre ;  a  term  applied  to  the  place  of  a 
planet,  as  seen  from  the  centre  of  the 
sun,  and  opposed  to  its  geocentric  place,  as 
seen  from  the  centre  of  the  earth. 

1.  The  heliocentric  longitude  of  a  planet 
is  the  angle  at  the  sun's  centre  formed 
by  the  projection  of  its  radius  vector  on 
the  ecliptic,  and  the  straight  line  drawn 
from  the  centre  of  the  sun  to  the  first 
point  of  Aries. 

2.  The  heliocentric  latitude  of  a  planet 
is  the  inclination  of  a  line  drawn  between 
the  centres  of  the  sun  and  the  planet,  to 
the  plane  of  the  ecliptic. 

HELIO'GRAPHY  (JjXto?,  the  sun, 
1pd<ph>,  to  write).  Photography.  A  me- 
thod of  giving  permanency  to  images  ob- 
tained by  means  of  convex  lenses,  by  the 
chemical  effects  of  light. 

HELIO'METER  (JjXtor,  the  sun,  /ne- 
rpov,  a  measure).  A  kind  of  micrometer 
invented  by  M.  Bouguer  for  measuring 
the  diameters  of  the  heavenly  bodies. 

HE'LIOSCOPE   {ii\io9,  the  sun,  <tko- 


HEM 


HEP 


Treco,  to  observe).  A  telescope  invented 
by  Scheiner,  for  making  observations  on 
the  sun  without  injuring  the  eye.  The 
usual  method  is  to  place  a  disc  of  co- 
loured glass  before  the  eye-piece  of  the 
instrument. 

HE'LIOSTAT  (JjXto?,  the  sun,  ardan, 
a  placing  or  setting).  An  instrument  by 
which  the  sun-beam  can  be  steadily  di- 
rected to  one  spot  during  the  whole  of  its 
diurnal  period. 

HE'LIOTROPE.  A  sub-species  of 
rhomboidal  quartz,  found  in  rocks  belong- 
ing to  the  secondary  trap  formation.  It 
is  termed  bloodstone,  from  the  blood-red 
specks  which  occur  on  its  green  surface, 
owing  to  disseminated  jasper. 

HELIX  (eXtf,  a  spiral).  A  spiral,  or 
winding  line;  a  coil  of  wire  used  in 
magneto-galvanic  experiments. 

HELO'PIDjE.  A  family  of  coleopte- 
rous insects,  of  the  section  heteromera 
and  sub-section  stenelytra,  named  from 
the  genus  helops,  several  species  of  which 
abound  in  England,  living  in  rotten  wood 
and  under  the  bark  of  trees. 

HE'LVINE.  A  sub-species  of  dode- 
cahedral  garnet,  found  in  beds  subordi- 
nate to  gneiss,  in  Saxony. 

HE'MATOSIN  (alfxa,  blood).  This 
and  globulin  are  two  of  the  most  charac- 
teristic constituents  of  the  blood,  both 
closely  related  to  albumen. 

HEMATO'XYLIN.  The  colouring 
matter  of  logwood,  the  wood  of  the 
Hematoxylon  campeachianum :  it  was 
named  hematin  by  Chevreul,  who  first 
distinguished  it. 

HEMERO'BIANS  (h^epa,  day,  plot, 
life).  A  family  of  neuropterous  insects, 
of  the  section  planipennes  of  Latreille, 
named  from  the  typical  genus  hemerobius, 
and,  like  the  ephemerae,  of  very  short 
existence. 

HEMI-  (nfxicvt,  half).  A  Greek  term 
frequently  employed  in  composition  to 
denote  half,  and  synonymous  with  the 
Latin  semi : — 

1.  Hem-elytra  (eXvrpov,  a  sheath).  A 
wing,  of  which  one  half  is  opaque  and 
firm,  like  an  elytrum. 

2.  Hemi-gyrus  (yupo?,  a  circle).  A  term 
applied  in  carpology,  by  Desvaux,  to  the 
fruit  of  Protaeaceae.  It  differs  little  from 
the  follicle  of  other  writers. 

3.  Hemi-hedral  (e&pa,  a  seat).  A  term 
applied  to  a  variety  in  some  forms 
of  crystals  (particularly  those  of  which 
the  cube  and  the  rhomboid  are  the  pri- 
mary), characterized  by  the  existence  of 
only  half  the  number  of  faces  belonging 

162 


to  any  particular  modification,  which  the 
law  of  symmetry  requires.  These  hemi- 
hedral  forms  are  parallel  or  oblique,  ac- 
cording to  the  relative  position  of  the 
existing  and  omitted  faces.  The  penta- 
gonal dodecahedron  is  an  example  of  the 
former  kind,  and  the  tetrahedron,  of  the 
latter.  As  the  tetrahedron  contains  half 
the  planes  by  which  the  octahedron  may 
be  derived  from  the  cube,  it  has  been 
sometimes  called  the  hemi-octahedron. 

4.  Hemi-ptera  {irrepov,  a  wing).  An 
order  of  insects,  in  which  the  anterior  or 
upper  pair  of  wings  are  coriaceous  in 
their  texture  through  one  half  of  their 
extent,  the  posterior  portion  being  thin 
and  membranous,  as  in  the  notonecta,  or 
water-boatman. 

5.  Hemisphere  (cnpaipa,  a  sphere).  A 
half -sphere,  produced  by  cutting  a  sphere 
through  the  centre  by  a  right  line  in  any 
direction;  thus  the  equator  divides  the 
sphere  of  the  earth  into  the  northern  and 
southern,  the  eastern  and  western,  the 
upper  and  lower,  hemispheres. 

6.  Hemi-tone  (toi/os,  tone).  An  inter- 
val in  ancient  music,  the  ratio  of  which  is 

m 

7.  Hemi-trope  {Tpeirw,  to  turn).  A  term 
applied  by  Haiiy  to  twin  crystals,  from 
their  being  generally  conceived  to  result 
from  cutting  a  crystal  in  halves,  and 
turning  one  portion  half  round  on  the 
other.  The  plane  common  to  the  two 
portions  of  the  crystal  is  called  the  twin 
plane,  and  is  parallel  either  to  one  of  the 
primary  planes,  or  to  a  secondary  plane 
resulting  from  some  simple  law  of  decre- 
ment. These  crystals  may  frequently  be 
recognized  by  the  existence  of  notches, 
called  re-entering  angles,  or  by  lines  on 
the  surface,  which  point  out  the  position 
of  the  twin  plane. 

HE'PAR  (hirap,  the  liver).  A  term 
formerly  applied  to  the  combinations  of 
sulphur,  from  their  liver-Uke  appearance. 
Thus  we  had  hepar  sulphuris,  a  sulphuret 
of  potash ;  hepar  antimonii,  an  oxysul- 
phuret  of  antimony ;  hepar  calcis,  a  crude 
bisulphuret  of  calcium,  &c. 

HEPA'TIC  {faap,  liver).  A  term 
applied  to  various  substances  of  a  brown 
or  liver-like  colour.  Hepatic  pyrites  is  a 
variety  of  prismatic  iron  pyrites,  which 
becomes  brown  on  exposure  to  the  air. 
Hepatic  cinnabar  is  a  dark-coloured, 
steel-grey  variety  of  cinnabar.  Hepatic 
air  is  another  name  for  sulphuretted  hy- 
drogen gas. 

HEPA'TICjE  (hrtap,  Uttcito?,  the  liver). 
The  Liver-wort  tribe  of  Acotyledonous 


HER 


HET 


plants.  Cellular,  flowerless  plants,  con- 
sisting of  an  axis  or  stem,  either  leafy  or 
bordered :  reproductive  organs  are  valved 
thecce  of  different  kinds. 

HE'PATITE  {r,irap,  liver).  A  variety 
of  heavy  spar,  or  sulphate  of  barytes, 
containing  a  minute  portion  of  sulphur, 
and  emitting,  when  heated  or  rubbed,  a 
fetid  sulphurous  odour. 

HE'PATULE  (nnap,  liver).  The  name 
given  by  Kirwan  to  the  hydrosulphuret  of 
other  writers. 

HE'PTAGON  (^tttu,  seven,  ytavia, 
angle).  In  Geometry,  a  plane  figure  of 
seven  sides.  The  area  of  a  regular  hep- 
tagon is  equal  to  the  square  of  one  of  its 
sides  multiplied  into  the  constant  num- 
ber 3.6339124,  or  seven-fourths  of  the 
tangent  of  the  angle  at  the  base  to  ra> 
dius  1. 

Heptagonal  Numbers.  A  kind  of  po- 
lygonal numbers  in  which  the  difference 
of  the  terms  of  the  corresponding  arith- 
metical progression  is  5,  thus, — 

Arithmetical*— 1,  6,  11,  16,  21,  26,  &c. 

Heptagonals—  1,  7,  18,  34,  55,  81,  &c, 
where  the  heptagonals  are  formed  by 
adding  continually  the  terms  of  the  arith- 
meticals,  above  them,  whose  common 
difference  is  5. 

HEPTAGY'NIA  (tiri-a,  seven,  yv^,  a 
woman).  The  name  of  those  orders  of 
plants  in  the  system  of  Linnaeus,  which 
are  characterized  by  the  presence  of  seven 
pistils. 

HEPTA'NDRIA  (fortt,  seven,  uvJ/p,  a 
man).  The  seventh  class  of  the  Linnaean 
system  of  plants,  characterized  by  the 
presence  of  seven  stamens. 

HERBA'RIUM  (herba,  a  herb).  A 
collection  of  dried  specimens  of  plants, 
formerly  known  by  the  expressive  term 
hortus  siccus,  or  dried  garden. 

HER'CULES.  Eugonasia.  A  northern 
constellation,  consisting  of  113  stars. 
This  constellation  has  also  been  named 
Hercules  cum  Ramo  et  Cerbero.  Its  prin- 
cipal star  is  called  Ras  Algratha. 

HE'RDERITE.  The  prismatic  fluor- 
haloid  of  Mohs ;  a  mineral  found  in 
crystals  imbedded  in  fluor,  in  Saxony, 
and  named  from  Herder,  its  discoverer. 

HERMA'PHRODITE  ('EPMrjc,  Mer- 
cury, 'A0Po3tTrj,  Venus).  A  term  ap- 
plied, in>  Botany,  to  plants  in  which  the 
stamen  and  the  pistil  are  contained  in 
the  same  flower;  all  other  flowering 
plants  being  termed  unisexual,  as  monoe- 
cious and  dioecious  plants. 

HERME'TIC  SEAL.     The  closure  of 
the  end  of  a  glass  vessel  when  heated  to 
163 


the  melting  point.  The  name  is  derived 
from  the  Egyptian  Hermes,  supposed  to 
have  been  the  father  of  chemistry,  which 
has  hence  been  called  the  Hermetic 
art. 

HERO'S  FOUNTAIN.  An  apparatus 
in  which  the  compression  of  air  is  em- 
ployed to  produce  a  jet  of  water.  Hero's 
Ball  is  a  similar  contrivance  for  the  same 
purpose.  Hero's  steam-engine  is  a  con- 
trivance for  producing  a  rotatory  motion 
by  means  of  steam,  and  was  invented 
120  years  before  the  present  era. 

HERPETO'LOGY  {tpnerov,  a  reptile, 
\6yos,  a  description).  That  branch  of 
Zoology  which  treats  of  the  structure, 
history,  and  classification  of  Reptiles. 

HER'SCHELorU'RANUS.  The  most 
remote,  but  one,  of  the  planets,  accom- 
plishing its  revolution  round  the  sun  in 
eighty-four  years.  Its  time  of  diurnal 
rotation  is  not  determined. 

HE'RSCHELITE.  A  mineral  found 
in  olivine,  brought  by  Mr.  Herschel  from 
Sicily. 

HESPE'RIDIN.  A  crystalline  sub- 
stance, obtained  from  the  skin  of  the 
unripe  orange  or  lemon, 

HESPERI'DIUM.  A  many-celled, 
superior,  in  dehiscent  fruit,  covered  by  a 
spongy  separable  rind,  as  the  orange. 

HE'TEPOSITE.  A  phosphate  of  iron 
and  manganese,  found  at  Haute  Vienne. 

HE'TERO-  (trepof,  the  other,  one  of 
two).  A  Greek  term,  in  composition 
generally  denoting  difference,  and  thus 
distinguished  from  the  term  homo-,  which 
indicates  resemblance : — 

1.  Hetero-branchiata  (fipdyxia,  gills). 
The  name  given  by  Blainville  to  the 
fourth  order  of  his  Acephalophora. 

2.  Hetero-carpien  (Kapnos,  fruit).  A 
term  applied  by  Desvaux  to  that  kind  of 
fruit  which  is  more  commonly  called 
inferior,  from  its  contracting  adhesions 
with  other  organs.  On  the  same  prin- 
ciple, he  designated  superior  fruits  as 
auto-carpien,  owing  to  their  freedom 
from  such  adhesions. 

3.  Hetero-cephalous  (Ke<f>a\rj,  the  head). 
A  term  applied  by  De  Candolle  to  those 
plants  in  which  some  of  the  capitula  are 
composed  entirely  of  male  flowers,  and 
others  entirely  of  female  flowers. 

4.  Hetero-cercal(nepKof,  a  tail  of  a  beast). 
A  term  applied  to  the  tail  of  all  the  palae- 
ozoic fishes :  their  back-bone  runs  to  a 
point  above  the  tail,  which  is  placed  be- 
below,  like  a  triangular  rudder.  This 
structure  is  still  seen  in  our  sharks, 
sturgeons,  and  in  the  sauroids  of  the 


HET 


HEX 


North  American  lakes  (bony  pike).    See 
Horn  o-cercal. 

5.  Hetero-gamous  (fdnos,  marriage). 
A  term  applied,  in  Botany,  to  those 
capitula  in  which  the  outer  flowers  are 
neuter  or  female,  and  the  inner  herma- 
phrodite or  male :  when  all  the  flowers 
are  hermaphrodite,  the  capitulum  is 
termed  homo-gamous. 

6.  Hetero-gangliata  (ydyyXiov,  a  nerve- 
knot).  A  term  applied  by  Owen  to  Cu- 
vier's  grand  division  Mollusca  of  the 
animal  world,  the  beings  of  this  division 
having  a  ganglionic  nervous  system,  and 
the  ganglions  scattered  often  unsymme- 
trically.  These  are  the  cyclogangliata 
of  Grant.     See  Homo-gangliata. 

7.  Hetero-geneous  {yevos,  kind).  A 
term  applied  to  substances  the  parts  of 
which  are  of  different  kinds,  and  there- 
fore of  different  qualities. 

8.  Helero-mera  (/uepof,  a  part).  A  sec- 
tion of  coleopterous  insects,  in  which  the 
tarsi  are  differently  parted,  the  four  an- 
terior being  five-jointed,  the  two  poste- 
rior four-jointed. — Latreille. 

9.  Hetero- trior phous  (nop<prj,  form).  Of 
an  irregular  or  unusual  form ;  a  term 
applied  to  the  larvae  of  certain  insects 
which  differ  in  form  from  the  imago,  and 
applicable  to  the  true  larval  state  of  all 
insects. 

10.  Hetero-phyllous  (<pv\\ov,  a  leaf). 
A  term  applied  to  those  plants  in  which 
the  leaves  are  not  of  the  same  kind  as 
regards  form,  &c. 

11.  Hetero-poda  (irovs,  tto56?,  a  foot). 
A  small  order  of  Gasteropods,  including 
certain  families  in  which  the  foot  is  so 
much  compressed,  as  to  constitute  a  ver- 
tical muscular  lamella,  which  presents 
merely  a  remnant  of  the  ventral  sucker, 
so  characteristic  of  the  entire  class,  and 
which  can  only  be  serviceable  in  per- 
forming the  office  of  a  fin  used  in  swim- 
ming. 

12.  Hetero-ptera  (mepov,  a  wing).  An 
order  of  insects  in  which  the  two  pairs  of 
wings  are  of  different  consistence,  the 
anterior  pair  being  horny  or  leathery, 
but  generally  tipped  with  membrane. 
They  comprise  the  land  and  the  water- 
bugs. 

13.  Heter-organa  (opyavov,  an  organ). 
By  this  term,  and  that  of  hom-organa, 
Schultz  has  divided  the  vegetable  king- 
dom into  two  primary  cla>ses,  with  re- 
ference to  the  Rotation,  or  general  motion 
of  the  sap:  the  latter  class  consisting 
wholly  or  in  great  measure  of  cellular 
tissue,   and   containing  all  the   cellular 

164 


fiowerless,  and  some  flowering,  plants  of 
a  low  organization;  the  former  all  the 
higher  flowering  plants,  and  the  vascular 
fiowerless. 

14.  Hetero-scii  (ama,  a  shadow).  This 
and  some  similar  terms,  as  amphi-scii 
and  peri-scii,  are  of  old  date,  but  still 
remain  in  works  on  the  use  of  the  globes. 
The  first  are  the  inhabitants  of  the  two 
temperate  zones,  the  noon-day  shadows 
of  each  being  always  thrown  one  way, 
but  those  of  the  two  being  always  in  dif- 
ferent ways.  The  second  are  the  inha- 
bitants of  the  torrid  zone,  who  have  their 
noon-day  shadows  sometimes  cast  north, 
sometimes  south.  The  third  are  the  in- 
habitants of  the  frigid  zones,  whose  vi- 
sible shadows  make  complete  revolu- 
tions. 

15.  Hetero-tropal  (tp€7tw,  to  turn). 
That  which  has  its  direction  across  the 
body  to  which  it  belongs,  as  applied,  in 
Botany,  to  the  embryo  of  the  seed,  as  in 
primrose. 

HEU'LANDITE.  A  mineral  formerly 
ranked  among  the  zeolites,  consisting  of 
silica,  alumina,  and  lime,  and  found  in 
the  Faroe  Isles,  the  trap  of  the  Giants' 
Causeway,  &c. 

HE'XAGON  (ef,  six,  -yow'a,  an  angle). 
In  Geometry,  a  plane  figure  bounded  by 
six  sides,  and  consequently  having  six 
angles.  The  side  of  a  regular  hexagon 
is  equal  to  the  radius  of  its  circumscri- 
bing circle.  The  area  is  equal  to  the 
square  of  the  side  multiplied  into  the  con- 
stant number  2.598076 ;  that  is,  into  three 
times  half  the  tangent  of  60°. 

HEXAGY'NIA  (ef,  six,  yvvrj,  a  wo- 
man). The  name  of  those  orders  of 
plants  in  the  Linnaean  system,  which  are 
characterized  by  the  presence  of  six 
pistils. 

HEXAHEDRON  (ef,  six,  £3pa,  a 
seat).  A  cube,  or  a  solid  geometrical 
figure,  having  six  faces.  The  whole  sur- 
face of  a  hexahedron  is  equal  to  24  times 
the  square  of  the  radius  of  the  inscribed 
sphere,  and  to  8  times  the  square  of  the 
radius  of  the  circumscribed  sphere.  Its 
solid  content  is  8  times  the  cube  of  the 
inscribed  sphere. 

HEXA'NDRIA  (ef,  six,  i^p.aman). 
The  sixth  class  of  plants  in  the  system 
of  Linnaeus,  characterized  by  the  pre- 
sence of  six  stamens. 

HE'XAPOD  (ef,  six,  nrovt,  irodbs,  a 
foot).  Six-footed ;  a  term  applied  to  ani- 
mals with  six  legs,  as  the  true  insects 
Hence,  the  term  Hexapoda  has  been  ap- 
applied  by  Mr.  Kirby  to  a  sub-order  of 


H  I  P 


HOL 


apterous  insects,  including  those  which 
have  no  more  than  six  legs. 

HIERA'TIC  WRITING  (leP6c,  sa- 
cred). A  mode  of  writing  employed  by 
the  priests  of  Egypt,  consisting  in  an 
abridged  form  of  the  hieroglyphic  cha- 
racters, adopted  for  the  sake  of  conve- 
nience and  expedition,  and  sometimes 
found  attached  to  mummies. 

HIERO'S  FOUNTAIN.  An  appara- 
tus for  raising  water,  which  acts  by  the 
elasticity  of  the  air,  and  on  the  same 
principle  as  the  fire  engine. 

HIEROGLY'PHICS  {(cpfe,  sacred, 
y\v<p<0,  to  engrave).  Sacred  engravings; 
a  term  applied  to  a  mode  of  sculpture- 
writing  employed  in  Egypt,  and  consist- 
ing of  the  images  of  visible  objects, 
chiefly  used  in  monumental  inscriptions. 
Champollion  distinguishes  three  kinds  of 
characters,  viz. — 

1.  The  hieroglyphic,  properly  so  called, 
in  which  the  figure  represents  the  object 
itself,  entire  or  in  an  abridged  form. 
These  are  termed  figurative,  and  are 
distinguished  into  figurative  proper, 
figurative  conventional,  and  figurative 
abridged. 

2.  The  symbolical,  in  which  the  figure 
of  a  visible  object  represents  an  idea ; 
thus  a  censer  represents  adoration,  the 
hawk's  eye  omniscience,  a  circle  eter- 
nity. Here,  the  symbol  indicates  an  abs- 
tract idea,  a  type  suggests  an  antitype. 

3.  The  phonetic,  in  which  the  figure 
represents  neither  an  object  nor  an  idea, 
but  a  sound.  Thus  the  letter  A  sug- 
gests the  term  "  eagle,"  being  the  initial 
letter  of  ahorn,  the  Egyptian  term  for 
that  animal.  Twenty-nine  elementary 
sounds  were  thus  represented. 

HIGH  PRESSURE  ENGINE.  A 
variety  of  the  Steam  Engine,  in  which 
the  water  is  heated  till  it  acquires  an 
expansive  force  of  from  two  to  ten  atmo- 
spheres. 

HIGHGATE  RESIN.  Fossil  Copal; 
found  in  the  bed  of  blue  clay  at  High- 
gate,  near  London.  It  is  imbedded  in 
the  clay  in  detached  nodules. 

HI'LOFERE.  A  term  applied  by 
Mirbel  to  the  internal  integument  of  the 
seed,  from  the  insertion  of  the  hilum  on 
this  part  of  the  testa. 

HI'LUM.  Umbilicus.  The  point  of 
the  seed  by  which  it  is  attached  to  the 
placenta.    This  is  the  base  of  the  seed. 

HINGE  MARGIN.  The  hinge  of 
bivalves,  composed  of  the  ligament,  the 
cartilage,  and  the  te.eth.     See  Dorsal. 

HI'PPIDES.  The  Hippa  tribe ;  the 
165 


name  by  which  Latreille  designates  a 
tribe  of  the  macrourous  decapod  crus- 
taceans, comprising  the  genera  remipes, 
albunea,  and  hippa,  animals  of  pecu- 
liar forms,  adapted  for  burrowing  in  sand. 

HIPPOBO'SCIDjE  (i'TTTror,  a  horse, 
/36aKU),  to  feed).  Forest-flies,  or  spider- 
flies  of  the  French ;  a  family  of  dipterous 
pupiparous  insects,  parasitic  on  birds 
and  quadrupeds,  of  which  the  tick  among 
sheep  is  a  well-known  example. 

HIPPOTHE'RIUM  (iWos,  a  horse, 
Otjpiov,  a  beast).  An  extinct  quadruped 
allied  to  the  horse,  found  in  sand  at 
Epplesheim,  and  belonging  to  the  second 
or  miocene  period  of  the  tertiary  forma- 
tion. 

HIPPU'RIC  ACID  (fmror,  a  horse, 
olpov,  urine).  An  acid  obtained  from 
the  urine  of  the  horse,  the  cow,  and  other 
graminivorous  animals,  when  mixed 
with  muriatic  acid  in  excess.  It  re- 
sembles benzoic  acid,  but  contains  nitro- 
gen ;  the  salts  of  the  two  acids  are,  more- 
over, distinct. 

HI'PPURITES.  A  fossil  coral  belong- 
ing to  the  Ei  el  transition  limestone,  and 
characteristic  of  the  rocks  of  the  creta- 
ceous era  in  many  parts  of  Europe.  It 
is  considered  to  be  a  bivalve,  and  is  re- 
ferred by  Lamarck  to  the  group  of  ru- 
dista. 

HI'RCIN  (hircus,  a  goat).  A  sub- 
stance, similar  to  butyrine,  contained  in 
the  fat  of  the  goat  and  the  sheep,  com- 
bined with  olein,  and  yielding,  by  saponi- 
fication, the  hircic  acid. 

HIRUNDI'NID^E  (hirundo,  a  swal- 
low). The  Swallow  tribe ;  a  family  of 
the  Insessores,  or  Perching  birds,  charac- 
terized by  the  great  length  of  their  wings 
and  the  rapidity  of  their  flight.  (See 
Fissirostres.)  By  Macgillivray,  these 
birds  are  placed  in  a  group,  belonging  to 
an  order  which  he  names  Volitatrices,  or 
gliders. 

HISI'NGERITE.  A  black  massive 
mineral,  found  in  the  cavities  of  calca- 
reous spar. 

HISTO'LOGY  (Icrrof,  a  tissue,  \670r, 
a  discourse).  The  doctrine  of  the  tissues 
which  enter  into  the  formation  of  an  ani- 
mal and  its  various  organs. 

HOAR-FROST.  This  is  an  insensible 
transition  from  dew,  being,  in  fact,  frozen 
dew,  and  indicative  of  greater  cold. 

HO'LMITE.  A  new  mineral,  consist- 
ing of  carbonate  of  lime,  named  after 
Mr.  Holme,  who  analyzed  it. 

HOLOTHU'RIDiE  {6\o0ovPiov,  a  kind 
of  zoophyte,  Arist.).    A  family  of  Echi- 


HOM 


HOR 


noderms,  commonly  termed,  from  their 
general  shape  and  appearance,  "  sea- 
cucumhers."     See  Echinodermata. 

HOMBERG'S  PHOSPHORUS.  Ig- 
nited muriate  of  lime.     See  Phosphorus. 

HOMBERG'S  PYROPHORUS  (iriJp, 
fire,  <p4p<o,  to  hring).  A  mixture  of  alum 
and  brown  sugar,  which  takes  fire  on 
exposure  to  the  air.  A  more  convenient 
mixture  is  made  with  three  parts  of  lamp- 
black, four  of  burnt  alum,  and  eight  of 
carbonate  of  potash. 

HOMBERG'S  SEDATIVE  SALT. 
A  name  for  boracic  acid,  which  appears, 
however,  to  possess  no  sedative  property. 

HO'MO-  (ojuoc ,  one  and  the  same).  A 
Greek  term,  in  composition  denoting 
resemblance,  and  thus  distinguished  from 
the  term  hetero-,  which  denotes  differ- 
ence : — 

1.  Homo-centric  (nevrpov,  a  centre). 
Having  the  same  centre,  or  being  con- 
centric. 

2.  Homo-cereal  (Kepico?,  the  tail  of  a 
beast).  A  term  applied  to  those  fishes 
which  have  tails  with  rays  regularly  di- 
verging from  the  end  of  the  backbone, 
like  the  tail  of  a  herring  or  trout.  See 
Hetero-cercal. 

3.  Homo-dromal  (5p6/xor,  a  course).  A 
term  recently  suggested,  in  Botany,  to 
characterize  the  peduncles  of  the  cyme 
of  monocotyledons,  in  which  the  direc- 
tion of  the  spire  is  the  same  as  that  of 
the  central  stem,  and  as  distinguished 
from  the  anti-dromal  direction,  which  is 
the  reverse  of  that  of  the  central  stem. 

4.  Homo-gamous  (^a/uop,  marriage).  A 
term  applied,  in  Botany,  to  those  capi- 
tula,  in  which  all  the  flowers  are  herma- 
phrodite. 

5.  Homo-gangliata  (ydfy\tov,  a  nerve- 
knot).  A  term  applied  by  Owen  to  Cu- 
vier's  grand  division  Articulata  of  the 
animal  world ;  the  beings  constituting 
this  division  having  a  ganglionic  nervous 
system,  and  the  ganglions  symmetrically 
arranged.  They  correspond  with  the  an- 
nulosa  of  Macleay,  and  the  Diploneura 
of  Grant.     See  Heiero-gangliata. 

6.  Homo-geneous  (7^1/0?,  kind).  A  term 
applied  to  substances  consisting  of  similar 
parts  and  properties,  as  distinguished 
from  hetero-geneous  substances.  Thus, 
in  minerals,  sandstone  is  a  homogene- 
ous, granite  a  heterogeneous  substance. 

7.  Homo-logous  (\6yos,  a  ratio).  Having 
the  same  ratio  or  proportion.  Equiangu- 
lar triangles,  having  sides  containing  cor- 
responding equal  angles  proportional,  are 
said  to  be  similar,  and  the  corresponding 

166 


sides  are  homo-logous,  i.  e.  having  the 
same  ratio.  Similar  magnitudes,  occu- 
pying different  places  in  a  proportion,  one 
being  an  extreme,  the  other  a  mean,  are 
said  to  be  homo-logous. 

8.  Homo-logue  (\6yos,  a  description). 
The  same  organ  in  different  animals 
under  every  variety  of  form  and  function. 

9.  Homo-morphous  {fxop<prj,  form).  Of 
similar  form ;  a  term  proposed  by  Mr. 
West  wood  for  certain  neuropterous  in- 
sects, which,  in  their  larva  state,  are 
similar  in  form  to  the  perfect  insect, 
though  wingless. 

10.  Homo-phonous  {(pasvl],  a  sound  or 
voice).  A  term  applied,  in  Music,  to  two 
or  more  sounds  which  are  exactly  of  the 
same  pitch.  In  language  the  term  is 
applied  to  words  or  syllables  which  have 
the  same  sound,  though  they  are  ex- 
pressed in  writing  by  various  combina- 
tions of  letters. 

11.  Homo-ptera  (inepov,  awing).  An 
order  of  insects  in  which  the  four  wings 
are  of  the  same  consistence,  all  of  them 
being  composed  of  a  firm  membrane,  as 
in  the  lantern-fly. 

12.  Hom-organa  (opyavov,  an  organ). 
One  of  the  primary  classes  of  plants,  as 
divided  with  reference  to  their  Rotation, 
or  general  motion  of  the  sap.  See  Heter- 
organa. 

13.  Homo-tropal  {Tpenu,  to  turn).  Hav- 
ing the  same  direction  as  the  body  to 
which  it  belongs,  but  not  being  straight, 
as  applied,  in  botany,  to  the  embryo  of  a 
seed. 

HONEY-DEW.  A  sweetish  substance 
ejected  by  very  small  homopterous  in- 
sects, called  aphides,  upon  the  leaves  of 
plants,  and  vulgarly  supposed  to  be 
caused  by  a  blight,  or  some  disease  in  the 
plant.  There  is  another  kind  of  honey- 
dew,  observed  only  at  particular  times, 
and  in  certain  states  of  the  atmosphere, 
hanging  occasionally  in  drops  from  the 
points  of  the  leaves  of  plants ;  its  cause 
is  not  known. 

HONEY-STONE.  Mellite.  Mellitate 
of  alumina ;  a  mineral  of  a  honey-yellow 
colour,  found  situated  on  bituminous 
wood  and  earth  coal,  and  usually  asso- 
ciated with  sulphur. 

HO'RARY  (hora,  an  hour).  This  term, 
as  uSed^n  astronomy,  denotes  the 
which  a  Celestial  body  describ^s^fn  one 
hour,  or  the iJmgle  whi£h«**Cnat  arc  sub- 
tends at  the  eye^^tne  spectator:  the 
horary  motion jd(  aNjelestial  body  is 
therefore  l£<br  the  twe>R£y-fourth  part 
of  a  circle; 


Horary  circles,  on  globes,  are  hour 
lines,  or  circles  marking  the  hours  ;  they 
are  drawn  at  the  distance  of  15°  on  the 
equator  from  each  other.  They  are  the 
same  as  meridians. 

HO'RDEIN  (hordeum ,  barley).  A  ve- 
getable product  found  in  barley,  supposed 
to  exist  only  in  the  husk ;  it  is  a  peculiar 
modification  of  starch. 

HORI'ZON  (opifa,  to  bound).  That 
which  bounds  any  thing,  particularly  the 
line  which  bounds  our  view  of  the  earth 
and  heavens. 

1.  The  sensible  horizon  is  a  plane  tan- 
gent to  the  globe  at  the  point  where  the 
observer  is  stationed.  It  is  the  plane  of 
the  circle  which  bounds  our  view.  When 
the  sun  rises,  he  appears  above  the 
sensible  horizon ;  and  when  he  sets,  he 
sinks  below  it. 

2.  The  rational  horizon  is  a  plane  pass- 
ing through  the  centre  of  the  earth  parallel 
to  the  sensible  horizon.  It  is  that  line 
which  would  bound  our  view,  if  we 
could  see  at  once  half  the  globe.  It  is 
represented  on  the  terrestrial  globe  by 
the  wooden  circle  which  surrounds  it. 

HORN.  A  substance  consisting  of 
coagulated  albumen  and  gelatine.  It 
differs  from  bone  in  containing  only  a 
trace  of  earth. 

HORN  SILVER.  Luna  cornea.  The 
chloride  of  silver:  the  term  is  derived 
from  its  forming  a  grey  semi-transparent 
mass,  which  may  be  cut  with  a  knife, 
and  much  resembles  horn. 

1.  Horn  Lead.  Plumbum  corneum; 
the  chloride  of  lead,  a  semi-transparent 
mass,  resembling  horn. 

2.  Horn  Quicksilver.  A  natural  proto- 
chloride  of  quicksilver,  having  a  white 
horn-like  appearance. 

HORNBLENDE.  Amphibole.  A  sili- 
cate of  lime  and  magnesia ;  a  simple 
mineral,  of  a  dark-green  or  black  colour, 
which  enters  largely  into  the  composition 
of  several  varieties  of  the  Trap  rocks. 
There  are  three  varieties,  viz.,  common 
hornblende,  hornblende-slate,  and  basaltic 
hornblende. 

1.  Hornblende-rock.  The  primitive 
greenstone  of  many  writers ;  a  crystalline 
compound  of  hornblende  and  felspar,  not 
laminar  nor  fissile,  but  massive,  although 
generally,  disposed  in  strata. 

2.  Hornblende-slate.  A  primary  rock, 
generally  of  a  distinct  slaty  structure, 
composed  of  crystals  of  hornblende,  often 
intermixed  with  felspar,  and  passing 
through  numerous  varieties  into  acti- 
nolite-slate. 

167 


3.  Hornblende  Schist.  A  term  applied 
by  M'Culloch  to  a  variety  of  mineral  ag- 
gregates in  which  hornblende  abounds, 
and  which  are  mostly,  but  not  univer- 
sally, of  laminated  structure. 

4.  Hornblendic  Clay-slate.  A  rock  of 
the  Cumbrian  group,  not  composed  of 
hornblende  and  felspar,  like  the  primary 
hornblende-slate,  but  of  clay-slate,  in 
which  are  interspersed  crystals  of  horn- 
blende and  actinolite. 

5.  Hornblendic  Granite.  A  variety  of 
granite,  in  which  hornblende  is  substi- 
tuted for  mica.  Frequently,  however, 
both  these  substances  are  associated  in 
granite,  and  the  hornblendic  gradually 
passes  into  the  common  granite.  See 
Syenite. 

HORNSTONE.  A  siliceous  mineral 
substance,  sometimes  approaching  nearly 
to  flint  or  common  quartz.  It  has  a 
conchoidal  fracture,  and  is  infusible,  by 
which  characters  it  is  distinguished  from 
common  felspar.  It  has  been  distin- 
guished into  the  splintery,  the  conchoidal, 
and  woodstone. 

HOROLO'GIUM.  The  Horologe  or 
Clock  ,  a  southern  constellation,  consist- 
ing of  twelve  stars.  It  is  cut  by  a  line 
passing  through  Canopus  to  the  southern 
part  of  Eridanus. 

HORO'LOGY  (wpa,  an  hour,  \6fos,  a 
description).  A  description  of  the  prin- 
ciples adopted  for  the  measurement  of 
time,  and  of  the  various  machines  em- 
ployed for  this  purpose.  These  comprise 
the  clepsydra  and  other  horologia  of  the 
ancients,  and  the  several  kinds  of  watches 
and  clocks  of  modern  times. 

HO'ROSCOPE  (wpa,  an  hour,  anonta, 
to  consider).  An  astrological  scheme  of 
the  twelve  signs  of  the  zodiac  at  any  par- 
ticular hour,  supposed  to  indicate  the 
future  destinies  of  any  individual  by  their 
aspect  at  the  moment  of  his  birth.  The 
signs  were  called  Houses,  as  being  the 
monthly  abodes  of  the  sun,  and,  besides, 
every  house  was  appropriated  to  some 
planet,  every  planet  having  two.  In 
a  more  particular  application  the  Ho- 
roscope  denoted  the  point  and  sign  of 
the  Ecliptic  which  rose  above  the  horizon 
at  the  hour  in  question ;  that  point 
was  the  Ascendant;  and  the  planet  to 
which  the  sign  was  appropriated  was 
termed  the  Lord  of  the  Ascendant,  and 
had  its  influence  over  the  fate  of  the  new- 
born child. 

HORSE-POWER.  A  mode  of  mea- 
suring the  performance  of  a  steam-engine 
by  reference  to  the  useful  effect  which 


HOU 


H  Y  A 


one  horse  would  produce  during  his  ordi- 
nary work.  Various  values  have  been 
affixed  to  this  unit  of  comparison ;  but  it 
is  now  generally  estimated  as  a  force 
which  would  be  capable  of  raising  a 
weight  of  33,000  lbs.  a  height  of  one  foot 
per  minute,  or  550  lbs.  per  second;  and, 
on  a  railway,  as  a  force  capable  of  trans- 
porting ,400  tons  one  mile  per  day. 

HORTUS  SICCUS.  Literally,  a  dry 
garden;  an  emphatic  appellation  given 
to  a  collection  of  specimens  of  plants, 
carefully  dried  and  preserved  :  a  more 
general  term  is  herbarium. 

HOUR.  The  twenty-fourth  part  of  a 
natural  day,  answering  to  fifteen  degrees 
of  the  equator. 

1.  Hour,  Sidereal.  The  sidereal  day 
is  four  minutes  shorter  than  the  mean 
solar  day ;  it  is  the  actual  revolution  of 
the  heavens  (see  Day).  The  astronomer 
always  makes  it  begin  when  the  vernal 
equinox  is  on  his  own  meridian ;  he  di- 
vides it  into  twenty-four  sidereal  hours 
(each  a  little  shorter  than  the  hour  of  the 
common  clock)  of  60  sidereal  minutes,  of 
60  sidereal  seconds  each,  and  he  mea- 
sures it  by  a  sidereal  clock,  with  a  pen- 
dulum a  very  little  shorter  than  that  of 
the  common  clock.  He  rejects  the  sub- 
division into  two  periods  of  12  hours 
each,  and  speaks  of  15  o'clock,  or  16 
o'clock,  under  the  phrase  15  hours  or 
16  hours,  meaning  15  or  16  hours  from 
the  commencement  of  the  sidereal  day, 
from  the  time  when  the  vernal  equinox 
was  last  on  the  meridian. 

2.  Hour  of  Angular  Measure.  The 
twenty- fourth  part  of  a  revolution  which 
is  made  in  twenty-four  hours,  and  divided 
in  reference  to  the  division  of  time.  Thus, 
an  arc  of  a  circle  is  said  to  be  a  certain 
number  of  hours,  minutes,  and  seconds, 
of  time ;  meaning,  that  the  arc  in  ques- 
tion would  be  described  in  that  number 
of  hours,  minutes,  and  seconds,  if  the 
whole  circle  were  described  in  twenty- 
four  hours.  At  this  rate,  a  revolution 
being  divided  into  360  equal  parts  or 
degrees,  15°  make  one  hour,  15'  one 
minute  of  time,  15"  one  second  of  time ; 
also,  1°  is  four  minutes  of  time,  1'  is  four 
seconds  of  time,  and  l"is  one-fifteenth 
of  a  second  of  time. 

3.  Hour-circle.  In  Astronomy,  the 
equator  is  the  principal  circle  employed ; 
it  is  the  circle  of  progression  and  regres- 
sion most  commonly  used.  All  second- 
aries to  the  equator  are  called  hour- 
circles  ;  or  rather,  each  half  of  a  secondary 
is  an  hour  smi-circle,  the  two  halves  of 

168 


the  same  secondary  belonging  to  different 
hours ;  in  fact,  a  meridian  on  the  earth 
always  answers  to  an  hour-circle  in  the 
heavens.  Every  star  is  on  one  hour- 
circle,  and  on  one  only  ;  unless  it  be  at 
one  of  the  poles  of  the  equator,  and  then 
it  is  on  all  hour-circles. 

4.  Hour-angle.  The  hour-angle  of  a 
star  is  the  angle  which  its  hour-circle 
makes  with  the  meridian  of  the  place 
(represented  by  the  brazen  hour  circle 
when  the  globe  is  properly  elevated). 
This  hour-angle  is  nothing  when  the  star 
is  on  the  meridian,  and  is  an  hour  of 
angular  measure  for  every  sidereal  hour 
to  or  from  the  time  of  the  transit,  being 
eastward  before  transit  and  westward 
after  it. 

HUM'BOLDTITE.  A  rare  mineral, 
consisting  of  a  boro-silicate  of  iron,  and 
found  in  chalcedonic  geodes  in  trap  rocks 
in  the  Tyrol.  From  this  must  be  distin- 
guished Humboldtine,  which  is  a  native 
oxalate  of  the  protoxide  of  iron. 

HU'MITE.  A  reddish-brown  mineral 
found  near  Naples  in  a  rock  of  granular 
topaz,  and  named  from  Sir  Abraham 
Hume. 

HUMMOCK.  A  sheet  of  ice,  which 
presents  a  surface  generally  level,  but 
here  and  there  diversified  by  projections, 
arising  from  the  ice  having  been  thrown 
up  by  some  pressure  or  force  to  which  it 
has  been  subject.  (See  Iceberg.)  Also,  a 
term  applied  by  navigators  to  a  circular 
and  elevated  mount  appearing  at  a  dis- 
tance. 

HUMUS.  Vegetable  mould;  woody 
fibre  in  a  state  of  decay.  The  various 
names  of  ulmin,  humic  acid,  coal  of  hu- 
mus, and  humin,  are  applied  to  modifi- 
cations of  humus. 

Humic  acid  of  chemists.  A  product 
of  the  decomposition  of  humus  by  al- 
kalies ;  it  does  not  exist  in  the  humus  of 
vegetable  physiologists. — Liebig. 

HURAU'LITE.  A  new  mineral  found 
in  the  Haute  Vienne,  consisting  of  a 
phosphate  of  iron  and  manganese. 

HURRICANE.  A  phenomenon  sup- 
posed to  be  of  electric  origin.  A  large 
vacuum  is  suddenly  created  in  the  atmo- 
sphere, into  which  vacuum  the  surround- 
ing air  rushes  with  immense  rapidity, 
sometimes  from  opposite  points  of  the 
compass,  spreading  frightful  devastation 
along  its  track. 

HY'ACINTH.  A  sub-species  of  pyra- 
midal zircon;  a  red  mineral  found  in 
volcanic  sand  in  Ceylon,  &c. 

HY'ADES  (uo),  to  rain).    The  name 


H  YD 


H  YD 


of  seven  stars  in  the  Bull's  head,  famous 
among  the  poets  for  causing  rain. 

HY'  ALINE  {va\o*,  glass).  Of  a  glassy, 
thin,  and  semi-transparent  substance. 
The  pellucid  substance  which  determines 
the  spontaneous  fission  of  cells. 

HY'ALITE  (iJaXo?,  glass).  A  siliceous 
mineral  occurring  near  Frankfort  on  the 
Maine,  in  fissures  in  vesicular  basalt  and 
basaltic  greenstone,  and  employed  by 
lapidaries  for  ring-stones. 

HYALCE'ID^l  {va\os,  glass).  A  fa- 
mily of  Pteropods  in  the  systems  of 
Cuvier  and  Lamarck,  named  from  the 
genus  hyaloca,  which  is  remarkable  for 
the  delicacy  and  transparency  of  the 
shell. 

HYBERNA'CULUM.  Literally,  a  place 
to  winter  in;  a  term  fancifully  applied 
by  Linnaeus  to  the  bud  of  a  plant,  because 
it  protects  the  young  and  tender  enclosed 
parts  during  the  winter. 

HYBERNATION  (hyberna,  winter- 
quarters).  A  reptile  ( state  of  the  func- 
tions, which  occurs  in  some  animals  in 
winter,  as  the  bat,  hedge-hog,  dormouse, 
hamster,  &c.     Compare  Diurnation. 

HY'BRID  (hybrida,  a  mongrel).  In 
Botany,  a  plant  produced  by  artificial 
fecundation ;  i.  e.  by  crossing  two  dis- 
tinct species  of  the  same  genus,  or  two 
varieties  of  the  same  species.  In  a  few 
cases,  mule  plants  have  been  artificially 
obtained  from  individuals  of  different 
genera. 

HYDATID  (Mart*,  a  vesicle).  A  term 
applied  to  several  species  of  entozoa,  or 
parasitic  animals,  which  have  a  distinct 
independent  vitality. 

HYDR-,  HYDRO-  {Mop,  water).  A 
Greek  prefix  generally  denoting  the  pre- 
sence of  water  in  definite  proportions ; 
but,  owing  to  the  changes  of  nomencla- 
ture, it  sometimes  denotes  the  presence  of 
hydrogen  in  certain  chemical  compounds. 
In  a  few  of  the  following  terms  it  relates 
to  the  hydra  or  fresh-water  polyp  : — 

1.  Hydra  {vdpa,  hydra).  A  fresh-water 
polyp,  common  in  the  ponds  and  clear 
waters  of  our  own  country,  and  affording 
an  excellent  example  of  the  structure  of 
the  Acrita,  being  destitute  of  any  percep- 
tible trace  of  nervous  substance,  of  mus- 
cular fibre,  of  a  vascular  system,  or  of 
reproductive  apparatus. 

2.  Hydra  (in  Astronomy).  The  Water- 
snake  ;  a  southern  constellation,  consist- 
ing of  sixty  stars. 

3.  Hydr-acids.  Hydro-acids;  a  class 
of  acid  compounds,  into  which  hydrogen 
enters  as  the  supposed  acidifying  prin- 


ciple, as  the  hydro-chloric,  the  hydro- 
cyanic, &c.     See  Oxacids. 

4.  Hydr-argillite  (apytWos,  clay).  Na- 
tive phosphate  of  alumina,  erroneously 
supposed  to  consist  of  alumina  and  water. 

5.  Hydrates.  Chemical  compounds  of 
bases  and  water,  still  retaining  the  solid 
form,  as  sulphur,  soap,  &c.  These  are 
also  termed  hydr-oxures  and  hydro-oxides. 
When  there  is  more  than  one  atom  of 
water,  prefixes  are  employed,  as  bin- 
aqueous,  ter-hydrate,  &c. 

6.  Hydr-aulics  {ai>\6s,  a  pipe).  That 
branch  of  Natural  Philosophy  which  in- 
vestigates the  laws  by  which  fluids  in 
motion  are  regulated,  and  consequently, 
the  construction  of  machines  in  which 
water  is  employed  as  a  moving  power,  or 
by  which  that  fluid  is  put  in  motion. 

7.  Hydraulic  Press.  An  apparatus 
contrived  or  applied  by  Mr.  Bramah,  for 
illustrating  the  hydrostatical  law  of  the 
equal  pressure  of  liquids  in  all  directions. 
A  small  quantity  of  water  is  driven  by 
sufficient  pressure  into  a  vessel  already 
full,  and  provided  with  a  moveable  sur- 
face or  piston  of  great  size.  Under  such 
circumstances  something  must  give  way ; 
the  great  surface  of  the  piston  accumu- 
lates the  pressure  on  it  to  such  an  extent 
that  nothing  can  resist  its  violence.  The 
apparatus  is  employed  in  compressing 
bodies,  in  lifting  weights,  in  raising  trees 
from  the  soil,  or  piles  from  the  beds  of 
rivers. 

8.  Hydraulic  Ram,  or  Water  Ram.  A 
hydraulic  machine  for  raising  water  by 
means  of  its  own  impulse,  invented  by 
Mr.  Whitchurch,  and  improved  by  Mont- 
golfier. 

9.  Hydr-iodic  acid.  A  gaseous  com- 
pound of  hydrogen  and  iodine,  procured 
by  the  mutual  decomposition  of  iodide  of 
phosphorus  and  water. 

10.  Hydro-benz amide.  A  colourless 
substance  obtained  by  placing  hydrate  of 
benzoile  in  a  solution  of  ammonia. 

11.  Hydro-branchia  (/3p«7X'a«  gj^s)« 
Under  thi3  term  Lamarck  includes 
the  Nudibranchia,  Scutibranchia,  and 
Tectibranchia  of  Cuvier,  together  with 
certain  genera,  which  are  arranged  in  a 
section.     Se  Pneumobranchia. 

12.  Hydro-bromic  acid.  A  gaseous 
compound  of  hydrogen  and  bromine, 
obtained  by  the  mutual  decomposition 
of  bromide  of  phosphorus  and  water. 

13.  Hydro-carbon.  A  combustible  mi- 
neral substance  found  in  the  interstices 
of  lignite.  A  compound  of  hydrogen 
and  carbon :  these  elements  combine  in 

I 


H  YD 


H  YD 


various  proportions,  forming  a  series  of 
compounds  commonly  termed  hydro- 
carburets. 

14.  Hydro-chloric  acid.  An  acid  con- 
sisting of  hydrogen  and  chlorine,  and 
long  known  under  the  names  of  spirit  of 
salt,  marine  acid,  and  muriatic  acid. 
Some  chemists  term  it  chlorhydric  acid. 

15.  Hydro-chloric  ether.  An  ether 
which  has  received  the  various  names  of 
chlorhydric,  marine,  and  muriatic  ether, 
and  hypothetically,  chloride  of  ethule. 

16.  Hydro-corisa  («6p<r,  a  bug).  The 
Water-Bugs ;  a  section  of  hemipterous 
insects,  characterized  by  their  aquatic 
habit,  and  by  a  peculiar  form  of  the  body, 
which  has  gained  for  some  of  them  the 
popular  name  of  boat-flies.  See  Geocorisa. 

17.  Hydro-cyanic  acid.  An  acid  con- 
sisting of  hydrogen  and  cyanogen,  and 
commonly  called  prussic  acid,  from  its 
having  been  procured,  though  interme- 
diately, from  Prussian  blue. 

18.  Hydro-dynamics  (3tW/itr,  power). 
The  mechanics  of  fluids ;  or  that  branch 
of  natural  philosophy  which  investigates 
the  phenomena  of  equilibrium  and  mo- 
tion among  fluid  bodies,  especially  such 
as  are  heavy  and  liquid.  It  is  distin- 
guished into  hydrostatics,  which  treats  of 
the  weight  and  pressure  of  liquids ;  and 
hydraulics,  which  treats  of  their  motion. 

19.  Hydro-electric  machine.  A  machine 
constructed  by  Armstrong  on  the  sup- 
position that  electricity  is  generated  when 
steam  is  exposed  to  friction.  On  the 
escape  of  steam  from  certain  cocks  pro- 
vided for  that  purpose,  the  pressure  being 
70  lbs.  on  the  square  inch,  an  effect 
is  obtained  7  times  greater  than  from  a 
good  electrical  machine  with  a  plate  3 
feet  in  diameter. 

20.  Hydro-fluoric  acid.  A  highly  corro- 
sive compound  of  fluorine  and  hydrogen, 
obtained  by  the  action  of  sulphuric  acid 
upon  fluor-spar,  or  fluoride  of  calcium, 
on  the  application  of  a  moderate  heat. 

21.  Hydro-gen  (>yevvd(a,  to  produce).  A 
gas  occurring  most  generally,  and  abun- 
dantly, in  combination  with  oxygen,  in 
the  form  of  water.  From  its  inflammable 
nature,  it  was  formerly  called  inflammable 
air;  and,  from  it  having  been  considered 
the  matter  of  heat,  it  was  called  phlogiston. 

22.  Hydro  graphy  (ypd^w,  to  describe). 
That  branch  of  Geography  which  treats 
of  the  water  or  seas,  which  compose  a 
part  of  the  terraqueous  globe.  Hydro- 
graphical  charts  or  maps  are  projections 
of  some  portion  of  the  ocean,  in  which  the 
rhumbs,  meridians,  parallels,  &c.  with 

170 


the  coasts,  capes,  &c.  are  laid  down  for 
the  use  of  navigation. 

23.  Hydr-oida  (et<5or,  likeness).  An 
order  of  the  polypipherous  Radiata,  con- 
sisting of  animals  allied  in  structure  to 
the  hydra.  They  are  also  called  hydri- 
form  polypes. 

24.  Hydro-logy  (\6709,  a  description). 
That  branch  of  natural  history  which 
treats  of  water,  of  irs  various  properties 
and  modes  of  existence  in  nature. 

25.  Hydro-mancy  (/j-avreia,  prophecy). 
An  ancient  superstition  respecting  the 
divining  nature  of  certain  springs  and 
fountains ;  hence,  perhaps,  arose  the  dis- 
covery of  the  medicinal  virtues  of  mineral 
waters. 

26.  Hydro-meter  {nerpov,  a  measure). 
An  instrument  for  measuring  the  gravity 
of  liquids  ;  when  floating  in  a  liquid,  it 
rises  in  proportion  as  the  density  of  the 
liquid  increases;  it  is  graduated  from 
1.000  to  1.060,  so  as  to  exhibit  at  once  the 
specific  gravity. 

27.  Hydro-metridcB.  A  family  of  he- 
mipterous insects,  named  from  the  genus 
hydrometra,  and  adapted  for  walking  on 
the  surface  of  water. 

28.  Hydr-ophidce  (6>tr,  a  snake).  Water- 
snakes;  a  family  of  Ophidian  reptiles, 
characterized  by  the  vertical  compression 
of  the  tail  and  hinder  part  of  the  body, 
by  means  of  which  they  are  enabled  to 
swim  with  facility. 

29.  Hydro-phane  ((paivw,  to  appear). 
A  variety  of  opal,  which  is  perfectly 
opaque  when  dry,  but  becomes  transpa- 
rent when  immersed  in  pure  water.  It  is 
also  called  oculus  mundi. 

30.  Hydro-jphilidce  {q>t\e(a,  to  love).  A 
family  of  coleopterous  insects,  named 
from  the  genus  hydrophilus,  and  charac- 
terized by  their  aquatic  habits. 

31.  Hydro-phyU*  {<Pvt6v,  a  plant). 
Plants  which  grow  in  water  ;  a  name 
restricted  by  botanists  to  algaceous 
plants  found  in  fresh-water. 

32.  Hydro-silicite.  A  new  mineral 
found  in  Serpentine  in  Siberia,  consist- 
ing apparently  of  pure  silica  and  water. 

33.  Hydro-statics  (water  standing). 
That  branch  of  mechanics  which  treats 
of  the  weight,  pressure,  and  equilibrium 
of  fluids,  when  in  a  state  of  rest ;  and  of 
these  properties  of  solids,  when  immersed 
in  fluids. 

34.  Hydro-static  balance.  A  balance 
for  weighing  substances  in  water,  in  order 
to  ascertain  their  specific  gravities. 

35.  Hydro-static  bellows.  An  apparatus 
for  illustrating  the  hydrostatic  paradox t 


fah 


H  YL 


HYP 


or  that  property  of  liquids  by  which  they 
transmit  pressure  equally  in  every  direc- 
tion. 

36.  Hydro-static  paradox.  A  term  de- 
noting that  any  quantity  of  fluid,  how- 
ever small,  may  be  made  to  balance  or 
counterpoise  any  quantity,  however  large. 

37.  Hydro-sulphur -et.  A  compound  of 
sulphuretted  hydrogen  with  a  salifiable 
base. 

38.  Hydro-thionic  acid  {Oelov,  sulphur). 
A  name  given  in  Germany  to  sul- 
phuretted hydrogen,  or  the  hydro-sul- 
phuric acid  of  Gay  Lussac. 

39.  Hydro-zoa  {vdpa,  hydra,  and  £Cbov, 
an  animal).  Hydriform  Polyps  ;  a  term 
applied  by  Owen  to  a  class  of  Polyps, 
which  are  organized  like  the  hydra,  or 
common  fresh-water  polype.  These  cor- 
respond with  the  Dimorphcea  of  Ehren- 
berg,  the  Serlulariens  of  Milne  Edwards, 
and  the  Nudibrachiata  of  Farre. 

40.  Hydr-uret,  or  Hydroguret.  A  com- 
pound of  hydrogen  with  a  metal. 

41.  Hydrus.  The  Water  Snake ;  a 
modern  southern  constellation,  consist- 
ing of  ten  stars. 

HYGRO'METER.  {vypo?,  moist,  yue- 
rpov,  a  measure).  An  instrument  for 
ascertaining  the  degree  of  moisture  of 
the  atmosphere.  The  quantity  of 
moisture  present  in  the  air  is  inferred 
from  the  reduction  of  temperature  re- 
quired to  produce  a  deposition  of  dew 
from  the  air ;  the  less  the  reduction  of 
temperature  required,  the  greater  the 
amount  of  moisture  in  the  air. 

Hygrometric  Water.  That  portion  of 
moisture  which  gases  yield  to  deliques- 
cent salts. 

HY'GROSCOPE  {lypbs,  moist,  <tko- 
neu),  to  examine).  An  instrument  for 
indicating  the  presence  of  aqueous  va- 
pour in  the  atmosphere,  without  mea- 
suring the  amount.  Hygroscopic  sub- 
stances are  mostly  of  animal  or  vegetable 
origin,  as  hair,  fish-bone,  animal  mem- 
branes, the  beard  of  the  wild  oat,  &c. 

HYLjE'OSAURUS  (fcAalo?,  of  the 
wood,  <ravpoi,  a  lizard).  An  extinct  gi- 
gantic land  reptile,  of  the  Wealden  strata 
of  Kent  and  Sussex,  forming,  with  the 
megalosaurus  and  iguanodon,  a  natu- 
ral and  well-marked  group  of  colossal 
animals,  connected  with  the  middle  se- 
condary period. 

HYLO'BATES  {bXapdrnv,  one  who 
haunts  the  wood).  The  name  given  by 
Illiger  to  the  long-armed  Apes  or  Gib- 
bons, which  haunt  the  forests,  and  re- 
semble the  Orangs  in  form  and  dentition. 
171 


HYME'NIUM  (vnrjv,  a  membrane). 
That  part  of  a  fungaceous  plant  in  which 
the  sporules  immediately  lie  :  in  agaricus 
it  consists  of  parallel  plates,  called  la- 
mella, or  gills. 

HYMENO'PTERA  {vfirjv,  a  mem- 
brane, Trrepov,  a  wing).  An  order  of 
mandibulate  insects,  which  have  four 
membranous,  naked,  and  unequal  wings, 
and  undergo  complete  metamorphosis,  as 
the  wasp.  They  are  distinguished  by 
Latreille  into  the  terebrantia,  in  which 
the  abdomen  of  the  females  is  furnished 
with  a  saw  or  borer ;  and  the  aculeata, 
in  which  the  abdomen  of  the  females  is 
armed  with  a  sting. 

HYPER  ({>7rep,  over  or  above).  A 
Greek  preposition,  denoting  a  position 
above,  or  excess.  In  chemical  nomen- 
clature, it  denotes  that  the  acids  to  which 
it  is  prefixed  contain  more  oxygen  than 
those  to  which  the  word  per  is  prefixed, 
as  hyper-chloric  acid.  It  corresponds 
with  the  Latin  preposition  super. 

HYPE'RBOLA  (i/7rep/9o\^,  a  throwing 
beyond).  A  section  of  a  cone  by  a  plane, 
which,  if  extended,  would  cut  the  oppo- 
site cone,  so  that  the  sections  of  both 
cones  will  exhibit  curves  expanding 
continually,  like  the  parabola,  but  with 
different  properties.  This  conic  section 
is  called  a  hyperbola,  because  the  angle 
which  its  plane  forms  with  the  base  of  the 
cone  is  greater  than  that  of  the  parabola. 
Hyperbol-oid  (etioc,  likeness).  A  geo- 
metrical solid,  formed  by  the  motion  of  a 
hyperbola  round  its  axis.  It  is  also 
termed  a  hyperbolic  conoid. 

HY'PERSTHENE.  Labrador  horn- 
blende. A  variety  of  augite,  of  a  green- 
ish-black colour,  very  similar  in  its 
general  appearances  and  characters  to 
diallage.  It  consists  of  silica,  oxide  of 
iron,  magnesia,  and  alumina. 

Hypersthene  Rock.  A  compound  of 
hypersthene  and  felspar,  the  latter  being 
compact,  crystalline,  or  glassy.  These 
form  three  varieties,  to  which  M'Cul- 
lock  has  given  the  general  name  of 
hypersthene  rock. 

HYPHA  {v<f>r),  a  web).  A  term  applied 
by  Willdenow  to  the  filamentous,  fleshy, 
watery  thallus  of  byssaceae. 

HYP-,  HYPO-  (far*,  under).  A  Greek 
preposition,  signifying  a  position  under, 
or  deficiency.  In  chemical  nomenclature 
it  denotes  the  presence  of  a  smaller 
quantity  of  acid  than  is  found  in  the 
compounds  to  which  it  is  prefixed.  It 
corresponds,  in  all  these  applications,  to 
the  Latin  preposition  sub : — 
12 


HYP 

1.  Hyp-allage  (viraWayt],  an  inter- 
change). A  figure  of  speech,  by  which 
the  parts  of  a  proposition  seem  to  be 
interchanged,  or  two  words  mutually 
exchange  their  respective  cases,  as  "  dare 
classibus  austros,"  for  dare  classes  aus- 
tris.  This  figure  has  little  place  in  cor- 
rect prose,  but  is  an  allowable  resource 
for  poets. 

2.  Hyp-anthodium.  A  term  applied  by 
Link  to  the  receptacle  of  plants  when  it 
is  fleshy,  and  not  enclosed  within  an 
involucrum,  as  in  dorstenia  and  ficus. 
See  Anthodium. 

3.  Hypo-blastus  (/3\ao-T09,  a  shoot).  A 
term  applied  by  Richard  to  the  scutelli- 
form  cotyledon  of  grasses,  which  he  con- 
siders to  be  a  particular  modification  of 
the  radicle. 

4.  Hypo-crater  if  or  m  {crater  a,  a  salver, 
forma,  likeness).  Salver-shaped  ;  as  ap- 
plied to  a  calyx  or  corolla,  of  which  the 
tube  is  long  and  slender,  and  the  limb 
flat,  as  in  phlox.  The  term  is  at  once 
unwieldy  and  unclassical :  sub-crater/form 
or  hypo-crater  old  would  be  classical,  but 
either  is  unwieldy. 

5.  Hypo-gene  Rocks  (^ivojxai,  to  be 
produced).  Those  rocks  which  are  nether- 
formed,  or  which  have  not  assumed  their 
present  form  and  structure  at  the  sur- 
face, as  granite,  gneiss,  &c.  This  term, 
which  includes  both  the  plutonic  and 
metamorphic  rocks,  is  substituted  for 
primary,  because  some  members  of  both 
these  classes,  as  granite  and  gneiss,  are 
posterior  to  many  secondary  or  fossilife- 
rous  rocks. 

6.  Hypo-geous  (yij,  the  earth).  Sub- 
terranean ;  as  applied  to  those  cotyledons 
which  remain  beneath  the  earth  after 
germination,  and  as  opposed  to  epi- 
geous. 

7.  Hypo-gynous  (ywij,  a  woman).  That 
condition  of  the  stamens  of  a  plant  in 
which  they  contract  no  adhesion  to  the 
sides  of  the  calyx,  as  in  ranunculus. 

8.  Hypo-nitrous  Acid.  The  name  given 
by  Turner  to  nitrous  acid,  or  the  azotous 
of  Thenard  ;  while  hypo-nitric  acid  is  the 
nitrous  acid  of  Turner,  or  the  peroxide 
of  nitrogen. 

9.  Hypo-phyllum  ((pvWov,  a  leaf).  A 
term  applied  by  Link  to  a  petiole  which 
has  the  form  of  a  small  sheath,  is  desti- 
tute of  blade,  and  surrounds  the  base  of 
certain  small  branches  having  the  appear- 
ance of  leaves,  as  in  asparagus. 

10.  Hypo-stasis  {biroaTCHTts,  strictly,  a 
standing  under  ;  essence,  substance).  A 
term   expressing    "  that   which    stands 

172 


H  YS 

under  (i.  e.  is  the  subject  of)  attributes." 
It  is  worth  observing,  as  a  striking  in- 
stance of  the  little  reliance  to  be  placed 
on  etymology  as  a  guide  to  the  meaning 
of  a  word,  that  "  Hypostasis,"  "  Sub- 
stantive," and  "  Understanding,"  so 
widely  different  in  their  sense,  corre- 
spond in  their  etymology. 

11.  Hypo-stasis  (in  Botany).  The  name 
given  by  Dutrochet  to  the  suspensor,  or 
delicate  thread  which  descends  from  the 
summit  of  the  ovule  into  the  quintine, 
and  bears  at  its  extremity  a  globule, 
which  is  the  nascent  embryo. 

12.  Hypo-tenuse  (vTroreivu,  to  extend 
under).  That  side  of  a  right-angled  tri- 
angle which  is  opposite  to  the  right 
angle.  Of  the  other  two  sides,  one  is 
frequently  termed  the  base,  and  the 
other  the  perpendicular. 

13.  Hypo-thecium  {$f]<n,  a  hollow  case). 
The  substance  which  surrounds  or  over- 
lies the  perithecium  of  lichens,  as  in 
cladonia. 

14.  Hypo-thesis  (viroTidr\p.i,  to  suppose). 
A  supposition,  or  doctrine,  founded  on 
theory.  The  term  is  used  synonymously 
with  system,  but,  further,  conveys  the 
uncertainty  which  attaches  to  a  system. 

15.  Hypothetical  Proposition.  In  Lo- 
gic, a  proposition  which  asserts,  not 
absolutely,  but  under  a  hypothesis,  indi- 
cated by  a  conjunction.  A  hypothetical 
proposition,  called  by  some  writers  com- 
pound, is  defined  to  be  two  or  more  cate- 
gorical! united  by  a  copula  (or  conjunc- 
tion); and  the  different  kinds  of  hypo- 
thetical propositions  are  named  from 
their  respective  conjunctions,  viz.,  con- 
ditional, disjunctive,  causal,  &c.  A  hypo- 
thetical syllogism  is  one  of  which  the 
reasoning  depends  on  such  a  proposition. 
—  Whately. 

16.  Hypo-zoic  System  {£S>ov,  an  ani- 
mal). A  geological  term,  applied  by 
Phillips  to  those  rocks  of  crystalline 
slates  which  occur  especially  in  the  cen- 
tral ridges  of  mountain  chains.  The 
term  implies  that  they  contain  no  organic 
remains,  and  that  they  are  geologically 
below  all  the  rocks  which  do  contain 
traces  of  animal  life.     See  Metamorphic. 

HYSTERA'NTHOUS  (Sarepov,  after- 
wards, avOos,  a  flower).  A  term  applied, 
in  Botany,  to  those  plants  in  which  the 
leaves  appear  after  the  flowers,  as  in 
almond. 

HYSTRFCIDjE  (Sirrpif  vel  S«r0pif, 
having  hog's  bristles;  from  5?,  a  hog, 
and  0pi£,  hair).  The  Porcupine  tribe  ;  a 
family  of  the  Rodentia,  characterized  by 


ICE 


ICH 


the  stiff  and  pointed  quills  with  which 
they  are  armed,  resembling  those  of  the 
hedge- hog,  though  usually  larger.  The 
term  porcupine  is  a  corruption  of  the 


French  porc-epin,  or  hog's-spine ;  be- 
sides, the  general  appearance  and  pecu- 
liar grunt  of  the  porcupine  are  not  unlike 
those  of  the  hog. 


IA'NTHINjE.  Oceanic  shells ;  a  sub- 
family of  the  Turbidcc,  named  from  the 
genus  ianthina,  comprising  those  fragile 
violet  and  white  snails  which  so  much 
resemble  the  Helicidce.  The  animal  is 
of  peculiar  structure. 

ICE,  POLAR.  The  poles  are  pro- 
bably surrounded  by  a  continuous  ex- 
panse of  ice,  the  borders  of  which  have 
been  explored  by  navigators,  and  desig- 
nated by  various  appellations,  in  reference 
to  the  form  and  extent  of  its  masses  :— 

1.  An  Ice-berg,  or  ice-hill,  is  a  vast 
isolated  mass  of  ice,  sometimes  rising  to 
the  height  of  100,  and  even  200,  feet 
above  the  surface,  and  extending  beneath 
it  to  a  much  greater  depth.  Ice-bergs 
are  formed  by  glaciers,  which,  some- 
times terminating  a  precipitous  edge  on 
the  coast,  and  being  gradually  protruded, 
at  length  break  off,  and  fall  into  the 
sea. 

2.  A  Field  of  Ice  is  a  continued  sheet 
of  ice,  so  large  that  its  boundaries  can- 
not be  seen  from  the  mast-head  of  a 
vessel ;  it  has  sometimes  an  area  of  more 
than  100  square  yards,  and  rises  above 
the  level  of  the  sea  from  two  to  eight 
feet.  Ice-fields  are  generated  in  the 
open  sea,  and  are  almost  constantly 
driving  in  summer,  their  general  motion 
being  south-westward.  They  acquire 
occasionally  a  rotatory  motion,  when 
their  circumference  attains  a  velocity  of 
several  miles  an  hour. 

3.  A  Pack  of  Ice  consists  of  pieces  of 
ice  broken  off  from  a  field,  when  driven 
to  the  southward,  and  exposed  to  the 
effects  of  a  ground  swell ;  these  pieces 
are  about  forty  or  fifty  yards  in  diameter, 
and  extend  so  widely  as  not  to  be  seen 
over  from  the  mast-head. 

4.  A  Patch  of  Ice  is  a  collection  of 
pieces  of  ice,  which  assume  a  circular 
form.  When  the  collection  is  of  an 
elongated  form,  it  is  called  a  stream. 
Pieces  of  very  large  dimensions,  but 
smaller  than  fields,  are  called  floes. 
Small  pieces  broken  from  larger  masses 
by  attrition,  are  called  brash-ice. 

5.  A  Hummock  of  Ice  is  a  protube- 

173 


ranee  raised  upon  any  plane  of  ice  above 
the  common  level.  A  calf  of  ice  is  a 
portion  extending  below  the  surface  of 
the  water. 

ICE-SPAR.  A  sub-species  of  prism- 
atic felspar,  of  vitreous  lustre,  translu- 
cent and  transparent,  found  at  Monte 
Somma  near  Naples. 

ICELAND-SPAR.  One  of  the  purest 
varieties  of  calcareous  spar,  or  crystal- 
lized carbonate  of  lime.  It  is  not,  how- 
ever, peculiar  to  Iceland.  Of  all  crys- 
tallized bodies,  this  exhibits  most  readily 
the  phenomenon  of  double  refraction. 

ICHNEUMO'NIDjE.  A  family  of  the 
entomophagous  Terebrantia,  named  from 
the  typical  genus  ichneumon,  and  charac- 
terized by  their  habit  of  depositing  their 
eggs  in  the  bodies  of  other  insects,  on 
which  the  young  feed,  when  hatched. 

ICHTHYODO'RULITES  (lx^f,  a 
fish,  86pv,  a  spear,  \i6os,  a  stone).  Fossil 
spear-like  projections  from  the  back  and 
belly  of  a  shark-like  fish,  supporting  fins, 
and  serving  probably  also  as  weapons. 
They  occur  in  the  carboniferous  strata, 
and  seem  to  be  identical  with  the  bony 
spine  with  which  the  Port  Jackson  shark 
is  provided. 

ICHTHYO'LOGY  (ix0ir,  a  fish,  \6yot, 
a  description).  That  branch  of  zoology 
which  treats  of  Fishes,  a  class  of  animals 
occupying  the  lowest  station  of  the  four 
great  divisions  of  the  section  Vertebrata. 
They  are  distinguished  by  Cuvier,  with 
reference  to  their  skeleton,  into  the 
Osseous  and  the  Cartilaginous. 

1.  Osseous  Fishes  are  those  which  have 
a  bony  skeleton,  the  bony  matter  being 
disposed  in  fibres;  the  sutures  of  the 
cranium  are  distinct ;  the  maxillary  and 
the  intermaxillary  bones  are,  either  one 
or  both,  present.  The  sections  are  the 
Pectinibranchii,  the  Plectognathi,  and 
the  Lophobranchii.  The  first  of  these 
comprises  the  orders  Acanthopterygii, 
Malacopterygii,  and  Apodes. 

2.  Cartilaginous  Fishes  (chondropte- 
rygii)  are  those  which  have  a  cartilagi- 
nous skeleton,  the  bones  being  destitute 
of  fibres  ;  the  sutures  of  the  cranium  are 

13 


IDE 


I  D  0 


indistinct ;  the  maxillary  and  the  inter- 
maxillary bones  are  either  wanting  or 
rudimentary,  their  place  being  supplied 
by  the  palatine  or  vomer.  The  orders  are 
the  Eleutheropomi,  Plagiostomi,  and  Cy- 
clostomi. 

ICHTHYOPHTHA'LMITE  (ix0w,  a 
fish,  o(p0a\iJios,  an  eye).  Fish-eye  stone ; 
a  species  of  zeolite,  with  a  pearly  lustre, 
resembling  the  eye  of  a  fish.  See  Apo- 
phyllite. 

ICHTHYOSAU'RUS  (ix0i/?,  a  fish, 
cavpof,  a  lizard).  A  gigantic  fossil  ma- 
rine reptile,  intermediate  in  its  characters 
between  a  crocodile  and  a  fish,  occurring 
in  the  lias  formation.  It  differs  from 
any  known  reptile  of  the  present  day,  in 
the  substitution  of  paddles  for  feet. 

I'COSAHE'DRON  (eiWt,  twenty, 
edpa,  a  seat).  In  Geometry,  a  solid  figure 
bounded  by  twenty  equal  and  equilateral 
triangles. 

ICOSA'NDRIA  (eiWt,  twenty,  avtjp, 
a  man).  The  twelfth  class  of  plants  in 
the  system  of  Linnaeus,  characterized  by 
the  presence  of  twenty  or  more  stamens 
inserted  into  the  calyx. 

IDEA  (idea,  form).  In  its  widest  accep- 
tation, this  term  denotes  an  impression 
of  an  external  object  upon  the  senses,  or 
of  an  object  of  thought  upon  the  mind. 
In  the  Platonic  philosophy  the  Ideai,  or 
"  Ideas,"  were  not  only  e'idn,  or  species, 
but  something  more,  viz.  the  perfect 
archetypes,  models  or  patterns,  of  which, 
respectively,  all  created  things  were  the 
imperfect  anti-types  or  representations; 
eldo?  might  therefore  be  used  for  idea, 
but  not  Idea  for  eidor. 

IDE'AL  THEORY.  A  scholastic 
theory,  which  refers  all  perception  to  the 
impression  on  the  mind  of  certain  ideas 
or  images  of  external  objects,  the  organs 
of  sense  having  no  percipient  power  them- 
selves, but  merely  transmitting  the  ideas 
of  these  objects  to  the  mind. 

IDE'NTICAL  {idem,  the  same).  I.  In 
its  primary  and  proper  sense,  this  term 
denotes  oneness  or  sameness,  and  is  ap- 
plicable only  to  a  single  object.  2.  In  its 
secondary  and  improper  sense,  it  is  em- 
ployed to  denote  great  similarity,  as 
when  two  guineas,  struck  from  a  wedge 
of  uniform  fineness,  are  said  to  be  "  of  one 
and  the  same  form  and  weight,  and  also  of 
one  and  the  same  substance."  Yet  they 
are  not  identical,  but  numerically  dis- 
tinct. Further,  in  this  secondary  sense, 
the  term  popularly  admits  of  degrees : 
we  speak  of  two  things  being  nearly  iden- 
tical, nearly  the  same,  but  not  entirely ; 
174 


whereas  personal  identity  does  not  admit 
of  degrees.—  Whately. 

IDEOGRA'PHIC  WRITING  (Idea, 
an  idea,  ypacpio,  to  write).  A  kind  of 
writing  by  which  objects  or  abstract  ideas 
are  symbolically  represented,  as  in  the 
figurative  part  of  the  Egyptian  hierogly- 
phics. It  is  opposed  to  phonetic  writing, 
in  which  the  symbols  employed  represent 
sounds. 

IDEO'LOGY  (idea,  an  idea,  Xdyoc,  a 
description).  By  this  term  the  later  dis- 
ciples of  Condillac  have  designated  the 
science  of  ideas,  or  the  history  and  evo- 
lution of  human  ideas,  considered  as 
successive  modes  of  certain  original  or 
transformed  sensations. 

IDIOSYNCRASY  {'idio?,  peculiar,  auy- 
upacrts,  composition).  Individual  pecu- 
liarities, hereditary  or  induced.  Thus, 
there  are  persons  in  whom  opium  does 
not  induce  sleep ;  others,  in  whom  milk 
seems  to  act  as  a  poison. 

I'DOCRASE  (etdof,  form,  Kpaan,  mix- 
ture). A  designation  of  Vesuvian  or 
Pyramidal  Garnet,  from  the  mixed  forms 
of  other  minerals  which  it  presents.  It 
is  an  alumino-silicate  of  lime,  with  a 
portion  of  oxide  of  iron. 

I'DOLS  {eUwXov,  an  image).  By  this 
fanciful  term  Lord  Bacon  points  out  the 
various  general  sources  of  those  errors 
which  we  are  apt  to  commit  in  forming 
our  notions  of  things.  These  idols,  or 
false  notions  of  the  mind,  are  divided 
into  four  classes,  viz. : — 

1.  Idols  of  the  Tribe ;  so  called  because 
they  are  common  to  the  whole  tribe  or 
race  of  mankind,  being,  in  fact,  those 
general  prejudices  which  arise  from  the 
infirmity  of  human  nature  itself.  "  The 
understanding  of  man  is  like  a  mirror 
whose  surface  is  not  true,  and  so,  mixing 
its  own  imperfection  with  the  nature  of 
things,  distorts  and  perverts  them." 

2.  Idols  of  the  Cave  or  Den ;  or  "  each 
man's  particular  demon,  or  seducing 
familiar  spirit ;"  or,  less  figuratively, 
those  prejudices  which  stamp  upon  each 
mind  its  own  peculiar  character,  and  are 
identified  with  every  individual  man. 
Every  mind  is  compared  to  "  a  glass, 
with  its  surface  differently  cut,  so  as  dif- 
ferently to  receive,  reflect,  and  refract, 
the  rays  of  light  which  fall  upon  it.w 

3.  Idols  of  the  Market-place;  or  pre- 
judices arising  from  mere  words  and 
terms  in  our  common  intercourse  with 
mankind ;  these  proceed,  in  short,  from 
the  imperfection  of  language,  and  are 
"  the  most  troublesome  of  all."    Defini- 


IGU 


1MB 


tions  themselves  cannot  wholly  remedy 
the  evil;  for  "definitions  consist  of 
words,  and  words  produce  words;  so 
that  recourse  must  he  had  to  particular 
instances." 

4.  Idols  of  the  Theatre ;  or  the  preju- 
dices and  perversions  of  the  mind  arising 
from  fabulous  and  visionary  theories  and 
romantic  philosophies.  They  are  thus 
named,  "because  all  the  systems  of  phi- 
'  losophy  which  have  been  hitherto  in- 
vented, or  received,  are  but  so  many 
stage-plays  which  have  exhibited  nothing 
but  fictitious  and  theatrical  worlds  ;  and 
there  may  still  be  invented  and  dressed 
up  numberless  other  fables  of  the  same 
kind." 

I'DRIALINE.  A  substance  obtained 
from  a  mineral  from  the  quicksilver 
mines  at  Idria  in  Carniola.  It  consists  of 
carbon  and  hydrogen. 

IGASURIC  ACID.  The  name  given 
by  Pelletier  and  Caventou  to  a  peculiar 
acid,  which  occurs  in  combination  with 
strychnia  in  nux  vomica,  and  the  St.  Ig- 
natius's  bean ;  but  its  existence,  as  dif- 
ferent from  all  other  known  acids,  is 
doubtful.  It  is  so  called  from  the  Malay 
name  by  which  the  natives  in  India  de- 
signate the  faba  Sancti  Ignatii. 

I'GNEOUS  ROCKS  {ignis,  fire).  A 
term  applied  to  all  rocks,  as  lava,  trap, 
and  granite,  which  are  known  or  sup- 
posed to  have  been  melted  by  volcanic 
heat. 

IGNIS  FATUUS.  A  luminous  ap- 
pearance or  flame,  frequently  seen  in 
the  night  in  the  country,  and  called  Jack 
o'  lantern,  or  Will  with  the  wisp.  It  is 
probably  occasioned  by  the  extrication 
of  phosphorus  from  rotting  leaves  and 
other  vegetable  matters. 

IGNITION  {ignis,  fire).  The  emission 
of  light  from  a  heated  body,  unattended 
by  change  of  composition.  Bodies  begin 
to  become  ignited,  or  red-hot,  at  about 
800°  Fahr. ;  the  highest  point  of  ignition 
consists  in  the  emission  of  a  perfectly 
white  light. 

I'GREUSINE.  Elaiodon.  That  por- 
tion of  volatile  oils  which  is  odoriferous, 
and  is  coloured  by  treating  it  with  nitric 
acid. 

IGUA'NIDJE.  A  family  of  saurian 
reptiles,  including  some  of  the  largest  of 
this  tribe,  both  recent  and  fossil.  They 
agree  with  the  lizards  in  general  form, 
but  differ  in  the  shortness  and  thickness 
of  their  tongues.    See  Iguanodon. 

IGUA'NODON  {iguana,  a  recent  West 
Indian  lizard,  b6oi>s,  a  tooth).    A  gigantic 
175 


fossil  saurian,  exceeding  eighty  feet  in 
length,  occurring  in  the  Wealden  forma- 
tion, and  known  to  us  by  the  teeth  and  a 
considerable  part  of  the  skeleton.  Its 
name  is  derived  from  the  resemblance  of 
its  teeth  to  those  of  the  iguana. 

I'LLATIVE  CONVERSION.  In  Logic, 
a  mode  of  conversion  in  which  the  truth 
of  the  converse  follows  from  the  truth  of 
the  exposita,  or  proposition  given.  Con- 
version can  then  only  be  illative,  when 
no  term  is  distributed  in  the  converse, 
which  was  not  distributed  in  the  expo- 
sita. Illative  conversion  is  not  a  process 
of  reasoning ;  it  is  only  stating  the  same 
judgment  in  another  form.  See  Con- 
version. 

ILLUMINATION  {illumino,  to  throw 
light  upon).  The  process  of  rendering  a 
body  visible  by  light:  every  object  ex- 
posed to  the  sun  is  illuminated  ;  a  lamp 
illuminates  a  room  and  every  object 
in  it. 

IMAGE.  The  appearance  of  an  ob- 
ject made  either  by  reflection  or  refrac- 
tion. In  all  plane  mirrors,  the  image  is 
of  the  same  magnitude  as  the  object,  and 
it  appears  as  far  behind  the  mirror  as  the 
object  is  before  it.  In  concave  mirrors 
the  image  appears  larger,  and  in  those 
which  are  convex  it  appears  less,  than 
the  object. 

Image,  Aerial.  When  an  object  is 
placed  at  a  greater  than  its  focal  distance 
from  a  convex  lens,  it  produces  on  the 
opposite  side  of  the  glass  an  inverted 
image  floating  in  the  air;  hence  called 
an  aerial  image. 

IMA'GINARY  QUANTITIES.  In 
Algebra,  this  term  is  applied  to  the  even 
roots  of  negative  quantities,  as  sj — x3. 
Such  expressions  indicate  operations 
which  are  impossible,  and  hence  they  are 
also  called  impossible  quantities.  The 
difference  between  surd  and  impossible 
quantities  is,  that  the  former  have  real 
values,  though  we  cannot  exactly  find 
them,  while  there  cannot  be  a  quantity, 
positive  or  negative,  an  even  power  of 
which  would  produce  a  negative  quan- 
tity. 

IMA'GO.  A  term  applied  to  the  third 
and  perfect  state  of  insect  existence,  in 
which,  the  skin  of  the  pupa  having 
burst,  the  animal  escapes,  furnished 
with  wings  adapted  for  flight. 

IMBIBI'TION  {imbibo,  to  drink  in). 
The  terms  imbibition,  and  exudation  or 
transpiration,  used  in  Physiology,  are 
analogous  to  those  of  aspiration  and  ex- 
piration, and  have  been  lately  translated, 
14 


I  MP 


INC 


by  Dutrochet,  by  the  two  Greek  words 
endosmosis  and  exosmosis. 

I'MBRICATED  {imbrex,  a  roof-tile). 
A  designation  of  that  form  of  aestivation, 
or  vernation,  in  which  the  pieces  of  the 
bud  overlap  each  other  parallelly  at  the 
margins,  without  any  involution.  The 
term  is  particularly  applicable  to  the 
bracts  of  glumaceous  plants. 

IMMER'SION  (immergo,  to  plunge 
into).  An  astronomical  term,  denoting 
the  disappearance  of  any  celestial  body 
behind  another  or  in  its  shadow,  as  in 
the  eclipses  of  Jupiter's  satellites.  The 
re-appearance  of  the  body,  after  occupa- 
tion, is  termed  its  emersion. 

I'MPACT  {impingo,  to  impinge).  By 
Impact  or  Percussion  is  meant  the  colli- 
sion of  two  bodies,  of  which  one  at  least 
is  in  motion.  The  impact  is  said  to  be 
central,  when  the  directions  of  the 
centres  of  gravity  of  the  two  solid  bodies 
are  in  a  right  line ;  eccentric,  when  this 
is  not  the  case ;  direct  or  perpendicular, 
when  the  direction  of  the  moving  body  is 
at  right  angles  to  the  side  of  the  body 
impinged  on ;  oblique,  when  this  is  not 
the  case. 

I'MPARI-PINNATE.  A  term  ap- 
plied, in  Botany,  to  that  mode  of  the 
composition  of  leaves,  in  which  they  are 
pinnate  with  an  odd  one,  as  when  the 
petiole  of  a  pinnate  leaf  is  terminated  by 
a  single  leaflet,  as  in  mountain-ash. 

IMPE'NETRABI'LITY  {in,  not,  pene- 
tro,  to  penetrate).  That  property  by 
which  a  body  occupies  any  space,  to  the 
exclusion  of  every  other  body.  In  a 
popular  sense,  all  matter  is  penetrable; 
but,  philosophically  speaking,  it  is  im- 
penetrable, what  is  called  penetration 
being  merely  the  admission  of  one  sub- 
stance into  the  pores  of  another.  A  nail 
driven  into  a  board  or  piece  of  lead,  does 
not  penetrate  the  wood  or  metal;  it 
merely  separates  or  displaces  the  particles 
of  these  substances. 

IMPERATIVE  MOOD  {impero,  to 
command).  That  mood  of  the  verb 
which  commands  an  action  to  be  per- 
formed, or  a  state  to  exist. 

IMPO'NDERABLES  {in,  priv.,  pon- 
dus,  weight).  Agents  which  are  desti- 
tute of  weight,  as  heat,  light,  and  elec- 
tricity. These  are  supposed  to  be  of  so 
subtile  a  nature  as  to  pass  through  all 
material  bodies,  by  which,  therefore,  they 
cannot  be  either  enclosed  or  divided. 

IMPOSSIBILITY.  This  term  is  used 
in  three  different  senses : — 

1.  A  mathematical  impossibility  is  that 
176 


which  involves  an  absurdity  and  self- 
contradiction,  as  that  two  straight  lines 
should  enclose  a  space.  No  limitation 
of  power  is  here  implied ;  it  is,  in  reality, 
nothing  that  is  required  to  be  done. 

2.  A  physical  impossibility  is  some- 
thing at  variance  with  the  existing  laws 
of  nature,  and  which,  consequently,  no 
being,  subject  to  those  laws,  can  sur- 
mount ;  but  we  can  easily  conceive  a 
Being  capable  of  bringing  about  what  in  * 
the  ordinary  course  of  nature  is  impos- 
sible. An  occurrence  of  this  character 
we  call  miraculous. 

3.  A  moral  impossibility  is  that  high 
degree  of  improbability  which  leaves  no 
room  for  doubt.  This  implies  no  contra- 
diction, nor  any  violation  of  the  laws  of 
nature,  but  which  yet  we  are  rationally 
convinced  will  never  occur,  merely  from 
the  multitude  of  chances  against  it ;  as 
that  unloaded  dice  should  turn  up  the 
same  faces  one  hundred  times  succes- 
sively. And  yet  why  should  they  not  ? 
since  the  chances  are  the  very  same 
against  any  given  one  hundred  throws. — 
Whately. 

IMPOSSIBLE.  In  Logic,  the  matter 
of  a  proposition  is  said  to  be  impossible, 
when  the  extremes  altogether  disagree. 
The  proposition  is  then  equivalent  to  a 
universal.  Thus,  brutes  neither  eat  nor 
drink  more  than  nature  requires ;  that  is, 
no  brutes,  #c. 

An  impossible  quantity,  in  Algebra,  is 
the  same  as  an  imaginary  quantity.  See 
the  latter  term. 

I'MPULSE  {impulsus,  a.  push  or  stroke). 
The  direct  action  of  one  body  upon  an- 
other in  the  production  of  motion.  Bodies 
are  impelled,  or  driven  forward,  either 
by  percussion  or  by  pressure — by  a  stroke, 
as  by  a  hammer,  or  by  a  push,  as  by  a 
spring  or  living  power.  The  former  is 
instantaneous,  the  latter  continuous.  In 
both  cases  the  moving  body  flies  from 
the  power;  in  the  action  of  pulling,  or 
attraction,  it  does  the  reverse. 

INCANDE'SCENCE  {incandesco,  to 
become  white-hot).  The  glowing  or 
shining  appearance  of  heated  bodies; 
properly,  the  acquisition  of  a  white 
heat. 

INCEPTIVE  (incipio,  to  begin).  That 
which  begins  any  thing ;  a  term  some- 
times applied  to  a  moment  or  principle, 
from  which,  as  from  a  starting-point, 
something  may  be  extended;  thus  a 
point  or  a  line,  in  mathematics,  though 
possessing  no  magnitude,  is  said  to  be 
inceptive  of  enlargement.    But  this  is  a 


INC 


IND 


verbal  fallacy ;  for  that  which  has  no 
parts,  cannot  be  enlarged. 

I'NCIDENCE  (incido,  to  fall  upon). 
The  direction  in  which  one  body  strikes 
on  another.  The  term  is  used  in  different 
senses  by  writers  on  mechanics  and 
writers  on  optics.  See  Angle  of  Incidence, 
in  each  case. 

INCINERATION  {incinero,  to  re- 
duce to  ashes,  from  cinis,  a  cinder).  The 
reducing  to  ashes  by  burning.  The  com- 
bustion of  vegetable  or  animal  substances 
for  the  purpose  of  obtaining  their  ashes 
or  fixed  residue. 

TNCI'SION  (incido,  to  cut).  This  term 
must  be  distinguished  from  the  ccesura 
of  metre.  Incision  is  the  coincidence  of 
the  end  of  the  foot  with  the  end  of  the 
word ;  it  is  essential  in  some  species  of 
verse,  and  is  used  also  in  the  hexameter 
under  certain  forms. 

INCLINATION.  In  mathematics, 
the  mutual  approach  of  two  lines,  or 
planes,  towards  each  other,  so  as  to  make 
an  angle.  The  inclination  of  the  orbit 
of  a  planet  is  the  angle  which  the  plane 
of  the  planet's  orbit  makes  with  the 
ecliptic,  or  the  earth's  orbit.  The  in- 
clination, or  dip  of  the  magnetic 
needle  is  the  angle  which  such  needle, 
when  supported  on  its  centre  of  gra- 
vity, makes  with  the  plane  of  the  ho- 
rizon. 

INCLINED  PLANE.  One  of  the 
five  simple  mechanical  powers,  con- 
sisting of  a  plain  smooth  surface,  which 
is  inclined  towards  or  from  the  earth.  A 
board,  with  one  end  on  the  ground,  and 
the  other  end  resting  on  a  block,  becomes 
an  inclined  plane. 

INCLU'SA  (includo,  to  enclose).  An 
order  of  the  conchiferous  acephalous 
mollusca,  in  which  the  mantle  has  only 
one  opening  for  the  passage  of  the  foot ; 
at  the  posterior  end  it  is  prolonged  into 
tubes  of  great  length,  which  can  be  ex- 
tended far  beyond  the  shell,  as  in  the 
common  solens  or  razor-shells. 

INCOMBUSTIBLE  CLOTH.  A  cloth 
manufactured  of  the  fibres  of  asbestos  ; 
on  burning  away  the  fibre,  the  mineral 
texture  remains. 

INCOMME'NSURABLES.  Any  two 
magnitudes  which  cannot  be  represented 
by  means'  of  the  same  unit,  and  cannot 
consequently  have  any  common  measure, 
are  said  to  be  incommensurable,  as  the 
diagonal  and  the  side  of  a  square.  Num- 
bers are  said  to  be  incommensurable 
in  power,  when  their  squares  or  second 
powers  are  incommensurable,  as  2  and  3, 
177 


the  squares  of  which.  4  and  9,  have  no 
common  measure. 

INCOMPAT1BLES,  CHEMICAL.  A 
term  applied  to  salts  or  other  compounds, 
which  cannot  exist  together  in  solution, 
without  mutual  decomposition,  as  the 
salts  of  barytes  and  those  which  contain 
sulphuric  acid. 

INCOMPRESSIBILITY.  That  pro- 
perty of  a  substance,  whether  solid  or 
fluid,  by  which  it  resists  being  pressed 
or  squeezed  into  a  smaller  bulk.  The 
ultimate  particles  of  all  bodies  are  sup- 
posed to  be  incompressible. 

INCREMENTS,  METHOD  OF.  A 
method  of  analysis,  more  commonly 
called  the  calculus  of  finite  differences. 
In  the  higher  mathematics,  the  terms 
increment  and  decrement  are  employed, 
when  two  quantities  are  considered  toge- 
ther, one  of  which  is  greater  or  less  than 
the  other ;  the  latter  is  then  said  to  be 
the  former  with  an  increment  or  decre- 
ment. 

INCU'MBENT  (incumbo,  to  lie  upon). 
That  which  lies  upon  any  thing ;  a  term 
applied,  in  Botany,  to  the  cotyledons  of 
those  cruciferous  plants,  which  are  folded 
with  their  backs  upon  the  radicle.  See 
Accumbeni. 

INDEFINITE.  In  Geometry,  this 
term  is  applied  to  a  straight  line,  which 
may  be  produced  to  any  length  in  a  given 
direction,  without  affecting  the  conditions 
of  the  problem.  The  term  is  sometimes 
used  in  the  sense  of  infinite,  as  when  we 
hear  of  a  magnitude  being  indefinitely 
great,  an  indefinitely  small  arc  being 
equal  to  its  chord,  a  circle  being  a  poly- 
gon of  an  indefinitely  great  number  of 
sides,  &c. 

INDEFINITE  PROPOSITION.  In 
Logic,  a  proposition  which  has  for  its 
subject  a  common  term  without  any  sign 
to  indicate  distribution  or  non-distribu- 
tion. In  these  cases,  the  quantity  of  a 
proposition  is  ascertained  by  the  matter, 
or  the  nature  of  the  connexion  between 
the  extremes :  in  necessary  and  in  impos- 
sible matter,  an  indefinite  is  understood 
as  a  universal ;  in  contingent  matter,  as 
a  particular. 

INDEFINITE  TERM.  In  Logic,  a 
privative  or  negative  term  is  called  inde- 
finite, in  respect  of  its  not  defining  or 
marking  out  an  object ;  and  it  is  opposed 
to  a  definite  or  positive  term,  which  does 
define  or  mark  out.  Thus,  "  organized 
being"  is  a  definite,  "unorganized  being" 
an  indefinite  term. 

INDEHFSCENT  (in,  not,  dehisco,  to 
15 


IND 


IND 


gape).  A  term  applied,  in  Botany,  to 
the  state  of  those  fruits  in  which  the 
pericarp,  when  arrived  at  maturity,  con- 
tinues perfectly  closed,  as  in  the  hazel 
nut.    See  Dehiscence. 

INDE'NTED.  A  term  applied  to  any 
part  of  a  body  which  is  depressed  or  sunk 
beneath  the  surrounding  surface,  whether 
the  indentations  consist  of  lines,  dots, 
irregular  cavities,  or  tooth-like  depres- 
sions. 

INDEPENDENT  COAL  FORMA- 
TION. By  this  term  Werner  designated 
the  first  or  oldest  formation,  because  the 
individual  depositions  of  which  it  is  com- 
posed are  independent  of,  and  uncon- 
nected with,  one  another.  It  contains 
exclusively  coarse  coal,  foliated  coal, 
cp.nnel  coal,  slate  coal,  a  kind  of  pitch 
coal,  and  slaty  glance  coal. 

INDESTRUCTIBI'LITY.  That  pro- 
perty of  matter  by  virtue  of  which  it 
never  ceases  to  exist :  it  may  change  its 
form,  and  disappear ;  but  it  is  not  anni- 
hilated. In  what  is  called  destructive 
distillation,  the  matters  subjected  to  the 
operation  are  evidently  indestructible ; 
for  the  products,  when  collected  and 
weighed,  are  found  to  be  exactly  as 
heavy  as  the  original  matters. 

INDETE'RMINATE.  1.  In  Mathe- 
matics, a  problem  is  said  to  be  inde- 
terminate, when  it  admits  of  an  infi- 
nite number  of  solutions.  2.  In  Algebra, 
the  co-etficients  of  an  assumed  form  of 
expansion  are  said  to  be  indeterminate, 
and  the  process  by  which  they  are  then 
found,  is  called  the  "method  of  indeter- 
minate co-efficients."  3.  If  owe  equation 
contain  two  unknown  quantities,  the 
number  of  values  of  these  by  which  it 
will  be  satisfied,  is  unlimited,  and  the 
equation  is  said  to  be  indeterminate. 

INDEX  {indico,  to  point  out).  1.  In 
Algebra,  a  small  figure  placed  at  the  right 
of  a  quantity,  to  signify  its  power  (See 
Exponent).  2.  The  index  of  a  logarithm, 
or  its  characteristic,  is  the  5gure  prefixed 
to  the  logarithm  for  the  purpose  of  indi- 
cating the  unit's  place  in  the  correspond- 
ing number.  3.  In  optics,  the  index  of 
refraction  is  the  constant  ratio  which  ex- 
ists between  the  sines  of  the  angles  of 
incidence  and  refraction. 

FNDIANITE.  A  whitish  or  greyish 
mineral,  consisting  of  silica,  alumina, 
lime,  iron,  and  manganese,  occurring  in 
masses  in  the  Carnatic,  where  it  consti- 
tutes the  gangue  of  corundum. 

INDICATIVE  MOOD  {indico,  to 
point  out).  In  Grammar,  that  condition 
178 


of  the  verb  which  declares  the  action  or 
state  to  exist  simply  and  as  a  fact. 

INDFCTION.  In  Chronology,  a  re- 
volution of  fifteen  years,  as  already  no- 
ticed under  the  term  Era.  Its  origin 
has  not  been  ascertained ;  but  Gibbon 
observes,  that  the  name  and  use  of  the 
"Indictions"  were  derived  from  the 
Roman  tributes.  There  are  four  descrip- 
tions of  Indictions  :— 

1.  The  Indiction  of  Constantinople, 
which  was  instituted  by  Constantine  in 
a.  d.  312,  and  began  on  the  1st  of  Sep- 
tember. 

2.  The  Imperial  or  Cesarean  Indiction, 
which  began  on  the  24th  of  September. 

3.  The  Roman  or  Pontifical  Indiction, 
which  commences  on  the  25th  of  Decem- 
ber or  1st  of  January,  according  as  either 
of  these  days  was  considered  as  the  first 
of  the  year.  This  was  generally  used  in 
papal  bulls,  at  least  from  the  ninth  to 
the  fourteenth  century. 

4.  The  fourth  kind  of  Indiction,  which 
is  to  be  found  in  the  register  of  the  par- 
liaments of  Paris,  began  in  the  month  of 
October. 

INDI'FFERENCE.  This  term,  in  its 
application  in  respect  of  the  will  and  of 
the  judgment,  is  subject  to  an  ambiguity 
which  may  perhaps  be  thought  hardly 
worth  noticing,  the  distinction  between 
unbiassed  candour  and  impartiality  on 
the  one  side,  and  carelessness  on  the 
other,  being  so  very  obvious.  Yet,  under 
the  same  name,  these  things  are  con- 
founded ;  and,  in  fact,  the  judgment  is 
often,  though  by  no  means  always,  biassed 
by  the  will.  Our  aim  should  be  to  pre- 
serve the  indifference  of  the  judgment, 
even  where  the  will  neither  can  nor  should 
be  indifferent.  —  Whately. 

INDFGENOUS  (indigena,  a  native). 
A  term  applied  to  animals  or  plants  pe- 
culiar to  a  certain  country. 

INDIGO.  A  blue  pigment,  obtained 
from  the  leaves  of  all  the  species  of 
Indigofera,  and  various  other  plants. 
White  indigo,  also  called  reduced  indigo, 
is  procured  by  the  action  of  deoxidizing 
bodies  upon  blue  indigo;  in  this  state, 
Liebig  termed  it  indigogen. 

FNDIGOLITE.  An  indigo-coloured 
crystallized  mineral,  found  at  Utoe  in 
Sweden,  and  considered  to  be  a  variety 
of  tourmaline. 

INDIGO'TIC  ACID.  Anilic  Acid.  An 
acid  formed  when  indigo  is  dissolved  in 
nitric  acid  considerably  diluted.  This  is 
the  nitranilic  acid  of  Berzelius. 

INDIVI'DUAL  {individuus,  that  can- 


IND 


INF 


not  be  divided).  An  object  which  is,  in 
the  strict  and  primary  sense,  One,  and, 
consequently,  cannot  be  logically  divided  ; 
which  is  a  metaphorical  expression  to 
signify  "'the  distinct  (i .  e.  separate)  enu- 
meration of  several  things  signified  by 
one  common  name."  This  operation  is 
directly  opposite  to  generalization,  which 
is  performed  by  means  of  abstraction; 
for  as,  in  that,  we  lay  aside  the  differences 
by  which  several  things  are  distinguished, 
so  as  to  call  them  all  by  one  common 
name,  so,  in  Division,  we  add  on  the  dif- 
ferences, so  as  to  enumerate  them  by  their 
several  particular  names.  Thus  "mine- 
ral" is  said  to  be  divided  into  "  stones," 
"  metals,"  &c. ;  and  metals  again  into 
"  gold,"  "  iron,"  &c. ;  and  these  are  called 
the  parts,  or  members  of  the  division. — 
Whately. 

INDIVISIBLES,  METHOD  OF.  A 
method  formerly  employed  in  Algebra, 
founded  on  the  assumption  that  quan- 
tities are  composed  of  infinitely  small 
quantities  incapable  of  further  division. 
It  was  a  kind  of  atomic  theory,  by  which 
lines  were  considered  as  made  up  of  an 
infinite  number  of  points,  surfaces  of  an 
infinite  number  of  lines,  and  solids  of  an 
infinite  number  of  surfaces.  The  method 
has  been  entirely  superseded  by  the  dif- 
ferential and  integral  calculus. 

INDU'CTION  {induco,  to  bring  in,  to 
infer).  A  kind  of  argument  which  in- 
fers, respecting  a  whole  class,  what  has 
been  ascertained  respecting  one  or  more 
individuals  of  that  class.  Induction,  so 
far  as  it  is  an  argument,  may,  of  course, 
be  stated  syllogistically ;  but  so  far  as  it 
is  a  process  of  inquiry  with  a  view  to  ob- 
tain the  premises  of  that  argument,  it  is, 
of  course,  out  of  the  province  of  logic ; 
and  the  latter  is  the  original  and  strict 
sense  of  the  word. — Whately. 

INDU'CTION  (in  Electricity).  The 
law  by  which  an  electrified  body  induces, 
or  tends  to  produce,  in  contiguous  sub- 
stances an  electric  state  opposite  to  its 
own. 

INDU'CTIVE  SCIENCE.  A  science 
which  ascends  from  particular  facts  to 
general  principles,  and  descends  from 
these  general  principles  to  particular  ap- 
plications. Induction  is  the  opposite  of 
hypothesis,  which  consists  in  laying  down 
a  theory  at  the  outset  of  an  inquiry,  and 
trusting  to  future  experiments,  or  ex- 
ample, for  its  proof. 

INDUCTOMETER,       DIFFEREN- 
TIAL.   An  instrument,   so    named   by 
Faraday,   consisting  of  three   insulated 
179 


metallic  plates,  placed  parallel  to,  and  at 
equal  distances  from,  one  another,  each 
exterior  plate  being  connected  with  an 
insulated  gold-leaf  of  an  electrometer. 

INDUS.  The  Indian ;  a  modern  south- 
ern constellation,  consisting  of  twelve 
stars,  situated  between  Sagittarius  and 
the  South  Pole. 

INDU'SIAL  LIMESTONE.  A  fresh- 
water limestone,  abounding  in  the  indu- 
siae  of  the  larva  of  phrygania,  encrusted 
by  hard  travertin  and  converted  into 
rock. 

INDU'SIUM  (induo,  to  put  on).  A 
term  applied,  in  Botany,  to  that  portion 
of  the  epidermis  of  ferns  which  covers 
the  sori;  also,  to  the  peculiar  form  as- 
sumed by  the  hairs  of  the  style  in  certain 
plants,  when  they  are  united  into  a  cup, 
enclosing  the  stigma,  as  in  Goodeniaceae. 

INDU'VI^  (induvice,  clothes).  In 
Botany,  this  term  denotes  the  withered 
remains  of  leaves,  which,  not  being  arti- 
culated with  the  stem,  do  not  fall  off,  but 
decay  with  it.  A  part  so  covered  is  said 
to  be  induviate. 

INE'NCHYMA.  A  term  applied  by 
Morren  to  the  fibro-cellular  tissue  of 
plants. 

INEQUALITY.  1.  In  Algebra,  if 
one  quantity  be  greater  or  less  than 
another,  or  than  nothing,  and  this  be 
expressed  algebraically,  it  is  called  an 
inequality.  Thus  *  —  a>b—x  is  an 
inequality,  of  which  x — a  forms  one 
side,  and  b — x  the  other.  2.  In  Astro- 
nomy, the  term  denotes  any  deviation  in 
the  motion  of  a  planet  or  satellite  from 
its  uniform  mean  motion. 

INE'RTIA  (iners,  inactive).  That 
property  of  matter  by  which  it  would  al- 
ways continue  in  the  same  state  of  rest 
or  motion  in  which  it  was  put,  unless 
changed  by  some  external  force.  The 
quantity  of  matter  of  a  body  is  deter- 
mined by  its  quantity  of  inertia ;  and 
this  is  estimated  by  the  quantity  of  force 
required  to  put  it  in  motion  at  a  given 
rate. 

IN  ESSE;  IN  POSSE.  The  former 
of  these  Latin  terms  is  applied  to  things 
which  do  actually  exist;  the  latter,  to 
things  which  do  not,  but  may,  actually 
exist. 

INFERENCE  AND  PROOF.  "  Rea- 
soning comprehends  Inferring  and  Prov- 
ing ;  which  are  not  two  different  things, 
but  the  same  thing  regarded  in  two  dif- 
ferent points  of  view :  like  the  road  from 
London  to  York,  and  the  road  from  York 
to  London.  He  who  infers,  proves ;  and 
16 


INF 


INN 


he  who  proves,  infers;  hut  the  word 
•  infer '  fixes  the  mind  first  on  the  pre- 
miss and  then  on  the  conclusion;  the 
word  '  prove,'  on  the  contrary,  leads  the 
mind  from  the  conclusion  to  the  premiss. 
Hence,  the  substantives  derived  from 
these  words  respectively,  are  often  used  to 
express  that  which,  on  each  occasion,  is 
last  in  the  mind ;  Inference  being  often 
used  to  signify  the  conclusion  (i.  e.,  pro- 
position inferred),  and  Proof,  the  pre- 
miss. To  infer,  is  the  business  of  the 
philosopher ;  to  prove,  of  the  advocate" — 
Whately. 

INFERIOR  FRUIT.  In  Botanical 
language,  a  fruit  or  ovary  is  termed  infe- 
rior, when  the  calyx  adheres  to  its  walls  ; 
when  no  such  adhesion  occurs,  the  fruit 
or  ovarium  is  said  to  be  superior.  So, 
also,  the  calyx  is  called  superior  in  the 
former  case,  and  inferior  in  the  latter. 
French  botanists  employ  in  the  same 
sense,  and  with  much  greater  precision, 
the  terms  adherent  and  non-adherent. 

INFERIOR  VALVE.  That  valve  of 
adherent  bivalves  by  which  they  are 
united  to  other  substances. 

I'NFERO-BRANCHIATA  {inferus, 
beneath,  branchice,  gills).  An  order  of 
Aquatic  Gasteropods,  in  which  the  bran- 
chiae resemble  two  long  rows  of  leaflets, 
placed  on  the  two  sides  of  the  body, 
under  a  projecting  edge  formed  by  the 
mantle.  Cuvier  records  two  genera,  viz. 
phyllidia  and  diphyllidia. 

INFIMA  SPECIES.  In  Logic,  the 
lowest  species,  or  that  which  is  not  sub- 
divided, except  into  individuals.  See 
Species. 

FNFINITE  {infinitus,  boundless).  In 
Geometry,  an  infinite  quantity  is  that 
which  is  greater  than  any  assignable  mag- 
nitude ;  in  other  words,  it  is  an  abstrac- 
tion of  the  mind,  formed  by  excluding 
the  idea  of  limitation.  On  the  same 
principle,  an  infinitely  small  quantity  is 
a  quantity  considered  as  less  than  any 
assignable  magnitude.  Such  a  quantity 
is  called  an  infinitesimal,  and  the  em- 
ployment of  such  quantities  as  aux- 
iliaries, in  investigating  the  relations  of 
proposed  quantities,  is  called  the  infinite- 
simal analysis. 

INFFNITIVE  MOOD  (infinitus,  un- 
defined). In  Grammar,  that  condition  of 
the  verb  which  expresses  the  state  of  an 
action,  as  in  progress  or  completed,  but 
without  specification  of  person,  number, 
or  time. 

INFLAMMABLE    AIR.      Hydrogen 
gas,  named  from  its  highly  inflammable 
180 


nature.  It  was  formerly  called  phlogis- 
ton, from  its  having  been  considered  the 
matter  of  heat. 

INFLE'XION  (infiecto,  to  bend  in). 
In  Grammar,  any  change  made  in  a  word 
in  order  to  modify  its  meaning  is  called 
its  accident  or  inflexion.  Thus,  the  words 
Ccesar's,  legions,  were,  feared,  are  said  to 
be  inflected  forms,  or,  simply,  inflexions 
of  the  words  Caesar,  legion,  was,  and 
fear.  Inflexion  must  not  be  confounded 
with  termination  ;  it  denotes  any  change 
which  takes  place  in  a  word  between  the 
root  and  the  termination. 

INFLEXION  OF  WAVES.  If  a  cir- 
cular wave  of  a  non-elastic  fluid  impinge 
on  a  solid  in  which  there  is  an  aperture, 
that  part  of  the  wave  which  comes  against 
the  aperture  will  pass  freely  through, 
while  the  other  part,  which  strikes 
against  the  solid,  will  be  curved  about 
the  edges  of  the  aperture,  so  that  one 
semicircle  will  be  in  front  of  the  aper- 
ture, and  the  other  beyond  it.  This  is 
the  inflexion  of  waves.  The  new  circular 
waves  formed  about  the  aperture  will  in- 
tersect the  original  wave  and  each  other, 
so  that  interference  points  and  lines  will 
be  produced.  Similar  phenomena  occur 
in  waves  of  sound. 

INFLORESCENCE  ( infloresco,  to 
flourish).  A  term  expressing,  generally, 
the  arrangement  of  flowers  upon  a  branch 
or  stem.  The  various  forms  of  centri- 
petal inflorescence,  which  have  received 
distinct  appellations,  are  usually  referred 
to  modifications  of  the  spike  and  of  the 
raceme.  The  centrifugal  inflorescence  is 
represented  by  the  cyme. 

INFORMED  STARS.  Stars  which  are 
not  included  in  any  of  the  constellations. 

INFUNDIBU'LIFORM  {infundibu- 
lum,  a  funnel,  forma,  likeness).  Funnel- 
shaped  ;  a  term  applied  to  an  organ 
which  has  an  obconical  tube  and  an 
enlarged  limb,  as  the  corolla  of  tobacco. 

INFUSO'RIA  {infundo,  to  pour  in). 
Water  animalcules  ;  microscopic  animals 
found  in  infusions  of  animal  and*vege- 
table  matter.  They  are  distinguished 
into  the  Polygastrica  and  the  Motif  era. 

IN'GRESS  {ingressus,  an  entering). 
The  entering  of  the  sun  into  any  of  the 
twelve  signs,  or  other  parts  of  the  zodiac. 

INNATE  (innatus,  grown  upon). 
Growing  upon  any  thing  by  its  end ;  as 
applied,  in  Botany,  to  the  anther  when 
it  is  attached  by  its  base  to  the  apex  of 
the  filament. 

INNOVATIONS.  A  term  applied,  in 
Botany,  to  shoots  \»  hich  have  not  com- 


INS 


I  NT 


pleted  their  growth,  especially  those  of 
mosses. 

INOPE'RCULAR  (in,  not,  operculum, 
a  lid).  A  term  applied  to  univalve  shells 
which  have  no  operculum  or  lid. 

INOSCULATION  (in,  and  osculum, 
a  little  mouth).  The  union  of  vessels,  or 
anastomosis :  the  latter  term,  however,  is 
sometimes  used  to  designate  union  hy 
minute  ramification  ;  the  former,  a  direct 
communication  of  trunks. 

INSCRIBED  FIGURE.  In  Geome- 
try, a  circle  is  said  to  he  inscribed  in  a 
triangle  or  a  polygon,  when  it  touches  all 
the  sides  of  these  figures.  A  triangle  or 
a  polygon  is  said  to  be  inscribed  in  a 
circle,  when  all  the  angles  of  the  former 
figures  touch  the  circumference  of  the 
latter. 

INSE'CTA  (insecius,  divided  into  seg- 
ments). Insects ;  a  class  of  articulated 
animals  with  six  feet,  which  breathe  by 
tracheae,  have  a  dorsal  vessel  for  circu- 
lation, one  pair  of  antennae,  compound 
eyes,  generally  pass  through  a  distinct 
metamorphosis  and  acquire  wings,  and 
are  oviparous  with  the  sexes  distinct 
Burmeister  divides  them  as  follows  : — 

1.  Insecta  ametabola.  Insects  which 
do  not  undergo  metamorphosis.  The 
larva  resembles  the  perfect  insect,  but 
is  without  wings.  The  pupae  of  such 
species  as  have  wings  in  their  imago 
state  possess  rudiments  of  those  organs. 
The  pupa  runs  about  and  eats.  To  this 
division  belong  the  orders  Hemiptera, 
Orthoptera,  and  Dictyoptera. 

2.  Insecta  metabola.  Insects  which 
undergo  metamorphosis.  The  larva  is  a 
worm  either  with  or  without  legs.  The 
pupa  is  quiet ;  or,  if  it  moves,  it  does  not 
eat.  To  this  division  belong  the  orders 
Neuroptera,  Diptera,  Lepidoptera,  and 
Coleoptera. 

INSECTI'VORA  {insecta,  insects, 
voro,  to  devour).  A  group  of  mammi- 
ferous  animals,  considered  by  Cuvier  as 
a  family  of  the  great  carnivorous  order, 
and  characterized  by  their  molar  teeth 
being  studded  with  sharp  points,  which 
enables  them  to  devour  insect  prey. 
They  comprise  the  mole,  the  hedgehog, 
the  shrew,  &c. 

INSEPARABLE  ACCIDENT.  A 
logical  accident,  which  cannot  be  sepa- 
rated from  the  individual  to  which  it 
belongs,  though  it  may  from  the  species, 
as  for  a  person  to  be  a  native  of  London. 
See  Accident. 

INSESSO'RES  {insideo,  to  sit  upon). 
Perchers;  an  order  of  Birds,  the  foot 
181 


of  which  is  especially  formed  for  grasping 
or  perching— a  peculiarity  evinced  by  the 
situation  of  the  hinder  toe,  which  is 
invariably  placed  on  the  same  level  or 
plane  as  those  in  front. 

INSOLATION  (in,  and  sol,  the  sun). 
A  term  sometimes  employed  to  denote 
exposure  to  the  sun  for  the  purpose  of 
promoting  the  chemical  action  of  one 
substance  upon  another. 

INSOLUBILITY  (in,  not,  solvo,  to 
loose),  A  property,  resulting  from  co- 
hesion, by  which  a  substance  resists  so- 
lution. 

INSPISSATION  (in,  and  spissatus, 
thickened).  The  process  of  making  a 
liquid  of  a  thick  consistence. 

INSTANCES,  PREROGATIVE.  Un- 
der this  term  Lord  Bacon  cites  all  those 
instances,  or  facts,  which  have  a  chief 
claim  to  be  noticed  in  the  attempt  to  in- 
terpret the  laws  of  nature.  He  distributes 
them  into  three  classes,  viz.  those  which 
address  themselves  to  the  understanding, 
those  which  assist  the  senses,  and  those 
which  conduce  to  practice. 

INSTINCT.  The  spontaneous  impulse 
by  which  animals  perform  certain  ac- 
tions. Under  this  term  should  be  dis- 
tinguished the  instinctive  faculty,  which 
leads  the  duckling,  untaught,  into  the 
water,  and  the  chick,  untaught,  to  avoid 
the  water ;  and  the  instinctive  motions, 
or  those  involuntary  actions  which  are 
excited  mediately  through  the  nerves,  as 
the  closing  of  the  eye-lids,  the  act  of 
swallowing,  &c. 

INSULATION  (insula,  an  island).  A 
metaphorical  term  applied  to  a  body  con- 
taining a  quantity  of  electric  fluid,  and 
surrounded  by  non-conductors,  so  that  it 
is  insulated,  or  its  communication  with 
other  bodies  is  cut  off. 

INSU'RANCE.  A  per-centage  paid 
for  insuring  property  from  fire,  &c. 
When  the  charge  is  settled  for  any  kind 
of  property,  it  is  reckoned  per  cent,  upon 
the  whole  amount  of  it.  The  annual 
payment  is  called  the  premium,  and  the 
legal  document,  by  which  the  securer  is 
insured  from  loss  so  long  as  he  continues 
to  pay  the  premium,  is  called  the  policy 
of  insurance. 

I'NTEGER.  Literally  "  whole  ;»'  and, 
hence,  applied  in  arithmetic  to  a  whole 
number,  as  distinguished  from  a  fraction. 
INTEGRAL  CALCULUS.  That  branch 
of  mathematical  science  which  investi- 
gates the  processes  by  which  a  function 
may  be  found  such  that  its  differential 
shall  be  a  given  quantity.    It  was  for- 


INT 


INT 


merly  called  the  inverse  method  of  flux- 
ions; the  function  itself  was  called  the 
fluent,  or  flowing  quantity;  it  is  now 
termed  the  integral  or  sum  of  the  pro- 
posed differential. 

INTEGRAL  PARTICLES  (integer, 
entire).  The  most  minute  particles  into 
which  any  substance,  simple  or  com- 
pound, can  be  divided,  similar  to  each 
other,  and  to  the  substance  of  which  they 
are  parts.  Thus,  the  smallest  portion  of 
powdered  marble  is  still  marble  ;  but  if, 
by  chemical  means,  the  calcium,  the 
carbon,  and  the  oxygen  of  this  marble  be 
separated,  we  shall  then  have  the  ele- 
mentary or  constituent  particles. 

INTENSITY.  The  degree  or  rate  of 
the  power  or  energy  of  any  quality,  as  of 
heat  and  cold.  In  electricity,  it  denotes 
the  degree  to  which  a  body  is  electrically 
excited. 

INTENTION,  FIRST  and  SECOND. 
In  Logic,  the  "first  intention"  of  a  term 
is  a  certain  vague  and  general  significa- 
tion of  it,  as  opposed  to  one  more  precise 
and  limited,  which  it  bears  in  some  par- 
ticular art,  science,  or  system,  and  which 
is  called  its  "second  intention."  Thus, 
the  term  "bird"  in  its  first  intention 
signifies  any  individual  of  the  feathered 
tribes  ;  in  the  language  of  sportsmen,  or 
its  second  intention,  it  is  limited  to  the 
partridge. —  Whately. 

I'NTERAMBULA'CRA.  The  imper- 
forate plates  which  occupy  the  intervals 
of  the  perforated  plates,  or  ambulacra,  in 
the  shells  of  the  Echinoderms.  See  Am- 
bulacra. 

INTERCALATION.  The  insertion  of 
a  supernumerary  or  intercalary  day  into 
the  calendar  for  the  purpose  of  preserving 
the  account  of  time.     See  Calendar. 

INTERCE'LLULAR  SPACES.  Spaces 
existing  between  the  cells  and  other 
simple  tissues  of  plants. 

I'NTEREST.  The  consideration  paid 
for  the  use  of  money.  The  rate  of  in- 
terest is  the  sum  paid  for  the  use  of  a 
certain  sum  for  a  certain  time,  generally 
one  year.  The  sum  originally  lent  is 
called  the  principal;  the  principal,  to- 
gether with  its  interest  for  any  time,  is 
called  the  amount  for  that  time ;  the  prin- 
cipal is  also  called  the  present  value  of 
the  amount.  Interest  is  called  simple, 
when  it  is  paid  as  soon  as  due,  or  when, 
if  deferred,  interest  is  not  charged  on 
interest ;  when  the  latter  charge  is  made, 
the  interest  is  called  compound. 

INTERFERENCE.  A  term  applied, 
in  Optics,  to  certain  phenomena  occa- 
182 


sioned  by  the  mutual  action  of  the  rays 
of  light  on  one  other :  according  to  the 
distances  respectively  from  which  the 
rays  of  light  proceeding  from  two  lumi- 
nous points  fall  upon  the  same  spot,  the 
effect  is  diminished  or  increased ;  and  it 
is  this  mutual  action  which  is  called 
interference. 

INTERJE'CTION.  A  sound  uttered 
under  the  impulse  of  strong  emotion. 
Interjections  are  indeclinable,  stand  in 
no  close  connexion  with  the  sentences  in 
which  they  occur,  and  cannot  be  properly 
considered  as  a  distinct  part  of  speech. 

INTERMEDIATE.  A  term  applied 
to  a  third  substance,  employed  for  com- 
bining together  two  other  substances ; 
thus,  alkali  is  an  intermediate  between 
oil  and  water,  forming  soap. 

FNTERNODE  (inter,  between,  nodus, 
a  node  or  knot).  Merithallus.  That  por- 
tion of  the  stem  of  a  plant  which  occurs 
between  two  nodes. 

INTERPOLATION.  This  term  de- 
notes, simply,  the  insertion  of  something 
into  original  matter.  In  Algebra  and 
Astronomy,  it  is  a  method  adopted  for 
filling  up  the  intermediate  terms  of  a 
series  of  numbers  or  observations,  by 
numbers  which  follow  the  same  law. 

INTERROGATION,  FALLACY  OF. 
A  logical  fallacy,  which  may  be  referred 
to  the  head  of  "  Ambiguous  Middle."  It 
consists  in  asking  several  questions  which 
appear  to  be  but  one ;  so  that  whatever 
one  answer  is  given,  being  of  course  ap- 
plicable to  one  only  of  the  implied  ques- 
tions, may  be  interpreted  as  applied  to 
the  other.  The  refutation  is,  to  reply 
separately  to  each  question,  i.  e.  to  detect 
the  ambiguity. 

INTERRUPTED.  A  term  denoting 
a  disturbance  of  a  normal  arrangement. 
A  leaf  is  said  to  be  interruptedly  pinnate, 
when  some  of  the  pinnae  are  much  smaller 
than  the  rest,  or  absent. 

INTERSCE'NDENT.  A  term  applied 
by  Leibnitz  to  those  algebraical  quan- 
tities of  which  the  exponents  of  their 
powers  are  irrational ;  the  term  denotes 
their  holding  an  intermediate  place  be- 
tween algebraic  and  transcendental  quan- 
tities. 

INTERVAL,  MUSICAL.  A  term 
applied  to  a  certain  relation  between 
musical  notes,  which  depends  on  the 
number  of  their  vibrations.  The  sim- 
plest or  most  consonant  interval  is  that 
of  the  octave,  in  which  the  higher  note 
makes  twice  as  many  vibrations  as  the 
fundamental  note  from  which  it  is  de- 


IN  U 


IOD 


rived ;  its  ratio  is  that  of  1  ;  2  ;  4  '.  8, 
&c.  Compound  intervals  are  those  which 
exceed  an  octave,  and  they  are  named 
according  to  the  distance  of  the  two 
boundary  notes. 

INTERVE'NIUM  (inter,  between, 
vena,  a  vein).  That  portion  of  the  par- 
enchyma of  leaves,  which  lies  between 
two  or  more  veins  or  veinlets. 

INTESTI'NA.  An  order  of  worms 
which  inhabit  the  bodies  of  other  ani- 
mals. They  are  distinguished  by  Cuvier 
into  the  Cavitaria,  which  have  cavities 
or  stomachs;  and  the  Par en chymata,  or 
cellular-bodied,  as  the  tape-worm. 

INTE'XINE.  That  coating  of  the 
pollen-grain  which  is  situated  next  to 
the  extine,  constituting  a  fourth  layer  of 
the  pollen-grain  in  certain  plants. 

I'NTINE.  The  inner  coat  of  the  shell 
of  the  pollen-grain  in  plants.  See  Ex- 
tine. 

I'NTROIT  (introitus,  an  entering  in). 
A  term  employed  in  ancient  chronicles, 
signifying  the  first  two  or  more  words 
which  form  the  commencement  of  a 
mass,  which,  from  being  appropriated  to 
a  certain  Sunday,  or  other  festival,  gave 
the  name  of  such  commencement  or 
"  introit "  to  those  days.  Thus,  the  term 
"  adorate  Dominum"  is  the  introit  and 
name  of  the  third  Sunday  after  the  Epi- 
phany. 

INTRO'RSE  (introrsus,  qu.  intro- 
versus,  inwardly).  Turned  inwards;  as 
the,  anthers  of  plants  in  which  the  line  of 
dehiscence  is  towards  the  axis  of  the 
flower.     See  Extrorse. 

INTUITION  (intueor,  to  look  into). 
That  simple  faculty  of  the  mind  by 
which  we  immediately  perceive  the 
agreement  or  disagreement  of  two  ideas. 
In  this  the  mind  is  at  no  pains  of  proving 
or  examining,  but  perceives  the  truth  as 
the  eye  does  the  light,  only  by  being 
directed  to  it.  Intuitive  truth  has  ac- 
cordingly been  defined  as  that  "  which  is 
perceived  immediately  on  a  bare  atten- 
tion to  the  ideas  under  review." 

INTUS-SUSCEPTION  (intus,  within, 
suscipio,  to  receive).  The  inversion  of  a 
part  of  a  tube  within  a  contiguous  part. 
When  it  takes  place  downwards,  it  may 
be  termed  progressive ;  when  upwards, 
retrograde.  The  term  intussusception  is 
also  applied  to  the  process  of  nutrition, 
or  the  transformation  of  the  components 
of  the  blood  into  the  organized  substance 
of  the  various  organs. 

I'NULIN.  A  starch-like  substance 
which  is  spontaneously  deposited  from  a 
183 


decoction  of  the  root  of  the  Inula  Hele- 
nium,  or  Elecampane. 

INVAGINATION  {in,  in,  vagind,  a 
sheath).  A  sheathing  of  one  part  within 
another ;  a  term  synonymous  with  intus- 
susception. 

INVARIABLE.  In  Mathematics,  a 
term  synonymous  with  constant,  and 
applied  to  a  quantity  which  is  absolutely 
invariable.  It  may  also  denote  a  func- 
tion which  is  not  absolutely  invariable, 
but  which  does  not  vary  in  the  processes 
required  by  a  given  equation. 

INVE'NTION.  A  term  frequently 
confounded  with  discovery,  which  simply 
means  the  finding  out  something  already 
existing.  Invention,  however,  includes 
conception,  and  relates  to  the  mental 
operation  by  which  obj  cts  are  selected 
and  arranged  with  reference  to  a  parti- 
cular result.  The  polarity  of  the  magnet 
was  discovered ;  its  application  to  navi- 
gation was  invented  :  the  binomial  theory 
was  a  discovery  ;  the  method  of  fluxions 
an  invention. 

INVERTEBRA'TA.  A  negative  and 
unsatisfactory  term  by  which  Lamarck 
designated  all  those  animals  which  are 
not  furnished  with  a  vertebral  column 
or  backbone. 

INVOLU'CRUM  (involvo,  to  wrap  in). 
In  Botany,  a  whorl  of  bracts  which  sur- 
round several  flowers,  as  in  composite 
and  umbelliferous  plants.  In  the  latter 
family,  the  bracts  which  surround  the 
general  umbel  are  called  the  universal 
involucrum  ;  and  those  which  surround 
the  umbellules,  a  partial  involucrum,  or 
involucellum. 

I'NVOLUTE.  That  kind  of  curve 
which  is  described  by  the  extremity  of  a 
cord  as  it  is  unrolled  from  the  arc  of 
another  curve  about  which  it  has  been 
lapped,  the  latter  being  called  the  evolute. 
The  two  may  be  described  as,  the  curve 
unrolled,  and  the  curve  from  which  it  is 
unrolled.     See  Curve. 

INVOLUTION  (in  Algebra).  The 
process  of  finding  the  powers  of  quan- 
tities. The  examples  of  involution  are, 
therefore,  only  examples  of  multiplica- 
tion where  the  factors  are  all  the  same. 
See  Evolution. 

FODINE  (lw5^r,  or  loetdrj?,  violet- 
coloured,  from  'iov,  a  violet,  and  ei3or, 
likeness).  A  non-metallic,  crystallized, 
solid  substance,  found  in  marine  plants, 
in  the  ocean,  and  in  mineral  springs  ;  it 
becomes  volatile  by  a  slight  increase  of 
temperature,  and  forms  a  beautiful  violet 
vapour. 


IRO 


ISO 


1.  Iodal  (iodine  and  alcohol).  An  ole- 
aginous liquid  obtained  by  the  action  of 
iodine  upon  nitric  alcohol. 

2.  Iodic  Acid.  An  anhydrous  acid, 
termed  oxiodine  by  Davy,  and  produced 
by  the  combination  of  iodine  with  oxy- 
gen. It  combines  with  metallic  oxides, 
and  forms  salts  which  are  termed 
iodates. 

3.  Iodides,  or  Iodurets.  The  compounds 
of  iodine  with  metals,  and  with  the  sim- 
ple non-metallic  substances. 

4.  Iodous  Acid.  A  compound  prepared 
by  the  action  of  iodine  on  chlorate  of 
potash, — probably  by  the  combination  of 
iodine  and  chlorine. 

5.  Chloriodic  Acid.  This  is  also  called 
chloride  of  iodine ;  and  is  formed  by  the 
absorption  of  chlorine  by  dry  iodine. 

POLITE.  A  variety  of  quartz,  inter- 
mediate in  colour  between  violet-blue 
and  blackish-blue,  occurring  in  primitive 
rocks  in  Finland. 

FON  (iov,  that  which  goes  ;  neut.  part, 
of  elm,  to  go).  A  term  introduced  by 
Faraday,  explanatory  of  his  views  of 
electrolysis.  He  is  of  opinion  that  the 
force  does  not  emanate  from  the  poles  of 
the  battery,  but  that  it  resides  in  the 
substance  undergoing  decomposition,  of 
which  one  element,  or  ion,  goes  to  the 
positive,  the  other  element,  or  ion,  to  the 
negative,  end  of  the  battery.  The  ion 
which  goes  to  the  anode,  or  positive  pole, 
he  terms  an-ion ;  that  which  goes  to  the 
kathode,  or  negative  pole,  kat-ion.  See 
Electrode. 

IRIDA'CE^.  The  Cornflag  tribe  of 
Monocotyledonous  plants,  represented  by 
the  iris  and  the  crocus.  Smooth  herba- 
ceous plants,  with  leaves  ea^mtant',  flowers 
hexapetalous,  triandrous;  stamens  3; 
ovarium  3-celled,  many-seeded. 

IRIDE'SCENT  (iris,  a  rainbow).  The 
property  of  shining  with  many  colours, 
like  the  rainbow. 

IRIDINI'NjE.  A  sub-family  of  the 
Unionidcs,  or  River  Mussels,  named 
from  the  genus  iridina. 

IRI'DIUM  {iris,  a  rainbow).  The 
most  infusible  of  all  known  metals, 
named  from  the  variety  of  colours  it  dis- 
plays while  dissolving  in  hydro-chloric 
acid. 

IRON.  The  most  abundant  of  the 
true  metals,  occurring  in  the  form  of 
oxides  and  clay  iron-ore,  and  entering 
into  the  composition  of  many  rocks, 
which  frequently  owe  their  grey  colour 
to  it. 

Cast  or  pig  iron  is  the  name  given  to 
184 


the  metal  when  first  extracted  from  its 
ores.  Its  varieties  are  the  white  cast 
iron,  which  is  extremely  hard  and 
brittle,  and  appears  to  consist  of  small 
crystals ;  grey  or  mottled  cast  iron,  so 
called  from  the  inequality  of  its  colour, 
softer  and  less  brittle  than  the  preceding ; 
and  black  cast  iron,  the  most  unequal 
in  its  texture,  and  least  cohesive  of  the 
three. 

IRON-PYRITES.  Yellow  sulphuret 
of  iron.  An  ore  of  iron,  of  a  brass-yellow 
or  greenish-yellow  colour,  compact  or 
fibrous,  emitting  a  sulphurous  smell 
when  struck ;  granulated,  or  even  earthy, 
when  impure. 

IRONSTONE.  A  stratum  of  the  coal- 
formation,  forming  thin  beds,  or  disposed 
in  globular  or  depressed  masses,  alter- 
nating with  layers  of  shale.  It  is  of  a 
brown  or  grey  colour,  and  is  principally 
composed  of  iron  combined  with  oxygen, 
carbonic  acid,  and  water,  usually  with  a 
little  alumina,  silica,  and  lime. 

IRRA'TIONAL  NUMBERS.  A  terra 
applied,  in  Algebra,  to  those  numbers  or 
quantities,  the  roots  of  which  are  incom- 
mensurable by  unity,  and  the  exact  value 
of  which  can  therefore  never  be  deter- 
mined ;  in  other  words,  to  those  num- 
bers or  quantities  which  are  inexpres- 
sible by  an  arithmetical  ratio,  and  are 
therefore  "  arithmetically  irrational." 
These  numbers  are  generally  called 
surds,  from  the  Latin  surdus,  deaf  or 
senseless. 

IRREDU'CIBLE  CASE.  An  alge- 
braical term,  applied  to  that  class  of 
cubic  equations  in  which  Cardan's  for- 
mula fails  in  its  application.  The  reason 
of  the  failure  arises  from  the  imaginary 
expression  of  the  formula,  and  from  the 
fact  that  the  cubic  equations  in  question 
have  all  the  three  roots  real. 

IRREGULAR  BIVALVES.  Those 
bivalves  which  are  not  uniform  in  shape 
throughout  the  species ;  a  deviation  al- 
most confined  to  the  perforating  groups. 

IRREGULAR  MASSES.  A  term 
applied  by  MacCulloch  to  rocks  of  no 
determinate  form,  and  of  any  size,  as 
granite,  greenstone,  and  porphyry. 

FSERINE.  An  iron-black  mineral, 
containing  titanium  aod  uranium,  found 
near  the  origin  of  the  river  Iser,  dis- 
seminated in  granite  sand,  and  in  allu- 
vial soil,  together  with  pyrope,  in  Bo- 
hemia. 

ISO-  (tVof,  equal).  This  prefix  denotes 
equality,  or  similarity.     Hence,— 

1.  Iso-barysm  (fidpos,  weight).    Simi- 


ISO 

larity  of  weight,  supposed  to  be  the  cause 
of  the  identity  in  the  size  and  shape  of 
molecules  which  cohere  into  the  crystal- 
line form. 

2.  Iso-bryous  {/3pvia,  to  grow).  That 
which  grows  equally ;  a  term  applied  by 
some  writers  to  dicotyledonous  plants, 
which,  having  two  cotyledons,  grow  with 
equal  force  on  the  two  sides  of  the  axis. 
For  the  same  reason,  such  plants  have 
been  called  iso-dynamous,  from  dt/va/ui?, 
force.     See  Anisobryous. 

3.  Iso-chromatic  (xpw/ua,  colour).  Hav- 
ing the  same  colours,  as  applied  to 
lenses.  The  light  which  is  decomposed 
by  doubly  refracting  crystals,  forms  a 
double  series  of  coloured  curves  of  dif- 
ferent forms,  arranged  in  a  different  order, 
each  curve  in  the  one  series  having  a 
curve  corresponding  to  it  in  form  and 
colour  in  the  other.  The  two  curves 
which  have  the  same  tint,  are  called  iso- 
chromatic. 

4.  Iso-chronous  (xpovor,  time).  That 
which  occurs  in  equal  times  ;  as  the 
strokes  of  the  pulse,  the  vibrations  or 
oscillations  of  pendulums  of  the  same 
length,  &c.  Hence,  the  term  isochron- 
ism  is  applied  to  that  property  of  all  sys- 
tems which  are  in  equilibrio,  by  which 
the  retardation  or  acceleration  of  the 
oscillations  is  not  perceptibly  influenced 
by  any  disturbing  force. 

5.  Iso-clinic  Lines  (nXivat,  to  incline). 
Lines  of  equal  inclination  or  dip ;  a  term 
applied  to  curves  which  connect  those 
places  in  the  two  hemispheres  where  the 
dip  of  the  magnetic  needle  is  equal ;  they 
surround  the  globe,  running  nearly  paral- 
lel with  the  magnetic  equator.  These 
curves  coincide  in  position  with  the  iso- 
thermal lines.    See  Aclinic  Line. 

6.  Iso-cyclous  (kukAoc,  a  circle).  A 
term  applied  to  animals  which  are  com- 
posed of  a  succession  of  equal  rings,  as 
some  of  the  Crustacea. 

7.  Iso-dynamic  Lines  (hvvayus,  power). 
Lines  of  equal  power;  a  term  applied  by 
Hansteen  to  lines  which  connect  those 
places  where  the  intensity  of  the  terres- 
trial magnetism  has  been  found  to  be 
equal,  and  which  resemble  in  form  and 
position  the  isoclinic  lines,  though  they 
approach  still  more  nearly  to  the  iso- 
thermal lines. 

8.  Iso-gonic  Lines  (ywvia,  an  angle). 
Lines  of  equal  declination  ;  a  term  ap- 
plied to  lines  connecting  those  places 
which  have  an  equal  declination  west  or 
east.  Most  of  these  lines  are  drawn 
around  two  points  near  to  the  north  and 

185 


ISO 

south  poles  of  our  planet,  called  the 
magnetic  poles  of  the  earth,  or,  more  cor- 
rectly, magnetic  poles  of  convergence. 

9.  Iso-merism  {fiepot,  part).  A  term  in 
chemistry  expressive  of  the  relation  ex- 
isting becween  bodies,  which  agree  in 
composition  but  differ  in  properties.  Iso- 
meric bodies  have  in  general  been  found 
to  agree  in  the  relative  proportion  of 
their  constituents  only,  and  to  differ 
either  in  the  aggregate  number  of  the 
atoms  composing  them,  or  in  the  mode 
of  arrangement  of  these  atoms.  Berze- 
lius  has  employed  three  terms  to  in- 
clude the  different  cases  of  these 
bodies,  viz.  isomeric,  polymeric^  and  meta- 
meric. 

10.  Iso-morphism  {^opcptj,  form).  A 
term  in  chemistry  applied  by  Mitscherlich 
to  the  relation  in  form  which  exists  in 
different  bodies,  as  a  general  consequence 
of  similarity  of  composition.  The  law 
at  which  he  arrived  is  as  follows  :— The 
same  number  of  atoms  combined  in  the 
same  way  produce  the  same  crystalline 
form ;  and  crystalline  form  is  independent 
of  the  chemical  nature  of  the  atoms,  and 
determined  only  by  their  number  and 
relative  position. 

11.  Iso-morphous  (fxop<ptj,  form).  A 
term  applied  to  some  groups  of  chemical 
substances,  which,  having  the  same 
crystalline  form,  are  found  to  enter  into 
analogous  combinations,  which  also  re- 
spectively present  the  same  form ;  and  to 
some  other  groups  which  have  been  ob- 
served to  enter  into  similar  combinations, 
having  very  similar  crystalline  charac- 
ters. Of  these  iso-morphous  bodies,  the 
salts  of  phosphoric  and  arsenic  acids 
afford  remarkable  examples. 

12.  Iso-perimetrical  (irepifxeTpov,  cir- 
cumference). Having  the  same  length 
of  perimeter,  circumference,  or  bounding 
line.  Of  all  iso-perimetrical  figures,  that 
is  the  greatest,  which  contains  the  most 
sides  or  angles ;  hence,  the  circle  is  the 
most  capacious  of  all  iso-perimetrical 
figures. 

13.  Iso-poda  (wove,  vrodo?,  a  foot).  A 
group  of  crustaceous  animals,  which  have 
seven  pairs  of  similar  unguiculate  feet, 
attached  to  seven  moveable  segments 
behind  the  cephalic.  A  characteristic 
example  is  found  in  the  oniscus,  or  wood- 
louse. 

14.  Iso-pyre.  A  new  mineral  found  in 
Cornwall,  imbedded  in  granite;  it  re- 
sembles obsidian,  or  even  some  varieties 
of  iron  slag. 

15.  Isosceles   (<rxe\of,    a   leg).     The 


JET 


JUL 


designation  of  a  triangle  of  which  two 
sides,  or  legs,  are  equal. 

16.  Iso-stemonous  ((tt^juwv,  a  stamen). 
A  term  applied  by  De  Candolle  to  those 
plants,  the  stamens  of  which  are  equal  in 
number  to  the  petals.  See  Anisostemonous. 

17.  Iso-thermal  Lines  (04p/j.n,  heat). 
Lines  of  equal  temperature ;  a  term  ap- 
plied, in  physical  geography,  to  lines  con- 
necting all  those  places  on  the  surface  of 
the  Globe  which  have  the  same  mean 
temperature.  Lines  drawn  through  places 
having  the  same  summer,  and  the  same 
winter  temperatures,  are  termed,  respec- 


tively, iso-theral  (0<?por,  summer),  and 
iso-cheimal  (xe»Ma>  winter)  lines ;  while 
lines  drawn  through  places  having  other 
common  temperatures,  receive  other  ap- 
propriate names. 

I'STHMUS.  A  narrow  neck  of  land 
lying  between  two  seas,  and  connecting 
two  masses  of  land  greater  than  itself. 

ITACONIC  ACID.  Another  name 
for  the  pyrocitric  or  citricic  acid. 

I'TTNERITE.  A  rare  mineral,  con- 
sisting chiefly  of  silica,  alumina,  and 
soda,  together  with  some  hydrosulphu- 
ret ;  named  after  Ittner. 


JACULATRI'CES  (jaculum,  a  dart). 
The  name  given  by  Macgillivray  to  an 
order  of  birds,  from  the  peculiar  form  of 
their  bill,  and  their  rapid  flight.  The 
families  composing  the  order  are  the 
Alcedinae,  the  Galbulinae,  and  the  Tro- 
goninae,  of  which  the  last  two  have  the 
feet  zygodactyle. 

JADE.  Nephrite.  A  mineral  sub- 
stance found  in  granite  and  gneiss,  in 
Switzerland,  and  divisible  into  the  two 
varieties  of  common  nephrite  and  ama- 
zonian  stone.  The  name  has,  however, 
been  applied  to  various  minerals  which 
resemble  one  another  in  little  else  than 
in  colour. 

JA'MESONITE.  A  mineral  consist- 
ing principally  of  the  sulphurets  of  anti- 
mony and  of  lead,  and  named  after  Pro- 
fessor Jameson. 

JA'RGON.  Jargon  of  diamond  is  a 
designation  of  one  of  the  varieties  of 
zircon. 

JA'SPER.  A  siliceous  substance  of 
various  colours,  occurring  in  veins  in 
trap  rocks,  in  volcanic  rocks,  and  in  the 
primary  and  secondary  series. 

JATROPHIC  ACID.  Crotonic  Acid. 
An  acid  procured  by  the  saponification  of 
croton  oil. 

JE'FFERSONITE.  A  variety  of  py- 
roxene ;  a  new  mineral  found  in  Frank- 
linite  and  garnet,  in  New  Jersey. 

JE'RVINE.  A  vegeto-alkali,  found 
in  the  root  of  veratrum  album. 

JET,  or  PITCH  COAL.  A  black  vel- 
vet-coloured bitumen,  used  for  fuel,  and 
for  making  vessels,  &c.  In  Prussia  it 
is  called  black  amber,  and  is  cut  into 
rosaries  and  necklaces.  Ure  says  the 
186 


word  jet  is  derived  from  the  river  Gaga 
in  Lesser  Asia. 

JEWELLERS'  PUTTY.  Ignited  and 
finely-levigated  oxide  of  tin,  used  by 
jewellers  for  polishing  hard  objects. 

JOINTS.  In  Geology,  fissures  or  lines 
of  parting  in  rocks,  often  at  right  angles 
to  the  planes  of  stratification.  The  part- 
ings which  divide  columnar  basalt  into 
prisms,  are  joints. 

JU'DGMENT.  In  Logic,  an  operation 
of  the  mind,  by  which  we  compare  two 
ideas  or  notions  which  are  the  objects 
of  apprehension,  whether  complex  or 
incomplex,  and  pronounce  upon  their 
agreement  and  disagreement.  Judgment 
is,  therefore,  either  affirmative  or  nega- 
tive. 

JU'GUM.  The  Latin  term  for  a  yoke, 
and  hence  applied  to  a  pair  of  opposite 
leaflets  on  the  petiole  of  a  pinnate  leaf. 
Thus  a  leaf  with  one  pair  is  called  uni- 
jugal;  with  two  pairs,  bijugal,  &c. 

Juga  in  Umbelliferous  Plants.  The 
term  juga  also  signifies  ridges,  and  is 
hence  applied  to  the  elevated  portions  by 
which  the  carpels  of  umbelliferous  plants 
are  traversed;  of  these  juga,  five  are 
called  primary,  and  four,  alternating 
with  them,  secondary. 

JULIAN  CALENDAR.  The  mode 
of  reckoning  the  divisions  of  the  year, 
adopted  by  Julius  Caesar,  and  afterwards 
corrected  by  Gregory  XIII.  It  is  ex- 
plained under  the  term  Bissextile.  The 
Russians  still  retain  the  Julian  style, 
and  their  year  consequently  begins  twelve 
days  later  than  ours. 

JULIAN  PERIOD.  A  revolution  of 
7980   years,  reckoned  from   4713  years 


K  AL 


KEE 


before  our  era,  and  produced  by  the 
continued  multiplication  of  the  solar 
cycle,  the  lunar  cycle,  and  the  cycle  of 
indiction,  viz.  19,  28,  and  15.  See 
Cycle. 

JU'LIDiE.  The  lowest  division  of  the 
Myriapods,  so  named  from  the  julus,  or 
common  millepede. 

JUNGERMANNIA'CEiE.  An  order 
of  creeping  moss-like  plants,  named  from 
the  genus  jungermannia,  and  distin- 
guished from  several  allied  orders  by 
the  theca  opening  by  valves,  without  an 
operculum.  In  all  the  orders  the  spores 
are  mixed  with  elaters. 

JUNO.  A  telescopic  planet,  situated 
in  the  solar  system  between  Mars  and 
Jupiter,  and  said  to  be  1320  miles  in  dia- 
meter. Its  distance  from  the  sun  is 
about  256  millions  of  miles,  and  it  com- 
pletes its  revolution  in  4  years,  128  days. 


This  planet  was  discovered,  in  1804,  by 
Mr.  Harding  of  Bremen. 

JUPITER.  The  largest  of  the  planets, 
and,  next  to  Venus,  the  most  brilliant. 
It  is  1470  times  the  size  of  the  earth.  It 
completes  its  orbit  round  the  sun  in 
4332*596  days.  It  is  accompanied  by  four 
satellites. 

JURA  LIMESTONE.  A  term  applied 
to  the  limestones  belonging  to  the  Oolitic 
group,  and  constituting  the  chief  part  of 
the  mountains  of  the  Jura,  between 
France  and  Switzerland. 

JURA'SSIC  SYSTEM.  A  term  syn- 
onymous in  continental  writers  with  our 
Oolitic  System. 

JURISPRUDENCE.  General  juris- 
prudence is  the  science  or  philosophy  of 
positive  law,  as  distinguished  from  par- 
ticular jurisprudence,  or  the  knowledge 
of  the  law  of  a  particular  country. 


K 


KAKO'XENE.  A  crystalline  mineral, 
found  in  iron-stone,  in  Bohemia. 

KALEI'DOPHON  (»ca\6v,  beautiful, 
eldor,  form,  <t>u>vrj,  sound).  An  instru- 
ment, invented  by  Mr.  Wheatstone,  for 
exhibiting  the  vibrations  of  an  elastic 
rod.  If  a  rod  of  this  kind,  fastened  at 
one  end,  be  set  in  motion  by  a  blow,  or 
bending,  it  will  describe  paths  which  do 
not  always  lie  in  the  same  plane,  but 
return  in  variously-curved  lines.  If  the 
free  end  of  the  rod  be  surmounted  with 
a  polished  knob,  the  curves  will  be  exhi- 
bited in  a  beautiful  manner  to  the  eye. 

KALEIDOSCOPE  [na\6s,  beautiful, 
eidor,  form,  anoireoj,  to  see).  A  well- 
known  apparatus,  invented  by  Sir  D. 
Brewster,  by  which  the  image  of  an  ob- 
ject is  multiplied  by  repeated  reflections 
from  inclined  mirrors,  placed  opposite  to 
one  another. 

KALI.  A  term  of  Arabic  origin,  de- 
noting a  particular  plant ;  hence  the  word 
al-kali,  with  the  article,  originally  signi- 
fied the  particular  residuum  obtained  by 
lixiviating  the  ashes  of  that  plant;  the 
term  was  then  used  for  potassa. 

KA'LOTYPE  (»ca\6?,  beautiful,  two?, 
an  impression).  The  art  of  fixing  photo- 
graphic images  upon  surfaces  of  silver, 
first  suggested  by  Wedgewood,  and  sub- 
sequently improved  by  Daguerre  (See 
Daguerreotype).  Talbot  employs  for  this 
purpose  a  paper  which  is  rendered  pecu- 
187 


liarly  susceptible  to  light,  and  which  is 
termed  kalotype  paper ;  a  negative  pic- 
ture is  formed  upon  the  paper  in  the 
camera  obscura,  and  fixed  by  means  of 
bromide  of  potassium. 

KAOLIN.  China-clay;  a  fine  pure 
clay  prepared  by  levigation  from  moul- 
dering granite,  and  employed  in  the 
manufacture  of  porcelain. 

KA'RPHOLITE  (xdptfxK,  a  straw, 
Xi'tfor,  a  stone).  A  yellow  mineral,  oc- 
curring in  thin  prismatic  concretions. 

KARPHOSIDE'RITE  ( K<ip<t>os,  a 
straw,  <ribt)pos,  iron).  A  straw-coloured 
mineral,  resembling  iron-sinter,  and  oc- 
curring in  Labrador. 

KA'RSTENITE.  Another  name  for 
anhydrite,  or  prismatic  gypsum. 

KATHODE  {Kara,  downwards,  6d6s, 
a  way).  A  term  applied  by  Mr.  Faraday 
to  that  part  of  the  surface  of  a  decom- 
posing body  at  which  the  electricity  de- 
parts— the  part  immediately  touching  the 
negative  pole.    See  Anode. 

KA'TION  (koltiov,  that  which  goes 
down).  A  term  applied  by  Mr.  Faraday 
to  the  body  which  passes  to  the  negative 
pole,  or  kathode,  of  the  decomposing 
body,  as  it  is  separated  by  electricity. 
See  Anion. 

KEDRIA  TERRESTRIS.  Barbadoes 
tar ;  a  mineral  oil.     See  Bitumen. 

KEEL.  Carina.  A  term  applied  by 
botanical  writers  to  the  two  lower  petals 


KER 


KNO 


of  a  papilionaceous  corolla,  which  cohere 
by  their  lower  margins,  so  as  to  present 
a  keeled  or  boat-like  form. 

KEEPER  OF  A  MAGNET.  A  piece 
of  soft  iron,  which  is  placed  in  absolute 
contact  with  the  poles  of  a  magnet  when 
not  in  use.  The  keeper  tends,  by 
induction,  to  maintain,  and  even  exalt, 
the  power  of  the  magnet,  whose  poles  are 
thus  employed  in  producing  the  opposite 
magnetism  in  its  respective  ends. 

KE'LLOWAY  ROCK.  A  term  ap- 
plied to  beds  of  limestone  occurring  in 
the  lower  part  of  the  Oxford  or  Clunch 
clay ;  it  is  often  composed  of  irregular 
nodules,  and  is  sometimes  full  of  shells, 
among  which  predominate  ammonites 
and  large  gryphaeae. 

KELP.  Varec.  The  crude  soda  ob- 
tained from  the  ashes  of  the  Futi  in 
Holland  and  on  the  northern  coast  of 
France.  It  is  used  in  the  composition  of 
soap,  in  the  manufacture  of  alum,  and  in 
the  formation  of  crown  and  bottle  glass. 
See  Barilla. 

KEPLER'S  LAWS.  The  laws  of 
elliptic  motion  about  the  sun  as  a  focus, 
and  of  the  equable  description  of  areas 
by  lines  joining  the  sun  and  planets, 
were  originally  established  by  Kepler, 
from  a  consideration  of  the  observed  mo- 
tion of  Mars,  and  were  by  him  extended, 
analogically,  to  all  the  other  planets. 
These  laws  are  three  : — 

1.  That  every  planet  moves  so  that  the 
line  drawn  from  it  to  the  sun  describes 
about  the  sun  areas  proportional  to  the 
times. 

2.  That  the  planets  all  move  in  elliptic 
orbits,  of  which  the  sun  occupies  one  of 
the  foci. 

3.  That  the  squares  of  the  times  of  the 
revolutions  of  the  planets  are  as  the 
cubes  of  their  mean  distances  from  the 
sun. 

KERATO'PHYTA  (i«?par,  Keparo?, 
horn,  (pvTov,  a  plant).  An  old  name  for 
those  polyps  which  have  a  horny  axis,  as 
distinguished  from  the  lithophytes,  or 
strong  polyps. 

KERMES  ANIMAL.  Coccus  Ilicis. 
A  hemipterous  insect,  found  upon  the 
quercus  ilex,  and  formerly  used  for  dye- 
ing scarlet  :  cloth  so  dyed  was  called 
coccinum,  and  persons  wearing  this  cloth 
were  termed  by  the  Romans  coccinati. 
The  drug  was  termed  grana  kermes,  from 
the  resemblance  of  the  dried  insects  to 
grains  or  seeds. 

KERMES  MINERAL.  Formerly, 
Panacea  Glauberiana ;  a  sulphuret  of 
188 


antimony;  so  named,  from  its  resem- 
blance, in  colour,  to  the  insect  kermes. 

KEUPER.  A  Gennan  name  for  a 
member  of  the  Upper  New  Red  Sand- 
stone formation.  Remains  of  reptiles 
are  said  to  have  been  found  in  it  near 
Warwick. 

KEY  (in  Music).  The  particular  dia- 
tonic scale,  in  which  a  composition  begins 
and  ends,  and  which  prevails  more  or 
less  in  a  given  piece  of  music.  There 
are  twelve  major  and  twelve  minor  keys. 

KILLAS.  The  technical  name  ap- 
plied by  the  Cornish  miners  to  clay-slate, 
or  the  grauwacke  slate  of  other  countries. 

KI'LLINITE.  A  mineral  resembling 
spodumene,  discovered  in  granite  veins 
at  Killiney,  near  Dublin. 

KI'MMERIDGE  CLAY.  A  thick  bed 
of  clay,  constituting  a  member  of  the 
Oolitic  Group,  and  occurring  well  deve- 
loped at  Kimmeridge,  in  the  isle  of  Pur- 
beck,  Dorsetshire. 

KING'S  YELLOW.  A  paint,  of  which 
the  colouring  principle  is  orpiment,  or 
the  sesqui-sulphuret  of  arsenic. 

KINGDOM.  A  term  denoting  any  of 
the  principal  divisions  of  nature ;  thus 
we  have  the  organic  kingdom,  compre- 
hending substances  which  organize,  and 
the  inorganic  kingdom,  comprehending 
substances  which  crystallize. 

KINIC  ACID.  Quinic  acid.  An  acid 
found  in  the  Cinchona  barks.  It  forms 
salts  called  kinates. 

Kino'ile.  A  neutral  substance  pro- 
duced by  the  calcination  of  a  kinate  by 
a  gentle  heat. 

KITE,  ELECTRICAL.  An  appara- 
tus for  proving  the  existence  of  sensible 
electricity  in  the  atmosphere.  A  wooden 
rod,  of  several  feet  in  length,  fastened  by 
its  lower  end  to  a  glass  tube,  and  sur- 
mounted at  the  other  by  a  pointed  brass 
or  copper  wire,  forms  an  insulated 
conductor  to  attract  the  electricity.  A 
second  wire,  attached  to  the  first,  is  con- 
nected with  a  delicate  electrometer,  which 
exhibits  the  electricity  conducted  to  it 
from  the  atmosphere. 

KNE'BELITE.  A  grey  spotted  mine- 
ral, consisting  of  silica,  iron,  and  manga- 
nese. 

KNOWLEDGE.  "  Knowledge  implies 
three  things  ;  1st,  firm  belief;  2ndly,  of 
what  is  true ;  3rdly,  on  sufficient  grounds. 
If  any  one,  e.  g.  is  in  doubt  respecting 
one  of  Euclid's  demonstrations,  he  cannot 
be  said  to  know  the  proposition  proved  by 
it ;  if,  again,  he  is  fully  convinced  of  any 
thing  that  is  not  true,  he  is  mistaken  in 


LAB 


LAC 


supposing  himself  to  know  it ;  lastly,  if 
two  persons  are  each  fully  confident,  one 
that  the  moon  is  inhabited,  and  the  other 
that  it  is  not  (though  one  of  these  opi- 
nions must  be  true),  neither  of  them 
could  properly  be  said  to  know  the  truth, 
since  he  cannot  have  sufficient  proof  of 
it."—  Whately. 

KOBELL  S  DISCOVERY.  A  method 
proposed  by  Kobell  of  Munich  by  which 
pictures  drawn  in  bistre  or  Indian  ink 
may  be  multiplied  by  the  process  of  elec- 
trotype, or  gal  vano- plastics. 

KO'LLYRITE.  A  white  mineral 
found  in  porphyry,  in  Hungary. 

KO'NIGINE.    A  green  mineral,  pro- 


bably  consisting   of  a   subsulphate    of 

copper. 

4  KOUTHOLITE  {koZ<j>o?,  light,  \i9os, 

a  stone).    A  variety  of  prehnite  found 

near  Bareges. 

KRAME'RIC  ACID.  A  peculiar  sub- 
stance supposed  to  exist  in  the  root  of 
the  krameria  triandra. 

KUNDAH  Oil.  An  oil  obtained  from 
the  seeds  of  the  Carapa  Toulouconna, 
also  called  tallicoonah  oil. 

KUPFERN1CKEL.  The  German  name 
for  sulphuret  of  nickel,  in  which  the 
metal  is  generally  mixed  also  with  arse- 
nic, iron,  and  cobalt. 


LABA'RRAQUE'S  SOLUTION.  A 
disinfecting  liquid,  consisting  of  a  solu- 
tion of  the  chlorides  of  lime  and  of  soda. 
It  is  analogous  to  the  well-known  bleach- 
ing powder,  chloride  of  lime. 

LABE'LLUM  (dim.  of  labium,  a  lip). 
A  little  lip  ;  the  botanical  designation  of 
the  lip-like,  or  undermost,  petal  of  orchi- 
daceous plants. 

LABIA'TiE  {labium,  a  lip).  The  La- 
biate or  Mint  tribe  of  Dicotyledonous 
plants.  Herbaceous  plants,  with  leaves 
opposite ;  flowers  irregular,  unsymmetri- 
cal;  stamens  four,  didynamous,  inserted 
into  the  corolla ;  ovarium  deeply  4-lobed  ; 
fruit  1 — 4  small  nuts. 

LA'BIATE  {labium,  a  lip).  A  botani- 
cal designation  of  a  gamopetalous  calyx 
or  corolla,  which  is  separated  into  two 
unequal  divisions,  resembling  lips,  the 
one  anterior,  the  other  posterior,  with 
respect  to  the  axis.  Hence,  the  term  bi- 
labiate is  more  commonly  used.  This 
form  of  the  floral  envelopes  is  character- 
istic of  the  Mint  tribe.     See  Labiates. 

LA'BORATORY.  A  room  properly 
furnished  for  the  performance  of  chemical 
operations. 

LA'BRADOR  FELSPAR.  Labrador- 
ite.  A  species  of  felspar  found  chiefly  on 
the  coast  of  Labrador,  and  in  the  transi- 
tion syenite  of  Laurwig  in  Norway.  It 
is  also  called  opalescent  felspar,  from  its 
often  exhibiting  a  beautiful  play  of  co- 
lours in  cut  and  polished  specimens.  It 
is  probably  a  variety  of  albite. 

LA'BRID^E.  A  family  of  acantho- 
pterygious  fishes,  named  from  the  genus 
189 


labrus,  or  the  wrasse.  They  comprise 
the  Parrot-fishes,  so  remarkable  for  the 
convex  form  of  the  jaws. 

LAB  RUM.  Literally,  the  extremity 
of  the  lips ;  also,  the  brim  of  any  vessel. 
In  Entomology  it  is  applied  only  to  the 
lower  lip  of  insects. 

LABYRI'NTHODON  (KapvptvOot,  a 
labyrinth,  bbov?,  a  tooth).  The  name 
now  given  to  the  Cheirotherium,  a  sup- 
posed crocodilian  animal  of  considerable 
size,  to  which  have  been  referred  the 
singular  footsteps  found  impressed  on 
several  beds  of  marly  sandstone  in  va- 
rious parts  of  England  and  Europe, 
bearing  a  remarkable  resemblance  to  the 
human  hand.  The  present  name  is  de- 
rived from  the  complex  or  labyrinthine 
structure  of  a  section  of  the  tooth,  as 
seen  under  the  microscope. 

LAC  {laak,  Arab  ).  A  resinous  sub- 
stance, improperly  termed  a  gum,  depo- 
sited by  the  insect  coccus  lacca,  on  the 
leaves  and  branches  of  several  trees,  over 
its  eggs,  as  a  present  protection,  and  as  a 
future  food  for  the  maggot.  Stick-lac  is 
the  substance  in  its  natural  state,  en- 
crusting twigs ;  seed  lac  is  the  lac  sepa- 
rated from  the  twigs,  and  of  a  granulated 
form,  like  mustard  seeds  ;  shell- lac  is  the 
substance  obtained  after  purification  ; 
lump-lac  is  the  seed-lac  melted  and 
formed  into  cakes.  Lac-dye,  lac-lake, 
or  cake-lac,  are  designations  of  the  colour- 
ing matter  extracted  from  the  stick- 
lac. 

LAC  LUNiE.  Moon-milk;  a  snow- 
white  substance,  resembling  chalk,  and 


LAC 


L  AK 


consisting    almost    wholly   of  alumina, 
saturated  with  carbonic  acid. 

LACCIC  ACID.  An  acid  obtained 
from  stick-lac,  forming  salts  called  lac- 
cates. 

LACCIN.  A  principle  discovered  in 
lac,  intermediate  between  wax  and  resin. 

LACE'RTA.  The  Lizard;  a  modern 
northern  constellation,  consisting  of  six- 
teen stars.  It  is  surrounded  by  Andro- 
meda, Cepheus,  Cygnus,  and  Pegasus. 

LACERTI'NIDiE  {lacertus,  a  lizard). 
A  family  of  Saurian  reptiles,  including 
the  common  lizards  of  this  country,  and 
most  of  the  Saurians  of  active  habits. 
They  are  characterized  by  their  small 
head,  thick  neck,  and  long,  slender, 
forked  tongue. 

LACI'NIATED  (lacinia,  the  fringe  of 
a  garment).  A  term  applied,  in  Botany, 
to  those  leaves  which  are  divided  by 
deep,  taper-pointed  incisions.  Such 
leaves  are  also  said  to  be  slashed,  decom- 
posed, or  multifid.  The  inflexed  point 
of  the  umbelliferous  petal  is  called  the 
lacinula. 

LA'CQUER.  A  solution  of  shell-lac 
in  alcohol. 

LA'CTEALS  {lac,  lactis,  milk).  Mi- 
nute vessels  which,  in  the  animal  eco- 
nomy, absorb,  or  take  up,  the  chyle,  or 
milk-like  fluid,  from  the  alimentary  canal. 
See  Absorption. 

LACTIC  ACID  {lac,  lactic,  milk). 
An  acid  generated  whenever  milk,  and 
perhaps  most  animal  fluids,  become  spon- 
taneously sour,  or  when  the  juice  of  beet- 
root is  preserved  for  some  months  at  a 
high  temperature.  Its  salts  are  called 
lactates. 

LA'CTINE  {lac,  milk).  Saccholactin. 
Sugar  of  milk ;  obtained  by  evaporating 
the  whey  of  milk  to  crystallization,  and 
purifying  the  first  product  by  animal 
charcoal  and  a  second  crystallization. 

LACTO'METER  {lac,  lactis,  milk, 
fierpov,  a  measure).  A  graduated  glass 
tube,  for  ascertaining  the  relative  quan- 
tity of  cream  afforded  by  milk.  A  more 
correct  term  would  be  galactometer. 

LACTU'CIC  ACID.  An  acid  dis- 
covered in  the  juice  of  the  lactuca  virosa, 
or  wild  lettuce. 

LACU'NiE  {lacus,  a  lake).  A  term 
applied  by  Link  to  the  air-cells  which 
occur  in  the  tissue  of  plants.  In  lichens, 
they  are  the  small  hollows  or  pits  which 
occur  on  the  upper  surface  of  the  thallus ; 
and  hence  the  term  lacunose  is  applied  to 
a  body  which  has  large  deep  lacunae  or 
depressions  on  the  surface. 
190 


LACU'STRINE  {lacus,  a  lake).  Be- 
longing to  a  lake.  A  lacustrine  deposit 
consists  of  alluvial  matter  carried  down 
by  rivers  and  deposited  at  the  bottom  of 
lakes. 

LjEMODFPODA  {Xainot,  the  throat, 
nodes,  feet).  A  group  of  crustaceous 
animals,  which  have  the  anterior  pair  of 
feet  attached  to  the  cephalic  segment ; 
they  have  no  post-abdominal  branchiae ; 
the  eyes  are  sessile,  and  the  mandibles 
without  palpi.'  A  characteristic  example 
is  found  in  the  cyamus,  commonly  called 
the  whale-louse,  from  its  infesting  the 
cetacea  as  a  parasite. 

LAGOON  or  LAGUNE.  An  extensive 
sheet  of  shallow  water,  formed  either  by 
the  encroachment  of  the  sea  or  rivers 
upon  the  land,  or  by  the  separation  of  a 
portion  of  the  sea  by  the  intervention  of 
a  bank.  Thus,  there  are  fluvial  and 
marine  lagunes. 

LA'GRIID^E.  A  family  of  coleopte- 
rous insects,  of  the  section  Heteromera, 
named  from  the  genus  Lagria,  one  spe- 
cies of  which  is  indigenous  in  this  coun- 
try. 

LAKE.  An  insoluble  compound, 
formed  by  precipitating  colouring  matter 
with  an  earth  or  oxide.  The  principal 
lakes  are  carmine,  obtained  from  cochi- 
neal, by  precipitation  with  Roman  alum ; 
Florence  lake,  prepared,  in  the  same  pro- 
cess, from  the  sediment  of  cochineal,  by 
precipitation  with  solution  of  tin;  and 
madder  lake,  prepared  from  Dutch  crop 
madder,  by  precipitation  with  alum. 

LAKE  (in  Geography).  An  inland 
body  of  water  not  connected  with  the 
ocean  or  any  of  its  branches.  It  is  formed 
by  accumulation  of  water  in  a  basin,  or 
depression  of  the  surface,  deeper  than 
the  general  slope  of  the  water-line  of 
valleys.  There  are  four  distinct  kinds  of 
lakes : — 

1.  Those  which  have  no  outlet,  and 
which  do  not  receive  any  running  water. 
They  are  usually  very  small ;  some  ap- 
pear to  be  the  craters  of  extinct  volcanoes 
filled  with  water. 

2.  Those  which  have  an  outlet,  but 
which  receive  no  running  water.  They 
have  been  formed  by  springs  flowing 
into  some  large  hollow ;  the  outlets  are,  in 
some  cases,  the  beginnings  of  very  large 
rivers.  These  lakes  are  usually  in  ele- 
vated situations. 

3.  Those  which  both  receive  and  dis- 
charge streams  of  water,  as  the  immense 
bodies  of  water  in  North  America,  be- 
tween Canada  and  the  United  States,  the 


LAM 


LAN 


outlet  of  which  is  the  great  river  St. 
Laurence ;  lake  Baikal,  in  Asiatic  Russia, 
which  sends  forth  a  large  stream,  which 
joins  the  Yenesei. 

4.  Those  which  receive  streams  of 
water,  and  often  great  rivers,  but  have 
no  visible  outlet  whatever,  as  the  Caspian 
Sea  and  lake  Aral,  both  in  the  west  of 
Asia.  These  are  both  salt  lakes,  and 
were,  perhaps,  formerly  connected  with 
the  Black  Sea. 

LA'MANTINE.  The  sea-cow;  a  living 
species  of  the  herbivorous  Cetacea,  or 
Whale  tribe,  which  inhabits  the  mouths 
of  rivers  on  the  coasts  of  Africa  and 
South  America. 

LAME'LLA  (dim.  of  lamina,  a  plate). 
The  lamellae  of  the  agaric  are  those  pa- 
rallel plates,  or  gills,  in  which  the  spo- 
rules  lie ;  collectively,  they  constitute 
the  hymenium.  But  the  term  lamellar  is 
applied  to  any  part  which  is  surmounted 
by  little  plates,  or  lamellae,  as  the  style 
of  many  plants. 

LA'MELLATED  {lamella,  a  little 
plate).  A  term  applied  to  shells  whose 
substance  is  composed  of  lamellae,  or 
very  thin  plates,  which  do  not  present  a 
solid  surface,  as  in  the  pearl-oyster. 

LAME'LLIBRANCHIA'TA  {lamella, 
a  little  plate,  branchiae,  gills).  A  class  of 
bivalve  conchiferous  mollusca,  which 
respire  by  gills  in  the  form  of  vascular 
plates  of  membrane  attached  to  the 
mantle.  The  common  oyster  and  mussel 
are  examples  of  this  best  known  class  of 
acephalous  mollusca. 

LAMELLICO'RNES  {lamella,  a  little 
plate,  cornu,  a  horn).  A  family  of  the 
pentamerous  Coleoptera,  characterized  by 
the  peculiar  conformation  of  the  an- 
tennae, which  terminate  in  a  lamellated 
mass.  They  include  the  scarabaei,  and 
the  lucani  or  stag-beetles. 

LAMELLI'FEROUS  {lamella,  a  little 
plate,  fero,  to  bear).  Having  a  structure 
consisting  of  thin  plates  or  leaves,  like 
paper. 

LAME'LLIFORM  {lamella,  a  little 
plate,  forma,  shape).  Shaped  like  a  thin 
plate  or  leaf. 

LAME'LLIROSTRES  {lamella,  a  little 
plate,  rostrum,  a  beak).  The  name  given 
by  Cuvier  to  the  great  family  of  the  Ana- 
tidce,  comprising  the  duck,  the  goose,  the 
swan,  &c. 

LA'MINA.  The  Latin  term  for  a 
plate,  as  of  metal.  In  Geology,  the  word 
laminae  denotes  the  smaller  layers  of 
which  a  stratum  is  composed. 

LA'MINARITES.    The  name   given 
191 


by  Brongniart  to  a  species  of  fossil  fucus, 
found  in  the  secondary  strata  of  Aix, 
near  La  Rochelle. 

LAMP-BLACK.  A  species  of  char- 
coal, produced  by  collecting  the  smoke 
from  a  lamp ;  but  it  is  generally  obtained 
by  burning  resinous  substances,  as  the 
dregs  of  pitch,  or  pieces  of  fir-wood,  in 
furnaces,  and  collecting  the  smoke  in  a 
close-boarded  chamber. 

LAMPIC  ACID.  An  acid  obtained 
by  Sir  H.  Davy  from  the  combustion  of 
ether.  It  is  merely  acetic  acid,  com- 
bined with  some  etherous  matter. 

LAMPY'RIDjE  {\<in7ro,  to  shine).  A 
family  of  Coleopterous  insects,  of  the 
section  Malacodermi,  named  from  the 
genus  lampyris,  to  which  belongs  the 
familiar  species  noctiluca,  or  the  glow- 
worm, remarkable  for  its  emission  of 
phosphorescent  light. 

LANA  PHILOSOPHICA.  Philoso- 
phical wool,  flowers  of  zinc,  or  the  snowy 
flakes  of  white  oxide  of  zinc,  which  arise 
and  float  in  the  air  from  the  combustion 
of  that  metal. 

LAN'CEOLATE  {lancea,  a  lance). 
Lance-shaped ;  narrowly  elliptical,  taper- 
ing to  each  end,  as  the  leaves  of  many 
plants. 

LA'NDSLIP.  A  portion  of  land  which 
has  slipped  away,  owing  to  the  disturb- 
ance of  an  earthquake,  or  from  being 
undermined  by  the  washing  away  of  its 
lower  beds  by  water. 

LANE'S  CH  ARGING- JAR,  or  Spark- 
measurer.  An  apparatus  for  ascertaining 
the  intensity  of  an  electrical  charge,  by 
measuring*  the  length  of  the  spark,  and 
thus  at  the  same  time  determining  the 
power  of  a  machine  ;  and  also  for  obtain- 
ing a  number  of  successive  charges  of 
equal  intensity. 

LA'NIADiE  {lanins,  the  shrike).  The 
Shrikes;  a  family  of  the  Insessores,  or 
Perching  birds,  or  the  Excurtrices  of 
Macgillivray,  in  which  the  bill  is  ab- 
ruptly hooked  at  the  end,  and  the  notch 
is  sometimes  so  deep  as  to  form  a  promi- 
nent tooth  on  each  side.  See  Denti- 
rostres. 

LANIA'RIFORM  {lanio,  to  cut  or 
tear,  forma,  shape).  Shaped  like  the 
canine  teeth  of  the  Carnivora,  which  are 
called  laniaries  from  their  office. 

LANTA'NUM  (SavBuvu,  to  be  con- 
cealed). A  newly-discovered  metal,  so 
named  from  its  properties  being  con- 
cealed by  those  of  cerium,  with  which  it 
is  found  united.  It  occurs  in  the  cerite 
of  Bastnas. 


L  AT 


LAY 


LAPIDIFICA'TION  {lapis,  a  stone, 
fio,  to  become).  The  process  of  conver- 
sion into  stone. 

LAPI'LLI  {lapillus,  dim.  of  lapis,  a 
stone).  Small  stones ;  small  volcanic 
cinders. 

LAPIS.  A  generic  term,  signifying 
all  kinds  of  stone:  thus,  lapis  calcareus 
is  limestone ;  lapis  infernalis  is  an  old 
term  for  caustic  potash ;  lapis  calami- 
naris  is  the  impure  carbonate  of  zinc ; 
lapis  comensis  is  potstone,  an  intimate 
mixture  of  talc  and  asbest ;  lapis  lazuli 
is  a  zinc-stone,  from  which  ultra-marine 
is  prepared,  &c. 

LA'RBOARD.     By  a  person  standing 

at    the   stern   of    a   ship,    and    looking 

towards  the  prow,  the  left-hand  side  is 

termed  the  larboard,  and  the  right-hand 

>  ^"side  the  starboard. 

&JfY%  *     LA'RIDiE  {larus,  the  sea-gull).    The 

w      _^^*    Gx\)\  tribe ;  a  family  of  the  Natatores,  or 

^^^  Swimming  birds,  including  the  gull,  the 

petrel,  the  albatross,  &c,  in  which  the 

powers  of  flight  are  considerable,  while 

those    of    swimming    and    diving    are 

defective. 

LA'RVA  (Lat.,  a  mask).  A  caterpil- 
lar ;  the  earliest  state  of  insect  existence, 
so  named  by  Linnaeus  because  in  this 
condition  the  perfect  form  of  the  insect 
is  concealed,  as  it  were,  under  a  mask. 
The  term  larva  is  applied  to  the  grub, 
the  caterpillar,  and  the  maggot.  See 
Pupa. 

LARVI'PAROUS  {larva,  and  pario, 
to  produce).  A  designation  of  those  in- 
sects which  produce  their  young  in  the 
condition  of  larvae. 

LA'SIONITE.  A  phosphate  of  alumina 
from  Amberg  in  Bavaria.  It  is  a  variety 
of  hydrargyllite. 

LATE'BRICOLuE  {latebra,  a  hiding- 
place,  colo,  to  inhabit).  A  family  of 
Spiders,  which  hide  themselves  in  bur- 
rows and  fissures,  which  they  line  with 
a  web. 

LATENT  HEAT.  That  quantity  of 
heat  which  is  absorbed  during  the  con- 
version of  a  solid  into  a  liquid,  or  of  a 
liquid  into  a  vapour,  without  raising  the 
temperature  in  the  least  degree.  See 
Caloric. 

LA'TERAL  {latus,  lateris,  the  side). 
Belonging  to  the  sides  of  a  body.  Thus, 
the  lateral  teeth  of  bivalves,  where  they 
exist,  are  on  one  or  both  sides  of  the 
cardinal  teeth,  which  are  always  central. 

LATERI'GRADA  {latus,  lateris,  the 
side,  gradior,  to  advance).     A  family  of 
Spiders,  which  make  no  web,  but  run, 
192 


crab-like,  sideways  or  backwards,  and 
occasionally  throw  out  adhesive  threads 
to  entrap  their  prey. 

LATEX  {lateo,  to  be  hidden).  Any 
kind  of  liquor  squeezed  out.  This  term 
denotes,  in  Botany,  a  highly  elaborated 
and  highly  organized  juice,  which  is  not 
formed  immediately  from  the  fluid  matter 
absorbed  from  without.  The  tissue,  in 
which  this  juice  is  found,  is  termed  lati- 
ciferous  tissue,  and  more  recently  cinen- 
chyma. 

LATITUDE  {latitudo,  breadth).  The 
latitude  of  a  place  on  the  earth's  surface 
is  its  angular  distance  from  the  equator, 
measured  on  its  own  terrestrial  meri- 
dian ;  it  is  reckoned  in  degrees,  minutes, 
and  seconds,  from  0  up  to  90°,  and  north- 
wards 05  southwards  according  to  the 
•hemisphere  in  which  the  place  lies.  Thus 
the  observatory  at  Greenwich  is  situated 
in  51°  28'  40"  north  latitude. 

1.  Latitude,  parallels  of .  Small  circles 
on  the  earth's  surface  parallel  to  the 
equator.  Every  point  in  such  a  circle 
has  the  same  latitude.  Thus,  Greenwich 
is  said  to  be  situated  in  the  parallel  of 
51°  28' 40". 

2.  Latitude  of  a  star.  The  distance  of 
a  star  from  the  ecliptic,  measured  on  the 
great  circle  passing  through  the  star  and 
the  pole  of  the  ecliptic. 

LA'TROBITE.  A  pink-coloured  mine- 
ral, allied  to  felspar,  found  in  Amitok 
island,  near  the  coast  of  Labrador,  and 
named  from  Mr.  Latrobe. 

LAUMONTITE.  Lomonite.  A  zeo- 
litic  substance,  named  from  Gillet-Lau- 
mont.  It  is  also  called  efflorescent  zeo- 
lite, because  some  of  its  varieties  are  sub- 
ject to  decomposition  on  exposure  to  the 
air. 

LAURACEjE.  The  Cinnamon  tribe 
of  Dicotyledonous  plants.  Leaves  entire, 
alternate  ;  flowers  apetalous  ;  stamens 
perigyn'ous ;  fruit  baccate  or  drupaceous ; 
seeds  without  albumen. 

LAURINE.  An  acrid  and  bitter  prin- 
ciple contained  in  the  berry  of  the  laurel. 

LA'VA.  A  general  term  for  the  sub- 
stances emitted  from  volcanoes,  in  a 
fused  or  fluid  state.  In  its  ordinary  con- 
dition, it  differs  from  basalt  chiefly  in 
being  porous.  It  admits,  however,  of 
several  varieties,  which  are  sufficiently 
characterized  by  the  terms  compact,  vesi- 
cular, slaggy,  and  spumous. 

LAYERING.  The  process  of  propa- 
gating young  plants  from  a  parent  stock, 
by  laying  down  a  branch,  and  then  sepa- 
rating it  from  its  parent.    See  Malleolus. 


LEA 


LEG 


LA'ZULITE.  Lapis  lazuli.  A  blue 
mineral  from  Styria  and  the  Tyrol,  which 
furnishes  the  valuable  pigment  known 
by  the  name  of  ultra-marine.  It  is  a 
silicate  of  alumina,  soda,  and  lime,  and  is 
sometimes  confounded  with  klaprothite, 
or  blue  spar,  which  is  a  phosphate  of 
alumina. 

LEAD.  A  white  metal  with  a  blue 
tinge;  the  softest  of  all  the  durable 
metals.  White  lead,  or  ceruse,  is  a  white 
substance  produced,  in  the  form  of 
flakes,  by  the  action  of  the  vapour  of 
vinegar  on  lead.  It  may  be  dissolved  in 
acetic  acid,  forming  a  crystallizable  salt, 
called  sugar  of  lead,  from  its  sweet  taste. 
Red  lead,  or  minium,  is  the  red  oxide  of 
lead,  a  tasteless  powder  of  an  intensely 
red  colour.  Black  lead,  or  graphite,  is  a 
misnomer,  being  a  carburet  of  iron. 

LEAF  OF  PLANTS.  The  leaf  is  an 
expansion  of  the  bark  at  the  base  of  a 
leaf-bud,  prior  to  which  it  is  developed. 
It  consists  of  a  midrib,  on  each  side  of 
which  is  a  parenchymatous  expansion, 
composed  of  a  double  stratum  of  cellular 
tissue,  separated  by  vessels.  A  simple 
leaf  is  that  of  which  the  lamina  or  blade 
consists  of  one  piece  only,  whatever  may 
be  the  depth  of  its  divisions  ;  a  compound 
leaf  is  that  of  which  the  cellular  tissue  is 
separated  into  several  portions,  each 
forming  a  complete  blade  by  itself. 

LEAF-STALK.  Petiole.  That  part 
of  the  leaf  which  connects  the  blade  with 
the  stem.  It  consists  of  one  or  more 
bundles  of  fibro-vascular  tissue  sur- 
rounded by  cellular  substance. 

LEAFLET.  The  designation  of  each 
of  those  small  separate  leaves,  which 
together  compose  a  compound  leaf. 

LEAGUE.  The  twentieth  part  of  a 
degree  of  latitude,  or  three  geographical 
miles,  each  of  which  is  the  sixtieth  part 
of  a  degree.  The  French  have  two  kinds 
of  league;  the  first  consisting  of  2000 
toises,  or  2-42  English  statute  miles ;  the 
second  of  2-77  English  miles,  or  25 
leagues  to  the  degree ;  the  former  is  their 
legal  posting  measure. 

League,  Nautical.  Seamen  measure 
by  nautical  miles,  60  of  which  make  a 
degree  of  latitude,  or  a  degree  of  longi- 
tude at  the  equator ;  and  three  nautical 
miles  make  a  nautical  league,  which  is, 
accordingly,  3*45  land  or  statute  miles, 
or  three  miles,  four  tenths,  five  hun- 
dredths, which  is  easily  remembered. 

LEAP-YEAR.  The  name  given  to 
every  fourth  year  of  the  Julian  calendar, 
in  which  one  additional  day— the  29th  of 
193 


February— is  reckoned.  The  year  is  so 
called,  because  the  day  of  the  month, 
after  February,  leaps  over  a  day  of  the 
week.  The  reason  for  adding  a  day 
every  fourth  year  is,  because  the  tropical 
exceeds  the  civil  year  by  six  hours,  which 
excess  amounts,  in  four  years,  to  one 
day.    See  Bissextile. 

LEAST  SQUARES,  METHOD  OF. 
A  method  of  finding  the  most  probable 
truth,  when  a  number  of  discordant  ob- 
servations have  been  made  upon  a  phe- 
nomenon. "If  three  observations  give 
93, 94,  and  98,  then  the  mean  of  the  three 
is  95,  and  if  this  be  assumed  as  true,  it 
is  also  assumed  that  the  errors  of  the 
observations  were  2,  1,  and  3.  The  sum 
of  the  squares  of  these  is  4+1  +  9,  or  14, 
and  this  is  the  least  possible  sum  which 
can  be  thus  obtained.  If,  for  example, 
we  assume  any  thing  but  95,  say  95*  1,  the 
assumed  errors  are  then  2*1,  l'l,  and 
2*9,  the  squares  of  which  are  4*41,  T21, 
and  841,  the  sum  of  which  is  1403,  more 
than  14."— Pen.  Cycl. 

LEAVEN  or  YEAST.  A  substance 
which  possesses  the  power  of  commenc- 
ing fermentation  in  other  substances. 

LECO'NORIN.  A  white  crystalline 
substance  procured  from  the  Leconora 
tartarea  and  other  lichens,  employed  in 
the  manufacture  of  cudbear. 

LEE.  An  epithet  to  distinguish  that 
half  of  the  horizon  to  which  the  wind  is 
directed,  from  the  other  part  where  it 
arises,  which  latter  is  accordingly  called 
to  windward. 

LEE'LITE.  A  red  siliceous  stone 
found  at  Gryphytta  in  Westmannia,  and 
named  from  Mr.  Lee  of  Cambridge. 

LEEWARD.  The  lee-side  of  a  ship  is  L/^C^J, 
that  half  of  a  ship  (divided  lengthways), 
which  is  opposite  to  that  on  which  the 
wind  blows  when  it  crosses  her  course, 
and  which  is  called  the  weather-side.  All 
objects  on  the  lee-side  are  said  to  be  to 
the  leeward,  and  those  on  the  weather- 
side  to  the  windward  of  the  vessel. 

LEEWAY.  The  angle  made  by  the  line 
on  which  the  ship  should  run,  according 
to  the  point  of  the  compass  steered  upon, 
and  the  real  line  of  the  ship's  way  occa- 
sioned by  contrary  winds,  rough  sea,  or 
the  set  of  a  current. 

LEGER  LINES  and  SPACES.  In 
Music,  the  lines  and  spaces  which  are 
added  to  the  staff,  when  the  notes  ex- 
ceed the  ordinary  compass. 

LEGU'MEN  (lego,  to  gather).  A  le- 
gume ;  a  one-celled,  two-valved,  superior 
fruit,  dehiscent  by  a  suture  along  its  face 


LEM 


LEN 


and  its  back,  and  bearing  seeds  on  each 
margin  of  its  ventral  suture. 

1.  Legumen  Lomentaceum.  A  lomen- 
tum  ;  a  fruit  differing  from  a  legume  in 
being  contracted  in  the  spaces  between 
each  seed,  and  there  separating  into  dis- 
tinct pieces. 

2.  Legumin.  A  peculiar  principle, 
found  in  the  fleshy  cotyledons  of  the 
seeds  of  papilionaceous  plants. 

LEGUMINO'S^E  {legumen,  a  legume). 
The  Pea  tribe  of  Dicotyledonous  plants. 
Herbs  with  leaves  alternate ;  stamens  peri- 
gynous,  monadelphous,  or  diadelphous; 
ovarium  superior,  solitary,  simple ;  fruit 
leguminous ;  seeds  without  albumen. 

LEIDENFROST'S  PHENOMENON. 
If  water  in  minute  quantities  be  placed 
on  a  red-hot  plate,  it  will  not  boil,  nor 
evaporate  quickly,  but,  as  the  metal  be- 
gins to  cool,  the  liquid  assumes  a  globular 
figure,  and  exhibits  a  rotatory  and  oscil- 
lating movement,  during  the  continuance 
of  which  the  process  of  evaporation  is 
carried  on  much  less  rapidly  than  during 
ebullition.  When  the  metal  has  cooled 
down  to  a  still  lower  degree,  the  liquid 
boils  with  great  violence,  and  is  dispersed 
in  every  direction. 

LEIOTRICHA'N^E.  Silky  chatterers ; 
a  sub-family  of  birds,  in  the  system  of 
Mr.  Swainson,  belonging  to  the  Ampelidce, 
or  Chatterers,  and  named  from  the  genus 
Leiothrix. 

LEMMA  {\r\nna,  any  thing  taken  or 
received).  A  proposition  introduced 
merely  for  the  purpose  of  establishing 
some  more  important  proposition.  Thus, 
in  a  treatise  on  mechanics,  if  it  were 
necessary  to  prove  certain  propositions 
of  geometry,  those  propositions  would  be 
lemmas.  In  Logic,  a  lemma  is  an  as- 
sumption or  premiss  taken  for  granted. 

LEMNIAN  EARTH.  A  compound  of 
aluminum,  found  in  the  island  of  Lemnos. 
It  is  also  called  sphragide  (cr^payir,  a  seal), 
and  terra  sigillata,  from  its  being  cut 
into  pieces,  and  stamped  with  a  seal.  It 
is  similar  to  Armenian  bole. 

LEMNI'SCATA  {XnpviaKot,  a  rib- 
and). In  Geometry,  a  curve  of  the 
fourth  degree,  having  the  form  of  the 
figure  8,  and  of  which  the  equation  is 
x*  +  y2=  a\/x2—y*.  It  is  the  locus  of 
the  point  in  which  a  tangent  to  an  equi- 
lateral hyperbola  meets  the  perpendicu- 
lar on  it  drawn  from  the  centre.  There 
are  many  other  curves  of  the  same  order 
with  a  similar  form,  but  their  equations 
differ  from  the  above. 

LEMNI'SCUS.  The  Latin  term  for 
194 


riband ;  and,  hence,  applied  to  the  minute 
riband-shaped  appendages  of  the  genera- 
tive pores  in  Entozoa. 

LEMU'RIDjE.  A  family  of  quadru- 
manous  animals,  named  lemurs  which 
supply  the  place  of  monkeys  in  Mada- 
gascar and  some  parts  of  Africa  and 
India. 

LENGTH  OF  SHELLS.  Spiral  shells 
are  measured  from  the  tip  of  the  spire  to 
the  base,  and  therefore  perpendicularly. 
The  length  of  bivalves  is  taken  horizon- 
tally; thus,  the  solens  is  the  longest 
shell  of  this  tribe,  the  length  being  taken 
from  the  anterior  to  the  posterior  margin. 

LENS  (lens,  a  bean).  Properly,  a  small 
roundish  glass,  shaped  like  a  lentil,  or 
bean.  In  physics,  the  term  is  applied  to 
any  transparent  medium,  the  essential 
character  of  which  is,  that  it  shall  refract 
the  rays  of  light,  so  that  the  divergence, 
or  convergence,  of  those  rays  shall  be 
equally  produced  after  their  passage 
through  the  lens. 

1.  The  usual  forms  and  names  of  lenses 
are  the  convex,  which  converges  the  rays ; 
the  concave,  which  disperses  them ;  the 
plano-convex,  having  one  surface  plane, 
and  the  other  convex ;  the  double  convex, 
having  both  sides  convex ;  the  plano- 
concave, having  one  surface  plane,  and 
the  other  concave;  the  double  concave, 
having  two  concave  surfaces ;  and  the 
meniscus,  having  one  side  concave,  and 
the  other  convex. 

2.  The  point  where  no  refraction  is 
produced  on  perpendicular  rays,  is  called 
the  axis  of  the  lens,  which  is  a  right  line 
passing  through  its  centre,  and  perpendi- 
cular to  both  its  surfaces.  In  every  beam 
of  light,  the  middle  ray  is  called  its 
axis.  Rays  of  light  are  said  to  fall  di- 
rectly upon  a  lens,  when  their  axes  coin- 
cide with  the  axis  of  the  lens ;  otherwise 
they  are  said  to  fall  obliquely.  The  point 
at  which  the  rays  of  the  sun  are  collected, 
by  passing  through  a  lens,  is  called  the 
principal  focus  of  that  lens. 

3.  Lens,  Coddington.  A  well-known 
lens,  consisting  of  a  sphere  of  glass 
divided  into  two  portions  by  a  deeply  cut 
circular  groove,  which  is  filled  up  with 
opaque  matter.  The  lens  of  the  cuttle- 
fish is  a  precisely  similar  instrument. 

LENTICE'LL^ffi.  Lenticular  glands, 
or  brown  oval  spots  found  upon  the  bark 
of  many  plants,  especially  willows.  They 
are  considered  by  De  Candolle  to  bear  the 
same  relation  to  roots  as  buds  bear  to 
young  branches. 

LENTI'CULAR    (lenticula,    a    little 


LEP 


LEU 


lens).  Lens-shaped ;  small,  depressed, 
and  doubly-convex,  as  the  seed  of  ama- 
ranth. 

LENTIL-ORE.  An  arseniate  of  cop- 
per, also  called  the  lenticular  arseniate. 

LE'NZINITE.  A  silicate  of  alumina, 
found  at  Eifeld  in  Prussia,  and  distin- 
guished into  the  opaline  and  the  argilla- 
ceous varieties. 

LEO  WITH  COMA  BERENICES. 
The  fifth  of  the  zodiacal  constellations, 
containing  95  stars,  of  which  Regulus  is 
the  principal.  It  indicates  the  second 
month  of  winter,  and  extends  from  the 
20th  of  January  to  the  20th  of  February. 
In  Egypt  the  earth  assumes  its  most 
beautiful  aspect  in  the  month  of  Fe- 
bruary; a  part  of  the  harvest  is  already 
begun.  The  king  of  animals  was  chosen 
to  typify  the  strength  and  the  magni- 
ficence of  nature  at  this  period. 

LEO  MINOR.  A  modern  northern 
constellation,  containing  fifty-three  stars. 
LE'PADITES.  A  designation  of  the 
reputed  bivalvular  opercula  of  am- 
monites, found  at  Solenhofen,  and  also 
termed  trigonellites,  solenites,  and  apty- 
chus. 

LE'PADOIDS.  A  group  of  Cirrho- 
pods,  named  from  the  typical  genus 
lepas,  and  commonly  known  by  the  name 
of  barnacles.  They  are  distinguished  by 
their  pedunculated  character  from  the 
other  group,  or  balanoids,  which  are 
sessile. 

LEPIDODE'NDRON  {Xenk,  Xeirtdot, 
a  scale,  devdpdv,  a  tree).  A  genus  of 
fossil  plants  of  the  coal  measures,  inter- 
mediate in  character  between  the  Lyco- 
podiums  and  coniferous  plants;  they  ap- 
pear, from  their  great  abundance,  to  have 
contributed  in  large  proportion  to  the 
solid  matter  of  coal.  The  name  is  de- 
rived from  the  trunk  of  the  tree  being 
marked  along  its  whole  length  with 
scales  or  scars. 

LE'PIDOLITE  (XeffJc,  a  scale,  A/0o?, 
a  stone).  A  name  for  several  beautiful, 
variously-coloured,  scaly  varieties  of 
lithia-mica,  some  of  which  are,  however, 
referable  to  the  silicates  combined  with 
fluorides.  They  are  found  at  Rozna  in 
Moravia,  and  other  places. 

LEPIDO'PTERA  {Xewlt,  Xeiridos,  a 
scale,  7TT€p6v,  a  wing).  An  order  of  in- 
sects which  have  four  membranous  and 
scaly  wings,  and  undergo  complete  meta- 
morphosis, as  the  butterfly,  the  moth,  &c. 
All  the  Caterpillars  are  the  larvae  of  lepi- 
dopterous  insects. 
LE'PIDOTE  (AeTTi?,  a  scale).  Le- 
195 


prous  ;     covered   with   minute    peltate 
scales,  as  the  leaf  of  elaeagnus. 

LEPI'SMAD,E.  A  family  of  wingless 
insects,  belonging  to  the  order  Thysa- 
noura,  in  which  the  abdomen  is  termi- 
nated by  long  jointed  bristles,  as  in  the 
sugar-louse. 

LE'PORIDjE  (lepus,  a  hare).  The 
Hare  tribe;  a  family  of  the  Rodentia, 
distinguished  from  all  the  other  families 
by  the  presence  of  two  small  incisors  be- 
hind the  rodent  teeth.  The  hare  is  a 
ruminating  animal,  though  destitute  of 
the  complex  stomach  of  the  ruminantia. 
LE'PTIDES.  A  sub-family  of  dipte- 
rous insects,  of  the  family  Brachystoma, 
named  from  the  genus  leptis. 

LEPTOPHPNA.  A  sub-family  of  ser- 
pents, belonging  to  the  family  Colubridae, 
and  comprising  the  genera  leptophis  and 
dryinus. 

LEPUS.  The  Hare,  a  southern  con- 
stellation, containing  nineteen  stars. 

LERNjEIFO'RMES.  An  order  of  the 
edentulous  crustaceans,  in  which  the 
extremities  are  but  little  developed,  and 
the  body  presents  great  variety  of  form. 

LETTERS  FOR  STARS.  Towards 
the  end  of  the  sixteenth  century,  Bayer 
published  the  first  charts  in  which  the 
stars  were  not  only  constellated,  but  dis- 
tinguished in  their  constellations  by 
letters.  Beginning  with  the  Greek  alpha- 
bet, he  put  a  to  the  star  which  he  con- 
sidered brightest,  /3  to  that  which  was 
next  in  brightness,  and  so  on  throughout 
the  constellation,  using  the  Roman  letters 
when  the  Greek  were  exhausted.  His 
successors  added  more  letters,  frequently 
going  through  both  the  Greek  alphabet 
and  the  Roman,  where  Bayer  had  ex- 
hausted only  a  part  of  the  Greek,  and 
sometimes  even  adding  another  alphabet 
of  capital  Roman  letters. 

LEUCIN  (Aev*co9,  white).  A  peculiar 
white  principle  obtained  from  muscle. 
Nitric  acid  converts  it  into  a  crystalliz- 
able  acid,  called  nitro-leucic. 

LEU'CITE  (Aei/Kop,  white).  Amphi- 
gen.  A  mineral  allied  to  felspar,  found 
chiefly  at  Vesuvius,  in  separate  crystals 
of  various  sizes  and  degrees  of  trans- 
parency, massive,  embedded  in  pyroxenic 
and  other  lavas. 

LEUCOL.  A  particular  substance 
produced  in  the  distillation  of  coal. 

LEU'TTRITE.  A  greyish-white  mine- 
ral found  at  Leuttra,  near  Jena  in  Sax- 
ony. It  appears  to  be  a  recomposed 
rock,  analogous  to  some  of  the  sandy 
varieties  of  domite. 

K2 


LEV 


LIB 


LEVEL.  Two  points  on  the  surface 
of  the  earth  are  said  to  be  on  the  same 
level,  where  they  are  equally  distant  from 
the  earth's  centre.  A  level  surface,  there- 
fore, is  not  a  plane,  but  a  portion  of  a 
spherical  surface;  and  this  is  the  form 
which  a  sheet  of  water,  or  any  other 
liquid,  naturally  assumes. 

Horizontal  and  dead  level.  There  are 
various  instruments  used  in  levelling, 
which  are  called  levels.  These  all  give  a 
horizontal  level,  that  is,  a  tangent  to  the 
earth's  surface ;  and  in  the  case  of  a 
drain  or  canal,  the  bottom  of  the  exca- 
vation must  be  carried  lower  than  the 
level  indicates,  otherwise  the  water  would 
not  run.  The  declivity  must  be  in  a 
circle  equivalent  to  that  of  the  earth's 
circumference  before  the  water  could 
reach  it,  and  this  would  then  be  termed 
a  dead  level. 

LE'VER  (levo,  to  raise).  A  physical 
or  compound  lever  is  any  inflexible  rod  or 
solid  body  whatever,  supported  on  one 
point,  and  acted  on  at  two  other  points, 
by  two  forces  tending  to  move  it  in  oppo- 
site directions  about  the  point  of  support. 
The  two  forces  acting  on  the  lever  are 
called  the  power  and  the  weight,  and  the 
point  on  which  the  lever  is  supported,  or 
about  which  it  turns,  is  called  the  ful- 
crum. The  power  of  this  instrument 
depends  on  the  proportion  between  the 
lengths  of  the  parts  of  the  lever  on  each 
side  of  the  fulcrum. 

1.  Lever,  one,  or  two-armed.  1.  In  the 
one-armed  lever,  the  power  and  the 
weight  are  both  on  one  side  of  the  ful- 
crum, as  in  the  common  wheel-barrow. 
2.  Tn  the  two-armed  lever,  the  fulcrum 
is  between  the  power  and  the  weight, 
being  either  equidistant  from  the  two 
forces,  or  nearer  to  one  of  the  forces  than 
to  the  other. 

2.  Levers  are  rectilinear  or  curvilinear, 
according  as  their  arms  are  straight  or 
curved  lines.  A  lever  is  angular,  when 
the  arms  form  an  angle,  in  which  case 
the  fulcrum  is  at  the  vertex  of  the 
angle. 

3.  Lever,  Universal.  An  instrument 
constructed  by  combining  the  lever  with 
the  wheel  and  axle;  its  object  is  to  give 
a  continued  rectilinear  motion  to  a  heavy 
body,  by  means  of  the  reciprocating 
motion  of  the  lever. 

LEVIGATION  (Icevigo,  to  polish  ; 
from  Icevis,  smooth).  The  process  of 
rubbing  earths  and  some  metallic  sub- 
stances with  a  muller  upon  a  flat  table 
of  hard  stone.  Some  fluid  is  added  to 
196 


assist  the  operation,  and  in  this  respect 
it  differs  from  trituration. 

LE'VINE.  A  scarce  zeolitic  sub- 
stance, occurring  in  the  cavities  of  an 
amygdaloid  rock,  at  Dalsnypen  in  Faroe. 

LEY.  Lixivium.  A  technical  term 
for  a  solution  of  alkali  in  water. 

LEYDEN  JAR.  An  apparatus  for 
accumulating  and  condensing  electricity, 
constructed  on  the  principle  that  the  oppo- 
site electricities  may  be  held  in  a  latent 
state.  It  consists  of  a  cylindrical  glass- 
jar  coated  to  a  certain  height,  inside  and 
outside,  with  tinfoil,  so  that  every  point 
of  both  sides  of  the  glass  may  be  brought 
into  communication  at  the  same  moment. 
To  convey  the  fluid  to  the  interior  of  the 
jar,  a  brass  wire  runs  through  its  lid,  the 
upper  end  terminating  in  a  ball,  and  the 
lower  end,  divided  into  several  fine  points, 
touches  the  foil  within  the  jar.  A  com- 
bination of  such  jars  is  called  an  electri- 
cal battery. 

LHF/RZOLITE.  A  mineral  consist- 
ing of  coccolite  mixed  with  serpentine. 

LIAS.  A  subdivision  of  the  Oolitic  or 
Jurassic  system  of  Geology,  consisting  of 
a  great  argillaceous  deposit  with  some 
thick  arenaceous  bands,  and  many  con- 
cretions and  beds  of  argillaceous  lime- 
stone. It  is  continued  without  interrup- 
tion from  the  coast  of  Dorsetshire  to  the 
north-east  coast  of  Yorkshire.  The  term 
lias  is  supposed  to  be  derived  from  the 
appearance  of  the  bed  in  riband-like 
layers  of  different  colours,  observed  in 
some  parts  of  England. 

LIBELLU'LIDiE  {libellula,  the  dra- 
gon-fly). A  group  of  neuropterous  in- 
sects, which  are  aquatic  in  their  prepa- 
ratory states,  and  emerge  from  the  water 
at  the  period  of  their  final  metamor- 
phosis. 

LIBER.  The  inner  bark  of  a  tree, 
used  instead  of  paper  by  the  ancients  to 
write  upon.  In  botanical  language,  it 
denotes  the  interior  fibrous  portion  of  the 
bark,  lying  immediately  upon  the  albur- 
num ;  the  endophloeum  of  later  writers. 
See  Bark. 

LIBRA.  The  Balance;  the  seventh 
of  the  zodiacal  constellations,  consisting 
of  fifty-one  stars,  the  principal  of  which 
is  Zubenich  Meli.  It  denotes  the  first 
month  of  spring,  and  extends  from  the 
20th  of  March  to  the  20th  of  April.  This 
month  answers  to  the  vernal  equinox 
and  the  equality,  or  balance,  of  the  days 
and  nights. 

LIBRA'TION  {libro,  to  balance).  A 
slight  swaying   motion,   like  that  of  a 


LIE 


LIG 


balance.  The  expression  is  applied  by 
astronomers  to  an  apparent  oscillation  of 
the  moon,  in  consequence  of  which  she 
exhibits  sometimes  a  little  more,  some- 
times a  little  less,  of  one  side  or  the 
other. 

1.  Libration  in  Longitude.  The  phe- 
nomenon by  which  the  moon,  during  the 
period  of  acceleration,  exhibits  on  the 
east  some  portion  of  her  surface  not 
previously  seen,  whilst  corresponding 
parts  disappear  on  the  west.  The  converse 
of  this  takes  place  during  retardation. 

2.  Libration  in  Latitude.  The  pheno- 
menon by  which  the  moon,  in  conse- 
quence of  her  axis  of  rotation  being  in- 
clined to  her  orbit,  and  of  its  always 
preserving  its  parallelism,  turns  each  of 
her  poles  to  us  alternately,  and  displays 
to  us  the  spots  situated  about  it. 

3.  Diurnal  Libration.  The  phenome- 
non by  which  the  moon,  when  on  the 
horizon,  presents  some  parts  the  more 
of  one  side,  and  a  corresponding  portion 
the  less  of  the  other  side.  This  is  in 
consequence  of  the  spectator  being  re- 
moved from  the  centre  of  the  earth 
(towards  which  the  same  hemisphere  of 
the  moon  is  constantly  turned)  by  the 
length  of  the  earth's  radius. 

LICHE'NES.  The  Lichen  tribe  of  the 
Aphyllae,  or  leafless  plants.  Aerial,  leaf- 
less, perennial  plants,  spreading  over 
almost  all  dry  surfaces,  of  trees,  stones, 
&c. ;  reproductive  organs  are  sporules 
lying  in  thecae  in  the  medullary  sub- 
stance, or  separated  cellules  of  the  me- 
dullary layer  of  the  thallus. 

LFCHENIN.  Lichen  starch  ;  a  pecu- 
liar vegetable  product,  obtained  from  the 
cetraria  islandica,  or  liverwort ;  it  is  said 
to  combine,  like  the  alkalies,  with  acids, 
but  it  does  not  form  crystallizable  salts 
with  them. 

LICHTENBERG'S  FIGURES.  The 
phenomena  observed  on  discharging  a 
positive  spark  and  a  negative  spark  on 
different  parts  of  the  same  polished  re- 
sinous surface  ;  the  two  electricities  will 
be  retained,  in  a  latent  state,  on  their  re- 
spective spots.  If  the  surface  be  now 
sprinkled  with  flowers  of  sulphur,  the 
powder  will  be  attracted  and  retained  by 
the  electricities;  and,  if  the  rest  of  the 
powder  be  blown  away,  a  radiant  star- 
like figure  will  be  found  at  the  positively 
electrified  spot,  and  a  round  clouded 
speck  at  the  spot  which  wa3  negatively 
electrified. 

LIE'VRITE.  A  pyroxenic  mineral, 
also  called  ilvaite  and  yenite,  occurring  in 
197 


particularly  perfect  crystals,  chiefly  from 
Elba. 

LFGAMENT  (ligo,  to  bind).  An  ex- 
ternal substance,  by  which  the  two  valves 
of  acephalous  testacea  are  united,  and 
which,  in  fact,  is  the  true  hinge.  The 
internal  part  is  generally  composed  of 
another  substance,  and  is  called  the  car- 
tilage. 

LIGHT.  The  agent  of  vision,  or  the 
cause  of  those  sensations  and  colours 
which  we  refer  to  the  eye,  or  sense  of 
seeing,  as  their  source.  It  is  distin- 
guished into  two  kinds;  viz.  natural 
light,  proceeding  from  the  sun  and  stars ; 
and  artificial  light,  proceeding  from 
bodies  which  are  strongly  heated,  and 
thus  become  incandescent. 

1.  A  ray  is  a  single  line  of  light,  as  it 
comes  from  a  luminous  body.  A  beam 
of  light  is  a  body  of  parallel  rays.  A 
pencil  of  light  is  a  body  of  diverging  or 
converging  rays.  Divergent  rays  are 
such  as  come  from  a  point,  and  con- 
tinually separate  wider  apart,  as  they 
proceed.  Convergent  rays  are  those  which 
approach  each  other,  so  as  to  meet  at  a 
common  point.  Luminous  bodies  emit 
rays,  or  pencils  of  light,  in  every  direc- 
tion, so  that  the  space  through  which 
they  are  visible  is  filled  with  them  at 
every  possible  point. 

2.  Light  barometrical.  A  luminous 
appearance  exhibited  in  the  vacuum  of 
some  barometers,  when  the  mercury  is 
shaken  in  the  dark— a  phenomenon  pro- 
bably depending  on  electricity. 

LIGHT-EQUATION.  Roemer  ob- 
served that  the  eclipses  of  the  satellites 
of  Jupiter,  which  occurred  at  and  about 
the  opposition  of  the  planet,  or  its  nearest 
point  to  the  earth,  took  place  too  soon 
for  his  calculation  ;  whereas  those  which 
happened  when  the  earth  was  in  the 
part  of  its  orbit  most  remote  from  Jupi- 
ter, were  always  too  late.  The  cor- 
rection required  in  consequence  of  the 
time  employed  by  light  in  traversing 
the  solar  system,  is  called  the  light-equa- 
tion. 

LIGHTNING.  A  phenomenon  usually 
referred  to  the  accumulation  of  sensible 
electricity  in  the  atmosphere,  and  its 
consequent  neutralization  :  a  strong  elec- 
tric spark  traverses  a  stratum  of  air 
intervening  between  oppositely  electrified 
clouds,  or  between  a  cloud  and  the  earth's 
surface.    See  Conductors  Metallic. 

LI'GNIN  (lignum,  wood).  The  basis 
of  woody  fibre— the  most  durable  product 
of  vegetation.  When  heated  in  close 
K3 


LI  M 


LI  N 


vessels,  it  yields  pyro-ligneous  acid;  and 
a  peculiar  spirituous  liquor  is  produced, 
called  pyro-xylic  spirit. 

LIGNIPE'RDOUS  {lignum,  wood, 
perdo,  to  destroy).  A  term  applied  to 
insects  which  destroy  wood. 

LI'GNITE  (lignum,  wood).  A  variety 
of  coal,  of  a  brown,  dull,  compact,  or 
laminated  appearance,  often  woody,  burn- 
ing with  flame  and  smoke. 

LI'GNONE  (lignum,  wood).  Xylite. 
A  liquid  which  exists  in  commercial 
pyroxylic  spirit, — a  product  of  the  dis- 
tillation of  wood. 

LI'GNUM.  Wood;  that  portion  of 
arborescent  plants  which  comprises  the 
alburnum  and  the  duramen. 

LI'GULA.  A  peculiar  membranous 
process  at  the  top  of  the  sheath  in  grasses, 
between  the  sheath  and  the  blade. 

LI'GULATE  FLOWERS  (ligula,  a 
strap).  Strap-shaped  flowers,  or  those 
which  have  a  gamopetalous  corolla  slit  on 
one  side,  and  opened  flat,  as  in  many  of 
the  composite  plants. 

LI'GURITE.  A  silicate  of  alumina, 
lime,  and  magnesia,  found  in  a  talcose 
rock  on  the  banks  of  the  Stura  in  the 
Apennines.  It  is  reckoned  superior  to 
the  chrysolite  as  a  gem,  in  colour,  hard- 
ness, and  transparency. 

LILIA'CEjE.  The  Lily  tribe  of  Mo- 
nocotyledonous  plants.  Bulbous,  tuber- 
ous, creeping,  or  arborescent  plants; 
calyx  and  corolla  inferior,  coloured,  regu- 
lar ;  stamens  6 ;  anthers  opening  in- 
ward ;  fruit  3-celled. 

LILY  ENCRINITE.  A  radiated  ani- 
mal occurring  in  the  seas  of  the  new  red 
sandstone,  enclosed  within  a  stony  habi- 
tation, said  to  consist  of  nearly  thirty 
thousand  separate  pieces,  and  planted 
upon  a  stony  but  moveable  column, 
nearly  cylindrical,  and  attached  at  its 
base  to  the  solid  rock.    See  Encrinites. 

LIMACI'NjE.  Slugs ;  a  sub-family  of 
the  Helicidce,  named  from  the  genus 
Umax,  and  having  either  no  shell,  or  one 
much  too  small  to  contain  the  body. 

LIMB.  A  term  applied  to  the  curved 
edge  of  a  circle,  as  the  graduated  limb  of 
a  quadrant.  In  Astronomy,  it  denotes 
the  outermost  border  of  the  sun  or  moon ; 
thus,  it  is  usual  to  speak  of  the  moon's 
lower  or  upper  limb,  and  even  of  her 
eastern  or  western  limb ;  and  especially, 
in  the  case  of  an  eclipse,  when  a  portion 
of  her  disc  is  obscured. 

LI'MBILITE.     A  compact   mineral, 
found  in  the  form  of  irregular  grains  in 
the  volcanic  hill  of  Limbourg. 
198 


LIME.  The  oxide  of  calcium ;  an  al- 
kaline earth,  found  as  a  carbonate  in 
marble,  chalk,  and  limestone.  These 
substances  become  lime,  when  burned  in 
a  white  heat.  Quick  lime  is  limestone 
which  has  been  burned,  and  acquired 
new  properties.  Slaked  lime  is  the  pow- 
der produced  by  pouring  water  upon 
quicklime  ;  this  is  a  hydrate,  and,  when 
diffused  through  water,  yields  the  sub- 
stance called  milk  or  cream  of  lime. 

LIMESTONE.  A  designation  of  the 
various  modifications  of  calcareous  rocks, 
consisting  of  carbonate  of  lime.  The 
principal  kinds  are  the  primary  or  crys- 
talline, the  secondary  or  compact,  the 
oolite,  chalk,  &c.  Saccharine  limestone 
is  a  term  applied  to  a  few  small  beds  oc- 
curring in  the  inferior  stratified  series  of 
rocks,  from  its  resemblance  to  refined 
sugar;  it  is  sometimes  called  primitive 
limestone,  from  the  period  of  its  occur- 
rence in  this  series. 

LIMIT  (limito,  to  bound).  A  bound- 
ary. But  the  term  limit  is  employed  in 
the  sciences  in  a  wider  sense.  There  are 
certain  effects  in  Natural  Philosophy,  as 
well  as  quantities  in  Mathematics,  which 
cannot  be  determined  with  accuracy; 
but,  in  many  of  these  cases,  we  may  fix 
a,  point  which  that  effect  or  quantity  must 
certainly  exceed,  and  another  at  which 
it  cannot  possibly  arrive.  These  points 
are  the  limits  of  the  problem.    Thus, 

1.  We  cannot  predict  the  exact  height 
at  which  the  mercury  will  stand,  at  the 
level  of  the  sea,  in  a  barometer,  on  any 
future  day;  but  we  may  assert,  from 
past  e-perience,  that  it  will  be  some- 
where between  twenty-eight  and  thirty- 
one  inches.     So  also, 

2.  We  cannot  determine  exactly  the 
length  of  the  circumference  of  a  circle ; 
but  we  are  certain  that  it  is  greater  than 
that  of  any  inscribed  polygon,  and  less 
than  that  of  any  circumscribed  one,  how- 
ever numerous  their  sides  may  be. 

LIMNACI'NiE.  River-snails  ;  a  sub- 
family of  the  Helicince,  named  from  the 
genus  limnea,  and  having  only  two  de- 
pressed or  flattened  tentacula,  and  no 
operculum. 

LIMNiE'ID-ffi  (Xifjivt),  a  marsh).  A 
family  of  fresh-water  testaceous  mol- 
lusca,  consisting  of  the  genera  limncea, 
physa,  and  planorbis.  Lamarck  defines 
them  as  amphibian  trachelipods,  gene- 
rally inoperculate,  with  flattened  tenta- 
cula, and  a  spirivalve  shell. 

LINA'CEjE.  The  Flax  tribe  of  dico- 
tyledonous plants.    Herbaceous   plants, 


LIN 


LIT 


with  leaves  usually  alternate ;  flowers  sym- 
metrical, polypetalous  ;  stamens  hypo- 
gynous ;  ovarium  entire,  many-celled; 
seeds  compressed  and  inverted. 

LINE.  Euclid  defines  a  mathematical 
line  as  that  which  has  "  length  without 
breadth."  This,  however,  is  a  pure  ab- 
straction, and  can  be  only  mentally  con- 
ceived by  the  aid  of  another  abstraction  : 
thus,  if  a  mathematical  point  be  imagined 
to  move  in  space,  and  to  mark  its  course 
by  a  trace  or  track,  this  trace  or  track 
will  be  a  mathematical  line.  Such  a  line 
is  the  boundary  of  a  surface,  having 
length  only.  A  right  line,  or  straight 
line,  is  that  which  lies  evenly  between 
its  extreme  points.  Any  line  of  which 
no  part  is  a  right  line,  is  called  a  curve. 

LINEAR  EQUATION.  An  equation 
of  the  first  degree;  in  other  words,  an 
equation  connected  with  straight  lines. 

LINNjE'AN  SYSTEM.  A  method  of 
classifying  plants,  introduced  by  Lin- 
naeus, and  founded  on  modifications  of 
the  sexual  apparatus.    See  Botany. 

LIPS  OF  SHELLS.  The  two  sides  of 
the  aperture  of  spiral  shells  are  termed 
the  lips.  That  which  joins,  and  gene- 
rally folds  over,  the  lower  part  of  the 
columella,  is  called  the  inner  lip,  while 
that  part  of  the  circumference  which  is 
opposite  is  the  outer.  The  latter,  of 
course,  is  found  in  all  shells,  because  it 
is  the  termination  of  the  last  whorl ;  but 
the  former  is  frequently  absent,  or  indi- 
cated merely  by  a  thin,  whitish,  almost 
transparent  enamel. 

LIQUA'TION  {liquo,  to  melt).  Eli- 
quation.  An  old  process  for  separating 
silver  from  copper.  During  reduction, 
the  silver  is  mixed  with  lead,  which  has 
little  affinity  for  the  copper,  but  combines 
readily  with  the  silver ;  the  lead  is  then 
separated  from  the  silver  by  cupellation. 

LIQUEFACTION  (liquefacio,  to  melt). 
The  passing  of  a  substance  from  the  solid 
to  the  liquid  state— one  of  the  effects  of 
caloric.  The  term  is  sometimes  syno- 
nymous with  fusion,  with  deliquescence, 
and  with  solution. 

LIQUID  {liqueo,  to  melt).  An  ine- 
lastic fluid,  the  particles  of  which  move 
on  each  other,  and  yield  to  the  slightest 
impression.  All  liquids  may  be  arranged 
into  two  great  classes,  viz.  simple  liquids, 
as  mercury,  and  compound  liquids,  as 
combined  gases,  &c. 

LI'THARGE  (X/0o?,  a  stone,  apyvpo?, 
silver).  A  semi-crystalline  protoxide  of 
lead,  obtained  in  the  process  of  sepa- 
rating silver  from  lead  ores.  Litharge 
199 


is  more  or  less  white  or  red  according  to 
the  metals  with  which  the  silver  is  al- 
loyed, the  white  being  called  litharge  of 
silver,  the  red  litharge  of  gold. 

LITHIA  (XiOos,  a  stone).  The  pro- 
toxide of  lithium;  an  alkaline  oxide 
existing  in  certain  minerals,  and  in  the 
waters  of  Carlsbad,  in  combination.  Its 
name  is  derived  from  its  occurring  only 
in  the  mineral  kingdom. 

LITHIC  ACID  (,\i'0op,  a  stone).  Uric 
acid.  A  principle  constantly  present  in 
healthy  urine,  and  generated  by  the 
action  of  the  kidneys. 

LFTHIUM  (\i0os,  a  stone).  A  metal 
first  found  in  the  minerals  petalite  and 
spodumene,  and  more  recently  in  ambly- 
gonite  and  lepidolite,  where  it  exists  in 
combination  with  silica. 

LITHO'DOMI  {XiOoi,  a  stone,  dep.<a, 
to  build).  Molluscous  animals  which 
form  holes  in  solid  rocks,  in  which  they 
lodge  themselves.  The  holes  are  not 
perforated  mechanically,  but  the  rock 
appears  to  be  dissolved. 

LITHO'GENOUS  (Ai'flor,  a  stone,  yev- 
vctco,  to  form).  A  term  applied  to  polyps 
which  form  coral. 

LITHOGRAPHIC  STONE  (\i9os,  a 
stone,  7pa0o>,  to  write).  A  slaty  com- 
pact limestone,  of  a  yellowish  colour  and 
fine  grain,  used  in  lithography. 

LITHOI'DAL  (\i6os,  a  stone,  ei3oy, 
likeness).  Having  a  structure  resembling 
stone. 

LITHOLO'GICAL  (\t'0oc,  a  stone,  \6- 
70?,  an  account).  A  term  denoting  the 
stony  structure  or  character  of  a  mineral 
mass.  The  lithological  character  of  a 
stratum  is  distinguished,  in  the  language 
of  geology,  from  its  zoological  character. 

LI'THOMARGE.  Steinmarck.  Stone- 
marrow,  a  mineral  which  has  been  asso- 
ciated with  steatite,  although  most  of  its 
varieties  are  silicates  of  alumina ;  the 
more  remarkable  of  which  are,  that  of  a 
reddish-yellow  colour  in  porphyry,  from 
Rochlitz,  and  the  fine  purplish-blue  va- 
riety from  Planitz,  formerly  called  terra 
miraculosa  Saxonica,  &c. 

LITHO'PHAGI  (Xiflot,  a  stone,  <pdyia, 
to  eat).  Molluscous  animals  which  form 
holes  in  solid  stones.    See  Lithodomi. 

LITHOPHA'GIDjE  (\ieos,  a  stone, 
<pdy<a,  to  eat).  A  general  designation  of 
those  conchiferous  and  other  animals, 
which  perforate  stones  or  corals,  forming 
therein  a  nidus,  or  shallow  basin-like 
lodgment  for  themselves. 

LITHO'PHYTA  (\iOos,  a  stone,  (pvrov, 
a  plant).  A  designation  of  those  polyps 
K4 


LIT 


LOC 


which  have  a  stony  axis,  as  distinguished 
from  the  keratophyta,  or  horny  polyps. 

LITMUS.  Turnsol,  A  blue  pigment 
obtained  from  the  Lichen  orcella,  and 
employed  by  chemists  for  detecting  the 
presence  of  an  uncombined  acid.  Litmus 
paper  is  prepared  by  digesting  pow- 
dered litmus  in  water,  and  painting 
with  it  white  paper  which  is  free  from 
alum. 

LI'TUUS.  The  name  given  to  a  spiral 
thus  described  :— Let  a  variable  cir- 
cular sector  always  have  its  centre  at 
one  fixed  point,  and  one  of  its  termi- 
nal radii  in  a  given  direction.  Let  the 
area  of  the  sector  always  remain  the 
same;  then  the  extremity  of  the  other 
terminal  radius  describes  the  lituus. 
The  polar  equation  of  this  spiral  is 
r*  0  =  a.— Pen.  Cycl. 

LIVER-ORE.  Hepatic  mercurial  ore. 
A  mixture  of  cinnabar  with  bituminous 
and  earthy  particles,  from  Idria,  compact 
and  slaty. 

LIVER-PYRITES.  Sulphuret  of  iron, 
of  a  radiated  texture  ;  distinct  from  the 
fer  sulphure  hepatique  of  some  French 
mineralogists,  which  cousists  of  both  ra- 
diated and  common  iron-pyrites  con- 
verted into  brown  iron-stone. 

LIXIVIA'TION  {lixivium,  a  ley).  The 
application  of  water  to  a  saline  body 
which  consists  of  both  soluble  and  inso- 
luble ingredients.  The  solution  obtained 
is  the  lixivium,  or  ley, — a  term  used  by 
the  older  chemists  to  signify  a  solution  of 
an  alkali  in  water ;  what  is  now  called 
an  alkaline  solution,  being  formerly 
called  an  alkaline  lixivium  or  ley. 

LLANDEILO  FLAGS.  The  name  of 
one  of  the  Lower  Silurian  Rocks,  con- 
sisting of  a  bed,  1200  feet  in  thickness, 
of  hard,  dark-coloured,  slaty  sandstones, 
frequently  calcareous,  sometimes  slightly 
micaceous,  containing  mollusca  and  tri- 
lobites. 

LOADSTONE.  An  ore  of  iron  which 
possesses  the  peculiar  properties  of  at- 
tracting iron,  and  of  turning  towards  the 
north  pole,  when  freely  suspended.  M. 
Haiiy  observes,  that  the  ores  in  which 
the  iron  contains  the  least  oxygen  inde- 
pendently of  other  combinations,  form 
natural  magnets ;  and  he  terms  the  load- 
stones of  commerce,  found  in  different 
parts  of  the  world,  oxidulated  iron.  The 
properties  of  the  natural  loadstone  may 
be  communicated  to  iron  and  steel,  which, 
when  properly  prepared  and  touched  by 
the  loadstone,  are  called  artificial  mag- 
nets. See  Magnet. 
200 


LOAM.  A  soil  consisting  chiefly  of 
clay,  silicious  sand,  and  chalk,  or  car- 
bonate of  lime.  The  quality  of  a  loamy 
soil  varies  considerably  with  the  relative 
proportions  of  these  constituents. 

LOAM  or  BRICK  CLAY.  A  variety 
of  clay  of  variable  appearance,  its  colour 
depending  on  the  proportion  of  oxide  of 
iron  which  it  contains.  It  lies  upon  the 
London  clay,  and  contains  a  few  organic 
remains,  sometimes  the  teeth  of  the  ele- 
phant. The  Hedgerley  loam,  found  near 
Windsor,  is  used  in  making  lutes,  &c. 

LOBELIA'CEiE.  The  Lobelia  tribe 
of  dicotyledonous  plants.  Herbaceous 
plants  or  shrubs,  with  leaves  alternate ; 
flowers  axillary  or  terminal;  stamens 
syngenesious ;  ovary  inferior ;  fruit  cap- 
sular. 

LO'BOITE.  A  magnesian  idocrase 
occurring  in  Norway. 

LOCOMO'TIVE  {locus,  place,  moveo, 
to  move).  A  term  generally  expressive 
of  motion  attended  by  a  change  of  place, 
and  thus  opposed  to  stationary:  thus,  a 
locomotive  power,  or  engine,  is  any  power 
or  engine  employed  for  transport,  which 
travels  with  the  load  it  draws. 

LOCULICI'DAL  {loculus,  a  cell,  ccedo, 
to  cut).  That  mode  of  dehiscence  of 
fruits,  in  which  the  loculi,  or  cells,  are 
severed  at  their  backs,  as  in  lilac.  The 
older  botanists  described  it  as  dehiscence 
with  the  valves  opposite  to  the  dissepi- 
ments. 

LO'CUS.  The  Latin  word  for  a  place. 
In  geometrical  analysis,  it  denotes  a  line 
or  surface  traversed  by  a  point  which  va- 
ries its  position  according  to  some  deter- 
minate law.  1.  The  locus  of  the  vertex 
of  an  isosceles  triangle  described  upon  a 
given  base,  is  the  straight  line  which  bi- 
sects the  base  at  right  angles.  2.  The 
locus  of  the  vertex  of  a  triangle  which 
has  a  given  base  and  a  given  area,  is  a 
pair  of  straight  lines  parallel  to,  but  on 
different  sides  of,  the  base.  3.  The  locus 
of  the  vertex  of  a  triangle  which  has  a 
given  base  and  a  given  vertical  angle, 
and  which  lies  on  a  given  side  of  the 
base,  is  an  arc  of  a  circle  of  which  the 
given  base  is  the  chord. 

1.  Plane  and  Solid  Loci.  "When  the 
locus  of  the  variable  point  is  a  straight 
line  or  a  circle,  it  was  called  by  the  an- 
cient geometers  a  plane  locus ;  when  one 
of  the  conic  sections,  a  solid  locus. 

2.  Orders  of  Loci.  Loci  are  distin- 
guished into  orders  or  degrees,  according 
to  the  dimensions  of  the  algebraic  equa- 
tions  by  which   they   are   represented. 


LOC 


LOG 


The  loci  of  all  equations  of  the  second 
degree  are  conic  sections  or  circles. 

LOCU'STA.  In  Botany,  a  spikelet,  or 
the  partial  inflorescence  of  certain  grasses, 
as  the  brome  and  the  wheat.  This  term 
is  also  applied  to  those  other  inflores- 
cences, in  which  the  flowers  are  sessile, 
and  arranged  upon  a  lengthened  axis, 
which  is  permanent ;  it  is  thus  distin- 
guished from  the  catkin,  which  is  deci- 
duous. 

LOCU'STIC  ACID.  An  acid  procured 
from  the  locusta,  or  grasshopper,  differ- 
ing little  from  acetic  acid. 

LOCU'STID^E  {locusta,  a  locust).  The 
Locust  tribe;  a  group  of  Orthopterous 
insects,  belonging  to  the  class  Saltatoria, 
remarkable  for  their  migratory  habits 
and  devastating  powers. 

LODE.  A  technical  term  for  a  metallic 
or  mineral  vein.  Live  lodes  are  those 
which  contain  metallic  ores ;  dead  lodes, 
those  which  contain  only  stony  matters. 

LOESS,  or  LOSS.  A  German  desig- 
nation of  a  peculiar  loamy  deposit  in  the 
valley  of  the  Rhine,  occurring  in  patches 
between  Cologne  and  Basle.  The  term 
is  sometimes  applied  in  this  country  to 
a  peculiar  yellow  loam  with  calcareous 
concretions.  > 

LOG  and  LOG-LINE.  The  Log,  in 
sea-language,  is  the  name  of  a  piece  of 
wood  in  the  form  of  the  sector  (usually  a 
quadrant)  of  a  circle  of  Ave  or  six  inches 
radius.  It  is  about  a  quarter  of  an  inch 
thick,  and  so  balanced  by  means  of  a  plate 
of  lead  nailed  upon  the  circular  part,  as  to 
swim  perpendicularly  in  the  water  with 
about  two-thirds  immersed  under  the 
surface.  The  Log-line  is  a  small  cord  of 
about  one  hundred  fathoms  in  length, 
one  end  of  which  is  fastened  (by  means  of 
two  legs)  to  the  centre  and  to  the  arched 
part  of  the  Log,  while  the  other  is  wound 
round  a  reel  in  the  gallery  of  the  ship. 
The  Log  thus  poised  keeps  its  place  in 
the  water  while  the  line  is  unwound  from 
the  reel  by  the  ship's  sailing;  and  the 
length  of  line  unwound  in  a  given  time 
gives  the  rate  of  the  ship's  course.  This 
is  calculated  by  knots  made  on  the  line 
at  between  forty  and  fifty  feet  distance, 
while  the  time  is  measured  by  a  sand- 
glass of  a  certain  number  of  seconds. 
The  length  between  the  knots  is  so  pro- 
portioned to  the  time  of  the  glass,  that 
the  number  of  knots  unwound  shows  the 
number  of  miles  which  the  ship  is  sailing 
in  the  hour. 

LO'GARITHM  (\6yo?,  a  ratio,  3p<0- 
/uor,  number).  Logarithms  are  a  series 
201 


of  numbers  adapted  in  a  certain  way  to 
a  series  of  natural  numbers,  to  facilitate 
the  processes  of  numerical  computation. 
A  simple  idea  of  this  system  may  be  ac- 
quired by  taking  a  set  of  numbers,  as 
1,  2,  3,  4,  5,  6,  having  for  their  common 
difference  the  first  number  of  the  series ; 
and  placing  under  them  another  set  of 
numbers,  which  proceed  by  continued 
multiplication  by  the  first  number  of  the 
series,  as  2,  4,  8,  16,  32,  64.  The  former 
set  are  the  logarithms  of  the  latter,  which 
are  called  natural  numbers.    Thus, 

1,  2,  3,    4,     5,    6,   &c. 

2,  4,  8,  16,  32,  64,    &c. 

1.  If  now  we  add  together  any  two  of 
the  upper  set,  and  note  the  number  be- 
neath their  sum  in  the  lower  set,  this 
number  represents  the  product  arising 
from  multiplying  together  the  numbers 
of  the  lower  set  corresponding  with  the 
numbers  of  the  upper  set  which  were 
added  together.  Thus,  on  adding  2  to  4, 
we  have  6  in  the  upper  set,  beneath 
which  is  64 ;  and  this  is  the  product  of 
4  and  16  in  the  lower  set,  opposite  to  2 
and  4  in  the  upper.  So  that,  instead  of 
multiplying  the  natural  numbers,  we  add 
their  logarithms  together,  and  at  once  find 
the  product. 

2.  In  like  manner,  if  we  subtract  one 
of  the  upper  numbers  from  another,  and 
note  the  number  beneath  their  difference 
in  the  lower  set,  this  number  represents 
the  quotient  arising  from  the  division  of 
one  of  the  lower  numbers  by  another, 
both  corresponding  with  the  upper  num- 
bers which  were  subjected  to  the  process 
of  subtraction.  Thus,  on  subtracting  4 
from  6,  we  have  2  in  the  upper  set,  be- 
neath which  is  4 ;  and  this  is  the  quotient 
arising  from  the  division  of  64  (the  num- 
ber beneath  6)  by  16  (the  number  beneath 
4).  So  that,  instead  of  dividing  the  natu- 
ral numbers,  we  subtract  their  logarithms, 
and  at  once  find  the  quotient. 

3.  By  the  aid  of  logarithmic  tables, 
time  and  labour  are  saved  to  an  extraor- 
dinary degree.  Supposing,  for  instance, 
we  had  to  multiply  a  number,  consisting 
of  seven  figures  by  itself,  and  this  pro- 
duct again  by  the  original  number,  we 
shall  have  to  multiply  seven  places  of 
figures  by  an  equally  large  number,  and 
then  fourteen  places  of  figures  by  seven 
places,  till  at  last  we  reach  a  product 
of  twenty-one  places.  But,  by  the  aid  of 
logarithms,  we  have  only  to  take  three 
times  the  logarithm  of  the  original  num- 
ber, and  that  gives  the  logarithm  of  the 

KS 


LOG 

last  product  of  the  21  places  of  figures, 
without  any  further  multiplication. 

4.  The  index  or  characteristic  of  the 
logarithm  of  a  number  is  one  less  than 
the  number  of  integral  figures  of  the 
number.  Thus,  if  the  number  contain 
five  integral  figures,  the  index  is  4  ;  if  it 
contain  four,. the  index  is  3;  and  so  on. 
When  the  number  has  no  integral  figures, 
the  index  of  its  logarithm  is  negative, 
and  is  one  more  than  the  number  of  ci- 
phers immediately  after  the  decimal 
place;  that  is,  the  number  of  prefixed 
ciphers.  Thus,  if  there  is  no  cipher  after 
the  decimal,  the  index  is  — 1 ;  if  there  is 
one  prefixed  cipher,  the  index  is  — 2  ;  and 
so  on.  The  negative  sign  is  placed  over 
the  index,  thus  :  ~T,  ~2,  &c. 

5.  The  logarithm  of  a  number  to  a  given 
base  is  the  quantity  expressing  the  power 
to  which  the  base  must  be  raised  to  be- 
come equal  to  the  number. 

6.  Logarithmic  Curve  and  Logarithmic 
Spiral.  "  The  former  has  for  its  rectan- 
gular equation  y  =  ax,  and  its  most  re- 
markable property  is  that  its  subtangent 
is  the  same  at  every  point  of  the  curve. 
The  latter  has  r  =  ca®  for  its  polar  equa- 
tion, and  its  tangent  always  makes  the 
same  angle  with  its  radius  vector ;  whence 
it  is  called  the  equiangular  spiral." — Pen. 
Cycl. 

LOGIC  (\oytKtj  Te%vfi,  the  art  of  rea- 
soning). Logic,  in  its  most  extensive 
application,  is  the  science,  as  well  as  the 
art,  of  reasoning.  So  far  as  it  institutes 
an  analysis  of  the  process  of  the  mind  in 
reasoning,  it  is  strictly  a  science;  while, 
so  far  as  it  investigates  the  principles  on 
which  argumentation  is  conducted,  and 
furnishes  rules  to  secure  the  mind  from 
error  in  its  deductions,  it  may  be  called 
the  art  of  reasoning. —  Whately. 

LONDON  CLAY.  An  extensive  de- 
posit of  a  bluish  clay,  except  near  the 
surface,  where  it  has  the  usual  appearance 
of  clay.  It  abounds  in  Middlesex,  Essex, 
Suffolk,  and  part  of  Norfolk.  It  occa- 
sionally includes  beds  of  sandstone,  and 
of  a  coarse  argillaceous  limestone,  from 
which  Parker's  Roman  cement  is  made. 
It  contains  also  the  bones  of  the  crocodile, 
the  turtle,  &c. 

LONGICO'RNES  {longus,  long,  cornu, 
a  horn).  A  family  of  the  tetramerous 
Coleoptera,  characterized  by  the  great 
development  of  the  antennae,  which 
are  often  longer  than  the  body  of  the 
animal. 

LONGIPE'NNES  {longus,  long,  penna, 
a  feather).  A  family  of  long-winged 
202 


LOO 

oceanic  birds,  comprising  the  albatross, 
the  petrel,  &c. 

LONGITUDE  {longitudo,  length).  1. 
The  longitude  of  a  heavenly  body  is 
measured  on  an  arc  of  the  ecliptic,  inter- 
cepted between  the  vernal  equinoctial 
point  and  a  great  circle  passing  through 
the  body,  and  perpendicular  to  the 
ecliptic.  2.  The  longitude  of  a  place  on 
the  earth's  surface  is  the  inclination  of 
its  meridian  to  that  of  some  fixed  station 
referred  to  as  a  point  to  reckon  from. 
English  astronomers  and  geographers 
use  the  observatory  at  Greenwich  for  this 
station ;  foreigners,  the  principal  ob- 
servatories of  their  respective  nations. 
The  terms  longitude  and  latitude  were 
employed  in  Geography  from  an  idea 
of  the  ancients  that  the  earth  was  longer 
from  east  to  west  than  from  north  to 
south ;  the  former  dimension  was  called 
its  length,  the  latter  its  breadth. 

1.  Proposed  Change  of  Expression.  As 
latitude  is  reckoned  north  or  south,  so 
longitude  is  usually  said  to  be  reckoned 
west  or  east.  "It  would  add  greatly, 
however,  to  systematic  regularity,  and 
tend  much  to  avoid  confusion  and  am- 
biguity in  computations,  were  this  mode 
of  expression  abandoned,  and  longitudes 
reckoned  invariably  westward  from  their 
origin  round  the  whole  circle  from  0  to 
360°.  Thus,  the  longitude  of  Paris  is, 
in  common  parlance,  either  2°  20'  22" 
east,  or  357°  39'  38"  west  of  Greenwich. 
But  the  latter  is  its  proper  designation." 
— Herschel. 

2.  Longitude  in  Time.  Longitude  is 
reckoned  in  time  at  the  rate  of  24  hours 
for  360°,  or  15°  per  hour.  Thus  the 
longitude  of  Paris  is  23h.  50m.  38£s. 
Hence,  by  longitude  in  time  is  denoted 
the  difference  in  time  in  which  two 
places,  situated  east  and  west  of  each 
other,  see  the  same  heavenly  bodies :  a 
place  15°  east  of  us  sees  the  sun  and 
stars  an  hour  earlier  than  we  do ;  at  the 
same  distance  west,  an  hour  later. 

LONGITU'DINAL  {longitudo,  length). 
Lengthwise ;  that  which  has  a  perpen- 
dicular direction  from  the  apex  to  the 
base  of  a  body,  as  contradistinguished 
from  the  term  "transverse,"  which  de- 
notes a  direction  across  its  breadth. 

LONGITUDINAL  VALLEYS.  The 
name  given  by  Saussure  to  the  great 
valleys  which  separate  the  mountain- 
chains,  and  give  passage  to  rivers,  as 
that  of  the  Danube,  those  of  the  Rhine 
and  the  Rhone,  &c. 

LOOKING-GLASSES.    Plain  mirrors 


LOP 


LUN 


of  glass,  which,  being  impervious  to  the 
light,  reflect  the  images  of  things  placed 
before  them. 

LO'PHIODON  (\6<pos,  a  crest.  o<3ot/?, 
a  tooth).  A  genus  of  extinct  pachyderms, 
allied  to  the  tapir,  and  named  from  emi- 
nences of  the  teeth.  They  are  known 
only  by  imperfect  fragments. 

LOPHOBRA'NCHII  (X6</>or,  a  crest  or 
tuft,  /3pa7x«*»  gills).  An  order  of  Fishes, 
in  which  the  gills,  instead  of  hanging  in 
regular  fringes,  like  the  teeth  of  a  comb, 
from  the  branchial  arches,  are  disposed 
in  tufts,  as  in  the  pipe-fish,  &c. 

LORPCA.  Literally,  a  coat  of  mail. 
A  kind  of  lute,  with  which  vessels  are 
coated  before  they  are  exposed  to  the 
fire.  Hence  the  term  lorication  in  che- 
mistry, for  coating.     See  Lute. 

LORICA'TA  {lorica,  a  coat  of  mail). 
1.  An  order  of  Reptiles,  including  the 
crocodiles,  alligators,  and  gavials,  inter- 
mediate between  the  fresh- water  tortoises, 
and  the  true  lizards,  and  characterized 
by  the  plate-armour  with  which  their 
body  is  protected.  2.  Also,  a  group  of 
polygastric  animalcules,  enclosed  in  a 
shell,  and  thus  distinguished  from  the 
group  termed  nuda,  in  which  the  body  is 
entirely  soft. 

LOWER  GREENSAND.  The  geo- 
logical designation  of  the  early  deposits 
of  the  Cretaceous  Period,  consisting,  in 
England,  principally  of  sand,  varied  oc- 
casionally by  calcareous  and  muddy 
bands ;  but  on  the  Continent  including 
many  beds  of  limestone.  See  Neoco- 
mian. 

LO'XIKDM.  The  Cross-bill  tribe;  a 
family  of  the  Insetsores,  or  Perching  birds, 
named  from  the  genus  loxia,  and  charac- 
terized by  the  strong  curvature  of  the 
mandibles,  which  is  carried  to  such  an 
extent  that  the  extremities  pass  over 
each  other.    See  Conirostres. 

LOXODRO'MIC  CURVE  (\oS6s,  ob- 
lique, apogee,  a  course).  A  term  applied 
to  a  curve  of  a  very  peculiar  nature, 
commonly  called,  in  Navigation,  the 
oblique  rhumb  line.  It  is  a  spiral,  and 
has  the  remarkable  property  of  winding 
round  and  round  the  pole  of  the  earth, 
constantly  approaching,  yet  never  reach- 
ing it ;  so  that,  if  a  ship  could  sail  on  the 
same  oblique  course  for  ever,  she  would 
approach  infinitely  near  either  to  the 
north  or  the  south  pole,  but  could  never 
actually  reach  them.    See  Rhumb  Line. 

LUCERNl'NUE.  Land  Volutes,  or 
Lamp  snails ;  a  sub-family  of  the  Heli- 
cidce,  named  from  the  genus  lucerna,  and 
203 


having  an  orbicular,  depressed,  or  flat- 
tened shell,  with  the  aperture  furnished 
with  distinct  teeth. 

LUCU'LLITE.  A  sub-species  of  lime- 
stone, of  which  there  are  three  kinds, 
the  compact,  the  prismatic,  and  the  fo- 
liated. The  name  was  derived  from  the 
consul  Lucullus.  It  is  the  Nero  antico 
of  the  Italians. 

LUDLOW  ROCKS.  A  portion  of  the 
Upper  Silurian  rocks,  2000  feet  in  thick- 
ness, composed  of  three  groups  : — 1.  The 
Lower  Ludlow  Rock,  or  Mudstone,  con- 
sisting of  sandy,  dark-coloured  shales 
and  flags,  with  concretions  of  earthy 
limestone,  and  containing  marine  mol- 
lusca,  corals,  and  fishes;  2.  The  Ayme- 
stry  Limestone,  grey  or  bluish  argillaceous 
limestone,  full  of  remains  of  shells  and 
corals;  and,  3.  The  Upper  Ludlow  Rock, 
thin,  grey,  slightly  micaceous  sandstones 
and  shales,  containing  shells  and  trilo- 
bites. 

LUMACHE'LLA,  CARINTHIAN. 
Fire  marble;  a  variety  of  shell  lime- 
stone, much  esteemed  for  ornamental 
purposes. 

LUMIE'RE  CENDRE'E.  The  ashy 
light;  a  term  applied  by  the  French  to 
the  feeble  lustre  observable  on  the  un- 
illuminated  portion  of  the  moon,  arising 
from  the  light  reflected  upon  her  from 
the  earth.  It  is  popularly  called,  in  this 
country,  the  old  moon  in  the  new  moon's 
arms. 

LUNA.  The  Moon;  the  satellite  of 
the  Earth,  being  the  fiftieth  part  of  the 
bulk  of  this  planet,  and  230,000  miles 
distant  from  it.  She  revolves  round  the 
earth  in  29  days,  12  hours,  44  minutes, 
2  seconds,  turning  upon  her  own  axis 
precisely  in  the  same  time  as  she  takes 
to  revolve  round  the  earth. 

LUNA  CORNEA.  Horn  silver;  the 
chloride  of  silver,  so  named  from  its 
horn-like  appearance  and  consistence. 
Luna  was  the  alchemical  name  for 
silver. 

LUNAR  DISTANCE.  In  nautical 
astronomy,  the  distance  of  the  moon  from 
the  sun,  a  fixed  star,  or  a  planet ;  by  de- 
termining this,  the  longitude  of  the  ship 
is  found. 

LUNATE  (luna,  the  moon).  Present- 
ing the  form  of  a  crescent  or  half-moon, 
as  the  muscular  impressions  of  most 
bivalves. 

LUNA'TION  {luna,  the  moon).    The 

interval  from  one  new  moon  to  another. 

This  is  the  original  month,  but,  to  avoid 

confusing  it  with  the  arbitrary  months 

K6 


LUN 


MAC 


of  the  calendar,  it  is  generally  called  a 
lunation. 

LUNE  (luna,  the  moon).  Lunule. 
The  spherical  surface  included  between 
two  semicircles  ;  or,  the  figure  described 
on  a  sphere  or  on  a  plane  by  two  arcs  of 
circles  which  enclose  a  space. 

LU'NULITES  {lunula,  a  little  moon, 
XiOot,  a  stone).  A  genus  of  fossil  cella- 
riadce,  consisting  of  animals  (unknown) 
contained  in  cellules,  and  arranged  in 
single  tiers,  so  as  to  form  orbicular  poly- 
paria. 

LUPUS.  The  Wolf;  a  southern  con- 
stellation, consisting  of  twenty -four  stars, 
and  represented  in  maps  as  a  wolf  trans- 
fixed by  the  spear  of  the  Centaur.  It  is 
situated  directly  beneath  Scorpius. 

LUSTRE  of  ROCKS.  This  is  one  of 
the  distinguishing  characters  of  rocks. 
According  to  Mac  Culloch,  the  highest  de- 
gree of  lustre  is  the  plumbaginous,  or 
that  of  graphite  or  black  lead,  which  is 
seen  in  some  clay-slates.  The  other  ex- 
treme is  that  of  chalk,  which  is  dull,  or 
almost  destitute  of  lustre.  The  principal 
intermediate  kinds  are  the  silky,  resin- 
ous, vitreous,  flinty,  and  waxy. 


LUTE.  A  compound  paste,  made  of 
clay,  sand,  &c,  for  closing  retorts  and 
receivers,  in  order  to  render  them  air- 
tight. 

LYCOPODIA'CEjE.  The  Club-moss 
tribe  of  flowerless  plants,  characterized 
by  their  creeping  stems,  the  axis  abound- 
ing in  annular  ducts.  Reproductive  or- 
gans are  axillary  sessile  thecse,  containing 
either  minute  powdery  matter,  or  sporules 
marked  at  the  apex  with  three  minute 
ridges. 

LYCO'PODITES.  A  general  term  for 
those  fossil  plants  which  correspond  in 
some  of  their  characters  with  some  of  the 
genera  composing  the  Lycopodiacese. 

LYDIAN  STONE.  Flinty  slate;  a 
kind  of  quartz  or  flint,  allied  to  horn- 
stone,  but  of  a  greyish  black  colour.     . 

LYE  or  LEY.  A  solution  of  potass,  or 
other  alkaline  substance,  used  in  the 
arts.    See  Lixiviation. 

LYMPH  (lympha,  water).  A  colour- 
less liquid  which  moistens  the  surface  of 
cellular  membrane.  The  lymph  of  plants 
is  the  unelaborated  sap,  so  called  from 
its  resemblance  to  water. 


M 


MAASTRICHT  ROCKS.  These  rocks 
are  considered  by  geologists  as  an  upper 
part  of  the  chalk  formation  ;  and  then- 
place  in  the  scale  of  strata  is  in  imme- 
diate superposition  above  the  chalk  of 
England,  and  at  some  small  interval  be- 
low the  calcaire  grossier  of  the  Paris 
basin. 

MACE.  The  external  envelope  of  the 
seed  of  the  myristica  moschata,  affording 
an  interesting  example  of  an  arillus,  or 
expansion  of  the  placenta. 

MACERA'TION  (macero,  to  make 
soft  by  steeping).  The  steeping  of  ani- 
mal or  vegetable  substances  in  a  cold 
liquid,  for  the  purpose  of  softening  the 
parts  previously  to  distillation,  or  for 
that  of  dissolving  their  aromatic  prin- 
ciples. 

MA'CHINA  PNEUMA'TICA.  The 
Pneumatic  Machine ;  a  modern  southern 
constellation,  consisting  of  three  stars. 

MACHINE  {machina,  a  frame  or  con- 
trivance). Any  instrument  by  which 
power,  motion,  or  velocity,  is  applied  or 
regulated.  The  force  which  puts  a  ma- 
chine in  motion  is  called  the  first  or 
prime  mover.  The  point  at  which  that 
204 


force  is  applied  is  the  acting  point;  and 
that  at  which  the  effect  is  produced  is 
the  working  point;  the  machine  being 
the  medium  through  which  the  power  is 
transferred,  and  by  which  it  is  modified 
so  as  to  answer  the  intended  purpose. 
When  a  simple  body  is  the  medium  be- 
tween the  acting  and  the  working  points, 
it  is  an  instrument. 

MACI'GNO.  The  Italian  term  for  a 
hard  siliceous  sandstone,  sometimes  con- 
taining calcareous  grains,  mica,  &c. 

MA'CLE.  Chiastolite.  A  mineral  found 
imbedded  in  clay-slate,  in  the  Pyrenees, 
and  consisting  principally  of  silica  and 
alumina. 

MACLU'REITE.  Chondrodite  or  bru- 
cite.  A  mineral  substance  consisting  of 
a  silicate  of  magnesia  with  other  matters, 
occurring  in  New  Jersey  and  at  Pargas 
in  Finland,  and  named  after  Dr.  Maclure. 

MACQUER'S  SALT.  Neutral  arseni- 
cal salt ;  super-arseniate  of  potass. 

MACROCEPHALOUS  (MaKP6p,  large, 
K€(pa\rj,  the  head).  Large-headed;  a 
term  applied  by  Richard  to  those  dico- 
tyledonous embryos,  in  which  the  two 
cotyledons  cohere,  as  in  horse-cheatnut. 


MAC 


MAG 


Gartner  terms  these  embryos  pseudo- 
monocotyledonous, 

MA'CROCOSM  (/laKpo?,  large,  Ko<rjuo9, 
the  world).  A  term  employed  as  synony- 
mous with  universe;  while  microcosm 
has  been  used  by  some  philosophers  as 
a  designation  of  man. 

MACRODA'CTYLES  (/jLanpos,  large, 
ddnTv\os,  a  finger  or  toe).  A  tribe  of  the 
Grallatores,  or  wading  birds,  charac- 
terized by  the  extreme  length  of  their 
feet. 

MACRO'PODAL  (juaxpo?,  large,  ttovs, 
7Tod6?,  a  foot).  Large-footed;  a  term 
applied  by  Richard  to  a  modification  of 
the  monocotyledonous  embryo,  in  which 
the  radicle  presents  an  unusual  protu- 
berance, as  in  wheat. 

MACROPO'DIANS  (nanpos,  large, 
irovs,  Trodor,  a  foot).  A  tribe  of  brachyu- 
rous  decapod  crustaceans,  remarkable  for 
the  enormous  length  of  their  feet,  which 
has  procured  for  them  the  name  of  sea- 
spiders. 

MACROTRA'CHIA.  A  tribe  of  bi- 
valved  mollusca,  in  which  the  mantle  of 
the  animal  is  so  united  and  prolonged  as 
to  form  one  or  two  long  siphons  or  tubes, 
by  which  the  food  is  imbibed. 

MACROU'RA  (/LiaKpor,  large,  otpa,  a 
tail).  A  family  of  decapod  Crustacea, 
distinguished  by  the  large  size  of  the  tail, 
as  in  the  common  lobster. 

MA'CULiE  (macula,  a  spot).  Dark 
spots  frequently  seen  on  the  disc  of  the 
sun.  They  change  their  appearance  as 
the  sun  revolves  on  his  axis,  and  appear 
greater  or  less  to  an  observer  on  the 
earth,  as  they  are  turned  to  or  from  him. 
One  of  these  was  estimated  to  be  more 
than  six  times  the  size  of  our  earth. 

MA'DREPORE.  A  genus  of  corals  ; 
but  the  term  is  generally  applied  to  all 
the  corals  distinguished  by  superficial 
star-shaped  cavities.  In  zoological  lan- 
guage, the  madrepores  are  compound 
polyps,  the  common  body  of  which  se- 
cretes calcareous  matter  on  its  exterior 
in  arborescent  masses,  presenting  upon 
their  surface  multitudes  of  cells,  in  each 
of  which,  when  alive,  a  polyp  existed. 

MA'DREPORITE.  Anthraconite.  Co- 
lumnar carbonate  of  lime,  found  in  Nor- 
way in  transition  rocks,  in  Greenland,  &c. 

MAGDEBURG  HEMISPHERES.  An 
apparatus  for  exhibiting  the  force  of  the 
atmospheric  pressure.  Two  hollow  me- 
tallic hemispheres,  whose  edges  fit  accu- 
rately, are  placed  on  each  other,  and  the 
air  is  exhausted.  Supposing  the  super- 
ficial content  to  be  100  square  inches,  and 
205 


the  height  of  the  mercury  to  be  30  inches, 
the  pressure  exerted  on  the  hemispheres 
will  amount  to  1475  lbs.,  and  it  will  re- 
quire the  force  of  two  horses  to  pull  them 
asunder. 

MAGELLA'NIC  CLOUDS.  The  name 
of  three  nebulae  in  the  southern  hemi- 
sphere, two  of  them  about  12°  or  13° 
from  the  south  pole,  the  third  more  dis- 
tant. They  were  first  recorded  by  the 
navigator  Magellan. 

MAGIC  LANTERN.  The  magic  lan- 
tern is  a  microscope,  on  the  same  prin- 
ciple as  the  solar  microscope.  But  in- 
stead of  being  used  to  magnify  natural 
objects,  it  is  commonly  employed  for 
amusement,  by  the  casting  of  shadows 
of  small  transparent  paintings,  done  on 
glass,  upon  a  screen  placed  at  a  proper 
distance. 

MAGIC  SQUARE.  A  series  of  num- 
bers in  arithmetical  progression,  so  ar- 
ranged in  a  square  order,  that  the  vertical, 
horizontal,  and  diagonal  columns  give 
the  same  sum.    Thus : 


1 

2 

3 

4 

1 

16 

11 

6 

5 

6 

7 

8 

or 

13 

4 

7 

10 

9 

10 

11 

12 

8 

9 

14 

3 

13 

14 

15 

16 

12 

5 

2 

15 

MA'GISTERY  (magister,  a  master). 
A  masterly  preparation,  formerly  applied, 
in  Chemistry,  to  all  precipitates,  but  now 
restricted  to  a  few  substances,  as  the 
magistery,  or  subnitrate,  of  bismuth,  a 
brilliant  white  powder  of  pearly  lustre, 
composed  of  microscopic  crystalline 
grains  ;  the  magistery  of  silver,  the  alche- 
mical name  of  the  nitrate  ;  &c. 

MAGNE'SIA.  An  alkaline  earth, 
having  a  metallic  base,  called  magnesium. 
It  has  been  found  native,  in  the  state  of 
a  hydrate.  The  term  magnesia  was  ori- 
ginally applied  to  any  substance  which 
had  the  property  of  attracting  some  prin- 
ciple from  the  air. 

MAGNESIAN  LIMESTONE.  An 
extensive  series  of  beds,  lying  imme- 
diately above  the  Coal  Measures,  and  so 
named  from  the  presence  of  a  large  quan- 
tity of  magnesia  in  the  limestone.  It 
contains  fossils,  and  among  them  a  few 
corals  and  shells. 

MAGNE'SITE.  Carbonate  of  mag- 
nesia; a  white,  hard,  compact  mineral, 
found  in  Moravia,  in  serpentine  rocks. 

MAGNE'SIUM.  A  metallic  substance, 
resembling  silver,  fusing  at  a  red  heat, 
and  then,  on  burning  in  air  or  oxygen, 


MAG 


MAG 


producing  magnesia,  or  oxide  of  magne- 
sium, which  is  white,  inodorous,  and 
forms  an  ingredient  in  many  rocks,  to 
which  it  usually  communicates  a  soapy 
or  greasy  feel. 

MAGNET.  Magnets  are  suhstances 
which  attract  certain  metals;  which  dis- 
play towards  one  another  a  force  partly 
attractive  and  partly  repulsive;  and, 
lastly,  which  exhibit  a  tendency  to  ar- 
range their  mass  in  a  certain  direction 
{see  Pole).  The  term  is  probably  derived 
from  Magnesia,  owing  to  the  native  iron 
ore,  or  loadstone,  having  been  found  in 
abundance  near  that  city. 

1.  Magnet,  Natural  and  Artificial.  1. 
The  natural  magnet,  or  loadstone,  is  a 
chemical  combination  of  the  oxide  and 
the  suboxide  of  iron.  It  occurs  in  the 
northern  parts  of  the  world,  where  it 
forms  entire  mountains.  2.  Artificial 
magnets  are  commonly  of  steel,  to  which 
the  magnetfy  properties  are  communi- 
cated by  a  particular  process.  They  are 
of  various  forms  :  if  cylinders  or  parallel- 
opipeds,  they  are  called  bar  magnets ;  if 
curved  in  the  middle,  so  as  to  bring  the 
two  ends  near  together,  they  form  horse- 
shoe magnets ;  when  several  bars  or  horse- 
shoes are  combined,  the  apparatus  is 
called  a  compound  magnet,  or  a  magnetic 
battery,  or,  more  simply,  a  bundle  of  mag- 
nets. Those  artificial  magnets  which  are 
constructed  so  as  to  move  freely,  and 
which  will  then  invariably  assume  a 
certain  definite  position  with  respect  to 
the  earth,  are  called  needles. 

2.  Magnetic  North.  A  term  applied 
to  the  direction  of  the  magnetic  needle, 
which,  though  commonly  said  to  point  to 
the  north,  usually  points  some  degrees 
from  it,  one  way  or  the  other.  For  in- 
stance, all  along  the  line  which  passes 
through  the  Cape  de  Verd  Islands,  the 
magnetic  north  is  15°  west  of  the  true 
meridian ;  and  hence,  a  ship  on  this  line, 
wanting  to  sail  any  particular  course, 
steers  15°  wrong  by  her  compass  to  be 
right  by  the  meridian. 

3.  Magnetic  Indifference,  Point  of. 
That  point  of  a  magnet,  somewhere 
about  midway  between  the  two  extre- 
mities, where  the  attractive  force,  after 
continually  diminishing  as  we  proceed 
from  either  pole,  ceases  altogether. 

4.  Magnetic  Fluid.  The  hypothetical 
agent,  to  which  the  phenomena  of  mag- 
netism have  been  referred.  Some  have 
supposed  two  such  fluids,— a  boreal  or 
northern,  and  an  austral  or  southern. 
The  former  of  these  is  also  distinguished  as 

206 


positive,  the  latter  as  negative  magnetism, 
neither  of  which,  however,  is  found  singly 
combined  with  the  particles  of  matter, 
but  always  both  together. 

5.  Magnetic  Curves.  The  curved  lines 
into  which  iron-filings  arrange  them- 
selves when  dropped  gently  on  a  plate  of 
glass  having  a  magnet  beneath  it.  The 
filings  will  be  found  to  accumulate  most 
perceptibly  about  the  poles  of  the  magnet, 
and  to  arrange  themselves  in  curved  lines 
extending  from  one  pole  to  the  other. 

6.  Magnetic  Induction.  That  property 
by  which  each  pole  of  a  magnet  excites 
magnetism  in  any  magnetizable  body 
within  a  certain  distance  of  itself,  im- 
parting an  opposite  polarity  to  its  own  to 
the  contiguous  end  of  such  a  body,  and 
similar  polarity  to  its  remote  end.  The 
range  within  which  the  magnet  exerts  an 
influence  is  termed  its  circle  of  magnetic 
influence,  or  its  magnetic  atmosphere. 

7.  Magnetic  Points  of  Convergence. 
The  name  given  to  two  points,  near  to 
the  north  and  south  poles  of  our  planet, 
around  which  are  drawn  the  isogonic 
lines,  or  lines  of  equal  declination.  The 
two  points  are  also  called  the  magnetic 
poles  of  the  earth. 

8.  Magnetic  Equator.  The  name  of  an 
irregular  curve  in  the  neighbourhood  of 
the  terrestrial  equator,  where  a  needle 
balances  itself  perfectly  horizontally.  It 
is  also  called  the  aclinic  line. 

9.  Magneto-electrical  Rotatory  Machine. 
An  apparatus  for  rendering  the  magneto- 
electric  induction  currents  continuous, 
and  for  converting  their  alternating  di- 
rection into  a  constant  one.  Such  a 
machine  may  be  employed  as  a  substitute 
in  part  for  a  common  electrical  machine, 
and  in  part  also  for  a  voltaic  pile,  as  it  is 
capable  of  producing  electric  sparks,  in- 
candescence and  fusion  of  wire,  intense 
light  at  charcoal  points,  physiological 
effects,  chemical  decomposition,  and 
magnetic  action  of  many  kinds. 

MAGNET,  ARSENICAL.  A  corro- 
sive preparation  of  equal  parts  of  sulphur, 
white  arsenic,  and  common  antimony, 
mixed  by  fusion. 

MAGNETIC  PYRI'TES.  Native 
black  sulphuret  of  iron.  It  attracts  the 
magnetic  needle. 

MA'GNETISM.  A  term  expressing 
the  peculiar  property  occasionally  pos- 
sessed by  certain  bodies,  more  especially 
by  iron  and  some  of  its  compounds,  by 
which,  under  certain  circumstances,  they 
mutually  attract  or  repel  one  another,  ac- 
cording to  determinate  laws.  See  Magnet. 


MAG 


M  AL 


MAGNETO-ELECTRICITY.  A  term 
applied  to  those  electric  phenomena  which 
may  be  produced  by  magnetism. 

MAGNETO'METER.  The  term  ap- 
plied by  Gauss  to  a  magnetic  apparatus 
consisting  of  bars  of  iron  from  one  to 
four  feet  in  length,  and  weighing  from 
1  lb.  to  25  lbs.  These  masses  are  not 
affected,  like  the  needle,  by  variations  of 
temperature,  nor  by  the  presence  of 
other  similar  bodies,  while  at  the  same 
time  they  are  capable  of  indicating  the 
minutest  variations  in  the  intensity  of 
the  earth's  magnetism,  by  changes  in  the 
position  of  the  magnetometer,  which  can 
be  measured  to  an  angle  of  one  second. 

MAGNE'TOMO'TOR.  A  voltaic  se- 
ries of  two  or  more  large  plates,  for  pro- 
ducing a  great  quantity  of  electricity  of 
low  tension,  and  thus  exhibiting  the 
phenomena  of  electro-magnetism. 

MAGNIFYING  GLASS.  A  convex 
lens,  which  increases  the  apparent  size 
of  objects  viewed  at  a  small  distance 
through  it.  It  is  also  termed  a  burning 
glass,  because,  when  the  sun's  rays  are 
brought  to  a  point,  after  passing  through 
a  lens  of  this  kind,  they  produce  a  strong 
heat. 

MA'GNITUDE  (magnitudo,  size).  The 
general  term  for  quantity  of  space.  In 
Geometry,  it  denotes  the  space  occupied 
by  any  figure,  and  has  relation  to  the 
three  dimensions  of  length,  breadth,  and 
thickness.  It  may,  in  fact,  be  applied  to 
any  thing  which  involves  the  question  of 
"greater  or  less." 

1.  When  one  magnitude  is  compared 
with  another  of  the  same  kind,  the  first 
is  called  the  antecedent,  and  the  second 
the  consequent. 

2.  One  magnitude  is  said  to  be  a  mul- 
tiple of  another,  when  it  contains  that 
other  a  certain  number  of  times  exactly  : 
and  the  other  magnitude,  which  is  con- 
tained in  the  first  a  certain  number  of 
times  exactly,  is  said  to  be  a  submultiple, 
or  measure,  or  part  of  the  first.  Hence, 
also,  one  magnitude  is  said  to  measure 
another,  when  it  is  contained  in  the  other 
a  certain  number  of  times  exactly. 

3.  Two  magnitudes  are  said  to  be  equi- 
multiples of  two  others,  when  they  con- 
tain those  others  the  same  number  of 
times  exactly :  and  the  other  magnitudes, 
which  are  contained  in  the  first  the  same 
number  of  times  exactly,  are  said  to  be 
like  parts  of  the  first  two.  Thus,  7  A, 
7  B,  are  equimultiples  of  A,  B;  and 
A,  B,  are  like  parts  of  7  A,  7  B. 

4.  Two  magnitudes  are  said  to  be  com- 

207 


mensurable  with  one  another,  when  a 
common  measure  of  the  two  may  be 
found,  that  is,  a  magnitude  which  is  con- 
tained in  each  of  them  a  certain  number 
of  times  exactly.  In  like  manner,  any 
number  of  magnitudes  are  said  to  be 
commensurable,  when  there  is  some  mag- 
nitude which  is  contained  in  each  of 
them  a  certain  number  of  times  exactly. 
Magnitudes  which  have  no  common 
measure  are  said  to  be  incommensurable. 

MA'GNITUDE,  APPARENT.  The 
name  given  to  the  angle  under  which  an 
object  appears  at  the  eye,  or  the  angle 
formed  by  lines  drawn  from  the  extrem- 
ities of  the  object  to  the  eye.  The  idea 
which  we  form  of  the  real  magnitude  is 
not  that  which  is  necessarily  conveyed 
with  the  first  gift  of  sight,  but  is  gra- 
dually made  out  by  the  help  of  expe- 
rience. The  sun  and  moon  are  nearly  of 
the  same  apparent  size. 

MA'GNITUDE  OF  STARS.  The 
magnitudes  of  stars  are  vaguely  derived 
from  their  apparent  brilliancies.  Very 
brilliant  stars,  though  of  varying  bril- 
liancy, are  said  to  be  of  the  first  magni- 
tude ;  stars  of  the  next  degree  of  bril- 
liancy are  said  to  be  of  the  second  magni- 
tude; and  so  on.  Yet  there  is  little 
perceptible  difference  between  the  boun- 
dary stars  of  any  two  adjoining  classes, 
and  hence  there  is  no  little  confusion. 

MA'IIDiE  or  MA'INS.  A  tribe  of 
brachyurous  crustaceans,  or  Crabs,  named, 
from  the  genus  maia,  or  sea-spider,  as  it 
is  commonly  called. 

MAJOR  and  MTNOR.  These  terms 
are  applied,  in  Music,  to  imperfect  con- 
cords, which  differ  from  each  other  by  a 
semitone. 

MAJOR  TERM.  In  Logic,  the  Major 
Term  of  a  syllogism  is  the  predicate  of 
the  conclusion.  The  Major  Premiss  is 
the  one  which  contains  the  major  term. 
In  hypothetical  syllogisms,  the  hypotheti- 
cal premiss  is  called  the  major.  # 

MA'LACHITE.  Green  bice.  A  car- 
bonate of  copper;  a  green  carbonate, 
occurring  with  a  fibrous  structure  and 
velvety  appearance,  and  with  a  compact 
structure  in  the  mines  of  the  Uralian 
mountains. 

MA'LACOLITE.  Sahlite.  A  pyrox- 
enic  mineral,  consisting  of  a  silicate  of 
magnesia  and  lime,  found  in  Shetland, 
&c.  It  is  a  sub-species  of  oblique-edged 
augite. 

MALACO'LOGY  (Ma\aic6?,  soft,  X67op, 
a  description).  The  science  of  the  Mol- 
lusca,  termed  by  Aristotle  malakia,  com- 


MAL 


MAM 


prehending  the  examination  both  of  the 
animal  and  of  the  shell.  It  differs  from 
Conchology,  which  is  limited  to  the  ar- 
rangement of  the  shells,  and,  in  this 
respect,  cannot  claim  a  place  amongst 
the  sciences. 

MALACO'PTERY'GII  (ixaXands,  soft, 
iTTepvyiov,  a  fin).  An  order  of  Osseous 
Fishes,  in  which  the  fins  are  all  soft  or 
jointed.  The  order  is  subdivided,  ac- 
cording to  the  position  or  absence  of  the 
ventral  fin,  into — 

1.  M.  abdominales,  in  which  the  ven- 
tral fins  are  attached  to  the  abdomen 
behind  the  pectorals.  These  include  the 
greater  part  of  the  fresh-water  fishes. 

2.  M.  sub-brachiati,  in  which  the  ven- 
tral fins  are  brought  forward  under  the 
pectorals,  and  the  fishes,  which  are  chiefly 
marine,  enjoy  a  considerable  power  of 
ascending  and  descending  in  the  water. 

3.  M.  apoda,  in  which  the  ventral  fins 
are  always  wanting,  and  not  unfrequently 
the  pectoral  also. 

MALACO'STRACA  {naXanos,  soft,  '6a- 
rpanov,  a  shell).  A  sub-class  of  the  Crusta- 
cea, in  which  the  animals  have  seven  tho- 
racic and  seven  abdominal  segments.  The 
term  was  given  by  Aristotle  to  the  modern 
Crustacea,  because  their  shells  were  softer 
than  those  of  the  Mollusca,  or  ordinary 
shell-fish.  The  Malacostraca  are  divided 
into  two  groups,  according  to  the  attach- 
ment of  the  eyes  :  those  with  immoveable 
sessile  eyes  form  the  Edriophthalma ; 
those  with  moveable  pedunculated  eyes, 
the  Podophthalma. 

MALACTI'NIA  (/xaXaKot,  soft).  The 
third  class  of  the  Radiata,  consisting  of 
soft  aquatic  animals,  emitting  an  acid 
secretion  from  their  surface,  which  is 
capable  of  irritating  and  inflaming  the 
human  skin,  like  the  stinging  of  a  nettle ; 
hence  the  name  acalephce,  or  nettles,  has 
been  commonly  given  to  this  class.  They 
are  divided,  according  to  their  modes  of 
locomotion,  into  the  following  orders  : — 

1.  Ciliograda,  or  those  which  move  by 
vibratile  cilia,  as  beroe. 

2.  Physograda,  which  float  by  means 
of  air-sacks,  as  physalia. 

3.  Palliograda,  which  move  by  the 
muscular  contractions  of  a  superior  dis- 
coid mantle,  as  rhizostoma  Cuvieri. — 
Grant. 

MALAY  RACE.  One  of  the  five 
principal  divisions  of  mankind,  in  which 
the  summit  of  the  head  is  slightly  nar- 
rowed, the  forehead  a  little  arched,  the 
upper  jaw  somewhat  projecting,  the  face 
less  narrow,  and  the  features  more  pro- 
208 


minent  and  better  marked  than  in  the 
negro.  This  race  includes  the  inhabi- 
tants of  the  South  Sea  Islands. 

MALIC  ACID  {^a\ov,  an  apple).  An 
acid  existing  in  apples,  but  generally 
prepared  from  the  berries  of  the  sorbus 
aucuparia,  or  mountain  ash.  It  forms 
salts  with  alkaline  and  magnesian  bases, 
called  malates. 

MALLEABI'LITY  {malleus,  a  ham- 
mer). A  property  of  some  metals,  by 
which  they  are  capable  of  being  beaten 
out  into  plates,  or  leaves,  by  the  hammer, 
as  in  the  case  of  gold-leaf.  This  pro- 
perty depends  upon  a  high  degree  of 
tenacity,  connected  with  a  certain  degree 
of  softness. 

MA'LLEID^l.  A  family  of  mono- 
myarian  conchifers,  in  the  system  of 
Lamarck,  named  from  the  genus  malleus, 
and  belonging  to  the  ostracea  of  Cuvier, 
the  oxygones  of  Latreille. 

MALLEOLUS.  This  term  is  Latin 
for  a  hammer,  and  is  applied,  in  the  bo- 
tanical process  of  layering,  to  the  layer 
which  is  separated  from  the  parent  plant, 
from  its  lower  end  resembling  a  hammer- 
head, of  which  the  new  plant  represents 
the  handle. 

MALTHA.  Sea-wax.  A  solid,  whitish, 
bituminous  substance,  not  unlike  tallow, 
found  in  Siberia  and  Persia.  It  is,  pro- 
bably, the  bitumen  candidum  of  Pliny. 

MALTING.  The  process  of  making 
malt ;  it  consists  in  the  inducing  of  an 
artificial  growth  or  germination  of  barley, 
by  steeping  in  water,  and  then  evolving 
the  saccharine  principle  by  the  applica- 
tion of  heat. 

MALVACEAE.  The  Mallow  tribe  of  di- 
cotyledonous plants.  Herbaceous  plants, 
trees,  or  shrubs,  with  leaves  alternate; 
flowers  polypetalous  /  stamens  hypogy- 
nous,  monadelphous ;  fruit  capsular  or 
baccate,  containing  seed  with  crumpled 
cotyledons. 

MAMMA'LIA  {mamma,  a  teat).  The 
fifth  class  of  Vertebrate  animals,  which 
are  provided  with  mammary  glands  for 
the  lactation  of  their  young.  To  this  it 
may  be  added,  that  the  visceral  cavity  is 
separated  into  a  thorax  and  an  abdomen 
by  a  muscular  diaphragm,  and  that  all 
the  animals  of  the  class  breathe  by  means 
of  lungs  precisely  similar  to  our  own. 
See  Zoology. 

MAMMA/LOGY.  An  unclassical  term, 
denoting  the  science  of  mammals,  or 
animals  furnished  with  mammae,  includ- 
ing man,  the  quadrupeds,  the  quadru- 
manous  animals,  and  the  whales.    The 


MAM 


MAN 


terms  mastology  and  mastozoology  have 
been  suggested,  as  being  entirely  of  Greek 
derivation.    See  Mammalia. 

MA'MMIFERS  (mamma,  a  breast, 
fero,  to  bear).  Mammal.  A  term  applied 
to  animals  which  give  suck  to  their 
young,  including  all  the  warm-blooded 
quadrupeds  and  the  cetaceous  animals. 

MA'MMILLARY  (mammilla,  a  little 
breast).  A  term  applied  to  a  surface 
which  is  studded  over  with  prominences 
which  are  smooth,  thick,  and  rounded, 
like  a  teat. 

MA'MMOTH.  A  word  of  Tartar  ori- 
gin, denoting  an  extinct  species  of  the 
elephant  (Elephas  primigenius),  of  which 
the  fossil  bones  occur  in  various  coun- 
tries. The  term  is  applied  in  Siberia  to 
animals  which  burrow  under  ground. 

MAN.  Under  the  several  articles, 
American,  Caucasian,  Ethiopian,  Malay, 
and  Mongolian  Race,  the  characters  of 
these  varieties  of  man  are  briefly  re- 
corded. Dr.  Prichard  refers  the  differ- 
ences of  complexion  in  man  to  three 
principal  varieties,  viz. : — 

1.  The  Melanocomous,  or  black-haired, 
which  is  the  complexion  generally  preva- 
lent, except  in  the  northern  parts  of 
Europe  and  Asia.  The  colour  of  the 
skin  varies  in  intensity  from  the  black  of 
the  African  negro  to  the  light  olive  of  the 
northern  Hindoo,  thence  to  every  degree 
of  shade  in  the  Persian  and  other  Asia- 
tics, to  that  of  the  swarthy  Spaniard  and 
of  black-haired  Europeans  in  general. 

2.  The  Leucous,  albino,  or  white- 
haired,  occurring  in  all  countries,  per- 
haps most  frequently  in  hot  climates. 
They  are  characterized  by  the  entire  ab- 
sence of  colouring  matter  from  the  skin, 
hair,  and  eyes ;  the  skin  is  consequently 
milk-white  or  of  a  pinkish  hue,  the  hair 
silky-white  or  at  most  yellowish,  the  iris 
rosy,  and  the  pupil  intensely  red. 

3.  The  Xanthous,  or  yellow-haired,  in- 
cluding the  light-brown,  auburn,  yellow, 
and  red  varieties.  The  complexion  is 
fair,  becoming  more  or  less  red  on  expo- 
sure to  heat  and  light.  The  eyes  are 
light-coloured.  This  variety  predomi- 
nates in  the  temperately  cold  regions  of 
Europe  and  Asia.  <r 

MA'NAKINS.  A  group  of  small  birds, 
remarkable,  for  their  rich  plumage.  Mr. 
Swainson  makes  them  a  sub-family  of 
the  Ampelidae,  under  the  name  of 
Piprince. 

MA'NATIDjE  (manatus,  the  sea-cow, 
or  lamantine).  A  small  family  of  aquatic 
herbivorous  animals,  placed  by  Cuvier 
209 


among  the  Cetacea.  By  others  they  are 
considered  to  differ  from  the  whales,  and 
to  resemble  the  hippopotamus,  suffi- 
ciently to  be  placed  among  the  Pachyder- 
matous animals. 

MANDIBULA'TA  (mandibulum,  a 
mandible  or  jaw).  Mandibulate  Insects  ; 
a  group  in  which  the  mouth  is  furnished 
with  mandibles  or  jaws,  adapted  for 
biting  and  bruising.  This  division  in- 
cludes the  coleopterous,  orthopterous, 
neuropterous,  and  hymenopterous  in- 
sects.    See  Haustellata. 

MA'NGANESE.  A  metal  similar  to 
iron,  brittle,  and  with  difficulty  fused, 
occurring  in  the  state  of  oxide  in  some 
rocks,  to  which  it  generally  gives  a  pur- 
plish-red colour.  The  binoxide,  used  in 
chemistry,  is  commonly  termed  native 
black,  or  peroxide  of  manganese. 

MANGANESE  BLENDE.  Kobellite. 
An  ore  of  manganese,  in  which  sulphur 
occurs  in  combination  with  the  metal, 
found  at  Nagyag  in  Transylvania  and  in 
Mexico. 

MA'NGANIC  ACID.  An  acid  con- 
sisting of  one  atom  of  manganese  and 
three  of  oxygen.  It  has  not  hitherto 
been  obtained  in  a  separate  state,  but 
exists  in  the  manganate  of  potash,  com- 
monly called  mineral  chameleon. 

MA'NGANITE.  An  ore  of  manga- 
nese, consisting  of  two  prime  proportions 
of  the  deutoxide  of  the  metal,  combined 
with  one  of  water. 

MANHEIM  GOLD.  A  species  of 
brass,  consisting  of  three  parts  of  copper 
and  one  part  of  zinc. 

MANIPULATION  (manipulus,  a 
handful).  In  chemistry  and  experi- 
mental philosophy,  this  term  denotes  the 
application  of  skill  in  conducting  the 
various  operations  of  the  laboratory. 

MANO'METER  (navot,  rare,  fxerpov, 
a  measure).  Manoscope.  A  steam-baro- 
meter, employed  chiefly  for  measuring 
the  force  of  the  steam  in  boilers.  The 
term  is  also  applied  to  an  instrument  for 
testing  the  rarity  of  the  air.  See  Dasymeter. 

MA'NTIDjE.  A  family  of  orthopte- 
rous insects,  named  from  the  genus 
mantis,  and  remarkable  for  their  gro- 
tesque forms,  closely  resembling  that  of 
a  plant.  The  mantis  religiosa,  or  praying 
insect,  has  received  its  name  from  the 
peculiar  position  of  the  anterior  pair  of 
legs,  like  the  hands  of  a  person  at  prayer. 

MANTLE.  The  external  soft  con- 
tractile skin  of  the  Mollusca,  which 
covers  the  viscera  and  a  great  part  of  the 
body,  like  a  cloak. 


MAN 


MAR 


MANU'RES.  Animal,  vegetable,  or 
mineral  matters,  deposited  in  the  soil,  to 
accelerate  vegetation  and  increase  the 
production  of  crops. 

MAP  (mappa,  a  napkin).  A  repre- 
sentation, upon  a  plane,  of  some  portion 
of  the  surface  of  a  sphere,  on  which  are 
traced  the  particulars  intended  to  be  ex- 
pressed, whether  they  be  continuous  out- 
lines or  points.  The  projections  chiefly 
used  in  maps  are  the  orthographic,  the 
stereographic,  and  Mercator's.  See  Pro- 
jection. 

MARBLE.  A  term  applied  to  every 
limestone  which  is  finely  coloured  and 
capable  of  receiving  a  high  polish,  or  of 
being  worked  into  statuary;  the  pure 
white  crystalline  kinds  being  those  em- 
ployed for  the  latter  purpose.  Forest 
marble  is  a  coarse  laminated  shelly  oolite, 
interposed  between  beds  of  clay,  sand, 
and  grit. 

MARCEL'S  BLOWPIPE.  An  appa- 
ratus for  increasing  temperature,  by  urg- 
ing the  flame  of  an  alcohol  lamp  by  a 
blowpipe  supplied  with  oxygen  gas. 

MA'RGARIC  ACID  (napyaplt,  a 
pearl).  An  acid  obtained  from  human 
fat  and  vegetable  fixed  oils,  and  also 
produced  by  the  dry  distillation  of  ox 
and  mutton  suet,  and  of  stearic  acid.  Its 
name  is  derived  from  its  pearly  lustre. 

MA'RGARIN.  Margarate  of  glyceryl ; 
a  peculiar  fatty  matter  contained  in  vege- 
table oils  and  animal  fats. 

MA'RGARITE.  A  greyish-white  mine- 
ral, resembling  silvery  mica. 

MARGARFTIC  ACID.  One  of  the 
fatty  acids  produced  by  the  saponifica- 
tion of  castor  oil.  The  other  acids  ob- 
tained by  this  process  are  the  ricinic  and 
the  eloeodic. 

MA'RGARONE.  A  solid  white  fatty 
matter,  crystallizing  in  pearly  scales,  ob 
tained  by  dry  distillation  of  margaric 
acid. 

MARGINELLI'NjE.  Date-shells;  an 
aberrant  sub-family  of  the  Volutidce,  or 
volutes,  named  from  the  typical  genus 
marginella,  having  plaits  upon  the  pillar, 
and  crenated  teeth  on  the  thickened 
outer  lip;  the  foot  very  large,  but  the 
mantle  not  lobed  nor  reflected. 

MARINE  ACID.  Spirit  of  salt.  Mu- 
riatic or  hydrochloric  acid,  procured  from 
common  salt  by  distilling  it  with  sul- 
phuric acid  and  water  over  a  water-bath 

MARINE  CONGLOMERATES.    De 

posits  formed  by  sand  thrown  by  the  sea 

upon  its  shores,  mixed  with  remains  of 

shells  and  corals,  which  are  agglutinated 

210 


by  a  calcareous  cement,  finally  acquiring 
a  tolerably  firm  consistence.  Rocks  of 
this  kind  are  daily  forming  on  the  shores 
of  Sicily,  and  are  very  abundant  in  the 
West  Indies. 

MARINER'S  COMPASS.  An  instru- 
ment consisting  of  a  small  magnetic  bar, 
called  a  needle,  poised  on  its  centre  of 
gravity,  so  as  to  be  enabled  to  turn 
readily  every  way  in  ahorizontal  direction. 
After  a  few  vibrating  motions,  during 
which  it  is  said  to  traverse,  the  needle 
takes  its  direction  nearly  north  and  south, 
which  direction  is  said  to  be  in  the  plane 
of  the  magnetic  meridian  of  the  place 
where  the  compass  happens  to  be. 

Compass  variation.  A  term  expressive 
of  the  angle,  which  the  magnetic  meri- 
dian is  east  or  west  from  the  geogra- 
phical, or  true  north  and  south.  It  varies 
in  different  places  and  at  different  times. 
MARIOTTE'S  LAW.  Boyle  and  Ma- 
riotte  experimentally  investigated  the 
ratio  subsisting  between  the  density  of 
the  air,  its  elasticity,  and  the  space  it 
occupies,  when  the  following  law  was 
detected  : — that  the  density  and  elasticity 
of  atmospheric  air  are  directly,  but  the 
space  it  occupies  is  inversely,  as  the  force 
of  compression. 

MA'RKAB.  A  star  of  the  second 
magnitude  in  the  northern  constellation 
Pegasus. 

MARL.  An  argillaceous  rock,  con- 
sisting of  clay  mixed  with  lime ;  soft, 
friable,  but  not  forming  a  tenacious  paste 
with  water;  it  is  grey,  yellow,  green, 
blue,  or  red.  The  variegated  marls,  or 
keuper,  are  red,  greenish-grey,  and 
bluish,  and  contain  subordinate  beds  of 
sandstone  and  dolomite,  deposits  of 
brown  coal,  masses  of  gypsum,  and  salt. 
These  marls  are  covered  with  a  white 
quartz  sandstone,  which  connects  them 
with  the  lias. 

MARLSTONE.  A  constituent  of  the 
lias  formation,  consisting  of  arenaceous 
and  calcareous  layers,  with  nodules  of 
ironstone.  This  rock  is  well  developed 
in  Yorkshire  and  Leicestershire. 

MA'RMOLITE.  A  variety  of  serpen- 
tine, found  at  Hoboken,  in  New  Jersey. 

MARS.  •  The  planet  which  imme- 
diately follows  our  earth  in  respect  of 
distance  from  the  sun,  from  which  he  is 
separated  by  146  millions  of  miles.  His 
diameter  appears  to  be  sometimes  18", 
sometimes  19".  He  revolves  on  his  axis 
in  24h,  31'  22",  and  completes  his  orbit 
round  the  sun  in  686d,  23h,  30'  41",  4. 
MARSH'S  APPARATUS.    An  appa- 


MAR 


MEA 


ratus  for  detecting  the  presence  of  arseni- 
ous  acid  in  solution. 

MARSUPIA'TA  {marsupium,  a  pouch). 
Marsupial  animals;  an  order  of  Mam- 
malia, having  a  sack  or  pouch  under  the 
belly  in  which  they  carry  their  young,  as 
the  kangaroo  and  opossum.  They  are 
ovo-viviparous  animals,  being  interme- 
diate between  the  truly  viviparous  mam- 
malia, and  the  oviparous  birds  and  rep- 
tiles. 

MA'RTIAL.  An  old  mythological  de- 
signation of  several  preparations  of  iron, 
from  Mars,  the  god  of  war.  Hence  we 
have  martial  ethiops,  or  the  protoxide  ; 
martial  pyrites,  or  the  sulphuret. 

MASS  (ndacronai,  to  knead  together). 
In  physics,  a  term  synonymous  with 
quantity :  thus,  the  mass  of  a  body  is  the 
quantity  of  matter  it  contains.  The  mass 
and  density  of  bodies  are  estimated  ac- 
cording to  their  various  degrees  of  poro- 
sity. The  mass  represents  the  number 
of  material  particles  in  a  body :  the 
greater  the  mass,  the  less  porous  is  the 
substance.  Density,  on  the  contrary, 
expresses  the  relation  of  the  masses 
when  the  volumes  are  equal:  i.e.  "of 
two  bodies  that  is  the  more  dense,  which 
with  equal  bulk  contains  the  greater  mass." 

MASSES,  GLOBULAR.  Nodules. 
These  terms  are  applied,  in  Geology,  to 
rocks  of  irregular  form,  varying  from  a 
foot  to  a  mile  or  more,  and  imbedded 
either  in  a  stratified  or  a  massive  rock. 
Irregular  masses  are  rocks  of  no  deter- 
minate form,  and  of  any  size,  as  granite, 
greenstone,  porphyry. 

MA'SSICOT.  Yellow  oxide,  or  pro- 
toxide of  lead.  When  partially  fused  by 
heat,  it  is  called  litharge. 

MA'STODON  (/icurrdf,  abreast,  b&ovs, 
a  tooth).  A  genus  of  fossil  extinct  qua- 
drupeds, allied  to  the  elephant,  and  so 
called  from  the  form  of  the  hind  teeth, 
or  grinders,  which  have  their  surface 
covered  with  conical  mammillary  crests. 

MATER  ACETI.  Mother  of  Vine- 
gar; a  mould- plant,  belonging  to  the 
genus  mycoderma,  which  is  developed 
in  vinegar,  and  forms  thereon  a  thick 
leather-like  coat,  similar  to  the  inflam- 
matory crust  which  covers  the  crassa- 
mentum  of  blood  drawn  from  rheumatic 
patients,    i 

MATERIALISM.  A  philosophical 
system  which  refers  all  existence,  in- 
cluding the  nature  of  the  mind  or  soul 
itself,  to  a  modification  of  matter.  By 
this  system  the  brain  is  supposed  to  se- 
crete thought,  as  the  liver  secretes  bile. 
211 


MATHEMATICS  {n<idr\™,  learning). 
The  science  which  teaches  the  properties 
of  numbers  and  of  figures.  It  is,  accord- 
ingly, divided  into  two  branches,  viz. 
arithmetic,  the  science  of  number,  and 
geometry,  the  science  of  figure. 

Mixed  Mathematics  denotes  mathema- 
tical reasoning  upon  facts  in  nature,  and 
is  so  named  in  contradistinction  to  pure 
or  abstract  mathematics,  which  is  em- 
ployed in  reasoning  on  figures  and  num- 
bers, without  reference  to  facts  in  nature. 

MATRASS.  A  cucurbit,  or  vessel  of 
glass,  porcelain,  or  metal,  usually  of  a 
globular  shape,  and  open  at  the  top,  for 
the  chemical  purposes  of  digestion,  eva- 
poration, &c.    See  Alembic. 

MATRIX.  Gangue.  The  earthy  or 
stony  matter  which  accompanies  ores,  or 
envelopes  them  in  the  earth. 

MATTER.  The  general  designation 
of  whatever  occupies  space,  and  possesses 
extension  and  impenetrability :  all  bodies 
are  matter  with  fixed  boundaries.  The 
physical  and  chemical  properties  of  matter 
have  given  rise  to  two  branches  of 
science,  viz.  physics  and  chemistry. 

MAXILLO'SA  (maxilla,  a  jaw).  A 
group  of  Crustaceous  animals,  in  which 
the  mouth  is  furnished  with  jaws,  as  dis- 
tinguished from  the  Edentata,  in  which 
the  mouth  is  prolonged  in  the  shape  of 
a  sucker.  These  two  groups  are  pre- 
cisely analogous  to  those  of  the  mandi- 
bulata  and  the  haustellata  among  insects. 

MA'XIMA  and  MI'NIMA.  These 
terms,  simply  signifying  "the  greatest" 
and  "the  least,"  are  employed,  in  ana- 
lysis, to  signify  not  the  absolute  greatest 
and  least  values  of  a  variable  quantity, 
but  the  values  it  has  when  it  ceases  to 
increase,  and  begins  to  decrease,  and  vice 
versa".  A  variable  quantity  may,  there- 
fore, have  many  maxima  and  minima,  as 
the  highest  and  lowest  points  at  which 
the  mercury  stands  in  a  barometer  at 
different  times. 

MEAN  QUANTITY.  In  Mathema- 
tics, the  mean  of  two  or  more  quantities 
is  a  quantity  of  intermediate  value,  found 
by  determinate  rules.  There  are  several 
modes  of  finding  a  mean  quantity. 
Thus :— 

1.  The  arithmetical  mean  of  several 
quantities  is  simply  the  average  found  by 
dividing  the  sum  of  all  the  quantities  by 
their  number ;  and  this  is  the  mean  al- 
ways understood,  unless  another  kind  be 
specified.  Thus,  if  three  measures  of 
the  same  length  give  122,  123,  and  123-4, 
the  average  or  arithmetical  mean  is  122*8. 


ME  A 


MEC 


2.  The  geometrical  mean  of  two  quan- 
tities is  the  square  root  of  the  product  of 
those  quantities.  In  Geometry,  the  term 
is  synonymous  with  mean  proportional, 
and  it  is  a  quantity,  such  that,  if  placed 
between  two  given  quantities,  a  series  of 
three  continued  proportionals  would  be 
formed  ;  in  other  words,  the  first  of  the 
two  given  quantities  is  to  the  mean  pro- 
portional as  this  is  to  the  other  given 
quantity. 

3.  The  harmonical  mean  is  a  number, 
such  that,  the  first  and  third  terms  being 
given,  the  first  is  to  the  third  as  the  dif- 
ference of  the  first  and  second  is  to  tbe 
difference  of  the  second  and  third,  the 
second  being  the  harmonical  mean. 

MEAN  SUN.  Solar  days  are  not 
equal  in  duration ;  a  clock  regulated  by 
the  sun  would,  consequently,  need  fre- 
quent adjustment.  To  avoid  this,  an 
imaginary  or  mean  sun  is  supposed  to 
move  regularly  round  the  equator  in  the 
same  time  as  that  in  which  the  true  sun 
moves  irregularly  round  the  ecliptic. 
Such  a  time  represents  a  mean  solar  day, 
and  it  is  the  average  of  all  the  apparent 
solar  days  in  a  year.  See  Equation  of  Time. 

1.  Mean  Noon.  This  is  an  expression 
connected  with  the  above  fiction  of  a 
mean  sun;  and  the  term  "  mean"  is  here, 
as  above,  opposed  to  "apparent"  or 
"  real."  Thus,  apparent  noon  is  the  real 
or  true  noon,  when  the  true  sun,  the  sun 
which  appears,  is  on  the  meridian ; 
whereas  mean  noon  takes  place  when  the 
mean  sun,  the  average  imaginary  sun, 
which  does  not  appear  at  all,  is  on  the 
meridian. 

2.  Mean  Moon.  The  still  greater  ab- 
sence of  uniformity  in  the  actual  motion 
of  the  moon  induced  astronomers  to  em- 
ploy an  imaginary  or  mean  moon,  in  the 
same  manner  as  the  "  mean  sun"  above 
mentioned.  This  mean  moon  is  made 
to  move  uniformly  in  the  equator,  or  in 
the  ecliptic,  as  required.  The  Kalendar 
Moon  is  another  fictitious  moon,  em- 
ployed for  regulating  the  finding  of 
Easter ;  this  moon  is  generally  a  day  or 
more  distant  from  the  mean  moon. 

3.  Mean  Time.  Equal  or  mean  time 
is  that  which  is  reckoned  by  a  clock, 
supposed  to  indicate  exactly  twenty-four 
hours,  from  twelve  o'clock  on  one  day  to 
twelve  o'clock  on  the  next  day.  Appa- 
rent or  real  time  is  that  which  is  mea- 
sured by  the  apparent  motion  of  the  sun 
in  the  heavens,  as  indicated  by  a  meri- 
dian line,  or  sun-dial. 

4.  Mean  Anomaly  of  a  Planet.     Its 

212 


angular  distance  from  the  aphelion  or 
perihelion,  supposing  the  planet  to  re- 
volve in  a  circle  with  its  mean  velocity. 

5.  Mean  Conjunction  or  Opposition. 
The  mean  place  of  the  sun  when  in  con- 
junction with,  or  opposition  to,  the  mean 
place  of  the  moon  in  the  ecliptic. 

6.  Mean  Distance  of  a  Planet  from  the 
Sun.  An  arithmetical  mean  between 
the  planet's  greatest  and  least  distances  ; 
or,  the  semi-transverse  diameter  of  its 
orbit. 

MEANS  and  EXTREMES.  In  any 
proportion  the  first  and  fourth  terms  are 
called  the  extremes,  the  second  and  third 
the  means,  and  the  product  of  the  former 
is  equal  to  the  product  of  the  latter.  Thus, 
in  the  proportion  15  .'20  ; '.  21  ;  28, 
since  the  two  ratios  are  equal,  we  have 

15  _  21 

20  ~  28  J 
and,  if  we  multiply  each  of  these  equals 
by  20  x  28,  we  have   15  x  28  =  20  x  21, 
or   the    1st  x  4th  =  2nd  x  3rd.      See 
Proportion. 

MEASURE  OF  A  NUMBER.  One 
number  is  said  to  be  a  measure  or  a  factor 
of  another,  when  it  divides  it  exactly, 
without  a  remainder.  Thus,  1,  2,  3,  4, 
6,  12,  are  all  measures  or  factors  of  12. 
Unity,  however,  is  not  generally  named 
among  the  divisors  of  a  number. 

1.  Greatest  Common  Measure.  Any 
number  which  divides  without  remainder 
each  of  two  or  more  numbers,  is  said  to 
be  a  common  measure  or  common  factor 
of  those  numbers ;  and,  of  course,  the 
greatest  number  which  so  divides  them 
is  their  greatest  common  measure.  Thus, 
3,  5,  15,  are  each  of  them  common  mea- 
sures of  30  and  of  45,  and  15  is  their 
greatest  common  measure. 

2.  Measure,  in  Geometry.  A  magnitude 
or  quantity  assumed  as  a  unit,  and  em- 
ployed to  express  the  relations  of  other 
magnitudes  or  quantities  of  the  same 
kind.  Euclid  defines  the  measure  of  a 
quantity  to  be  that  which,  being  repeated 
a  certain  number  of  times,  becomes  equal 
to  the  quantity  measured. 

MEASURES  (in  Geology).  A  term 
sometimes  employed  as  synonymous  with 
beds  or  strata. 

MECHANICAL  CURVE.  This  is  now 
called  the  transcendental  curve.  It  is  a 
curve  in  which  the  relation  between  the 
abscissa  and  the  ordinate  cannot  be  ex- 
pressed by  an  algebraic  equation. 

MECHANICAL  ORIGIN,  ROCKS 
OF.  A  term  applied  to  rocks  composed 
of  sand,  pebbles,  or  fragments,  to  distin- 


MEC 


MEG 


guish  them  from  those  of  a  uniform  crys- 
talline texture,  which  are  of  chemical 
origin. 

MECHANICAL  PHILOSOPHY.  The 
application  of  mechanics  to  physical 
science.  Hence  the  term  Mechanists 
was  applied  to  those  philosophers  who 
referred  all  the  phenomena  of  the  uni- 
verse to  the  agency  of  mechanical  forces, 
in  opposition  to  the  Dynamical  school, 
which  insists  on  a  living  principle  in 
nature,  antecedent  to,  and  distinct  from, 
the  visible  phenomena  of  nature. 

MECHANICAL  POWERS.  The  gene- 
ral designation  of  six  simple  machines, 
viz.,  the  lever,  the  pulley,  the  wheel  and 
axle,  the  inclined  plane,  the  wedge,  and 
the  screw.  All  the  different  compound 
engines,  however  mixed  or  complex 
their  construction,  consist  only  of  various 
combinations  of  these  few  individual 
powers. 

MECHANICAL  SOLUTION.  A  term 
applied  to  the  solution  of  those  geometri- 
cal problems  which  require  other  instru- 
ments (machinee)  than  those  employed  in 
the  constructions  of  pure  geometry.  The 
latter  being  effected  merely  by  straight 
lines  and  circles,  require  only  a  rule  add 
compasses. 

MECHA'NICS  {fxnxavt),  a  machine). 
The  science  which  treats  of  the  equili- 
brium and  motion  of  bodies.  That  part 
of  the  subject  which  relates  to  the  condi- 
tions of  equilibrium  is  called  statics; 
while  that  which  investigates  the  motion 
which  a  body  acquires  when  the  forces 
applied  to  it  are  not  in  equilibrium,  is 
termed  dynamics. 

MECHLO'IC  ACID.  A  compound  of 
meconia,  a  neutral  principle  existing  in 
opium,  and  chlorine,  discovered  in  1835 
by  Couerbe. 

MECO'NIC  ACID  (n^ncav,  a  poppy). 
A  tribasic  acid,  obtained  from  poppies, 
constituting  the  characteristic  acid  of 
opium.  Its  congeners  are  the  comenic, 
which  is  bibasic ;  and  the  parameconic, 
which  is  monobasic. 

MEDIUM  {medius,  middle).  In  Phy- 
sics, the  space  or  substance  in  which 
bodies  subsist  or  move.  Newton  con- 
ceived a  universal  medium,  or  ether, 
more  subtil  than  air,  through  which  the 
heavenly  bodies  move.  This  idea  favours 
the  theory  of  the  transmission  of  light  by 
undulation. 

MEDU'LLARY  RAYS  {medulla,  pith). 
A  botanical  term  applied  to  the  thin  ver- 
tical radiating  plates  of  muriform  cellular 
tissue,  which  serve  to  connect  the  centre 
213 


of  an  exogenous  stem  with  the  circum- 
ference. They  are  technically  called  the 
silver  grain,  and  they  produce,  on  a  lon- 
gitudinal section  of  the  stem,  the  glancy 
lustre  which  so  remarkably  characterizes 
the  plane  and  the  sycamore. 

MEDU'LLARY  SHEATH  (medulla, 
pith).  The  sheath  which  immediately 
surrounds  the  medulla,  or  pith,  of  exo- 
genous plants.  It  consists  of  spiral  ves- 
sels and  woody  tissue,  and  forms  an  ex- 
ceedingly thin  layer. 

MEDU'LLIN  {medulla,  marrow).  The 
name  given  by  Dr.  John  to  the  porous 
pith  of  the  sun-flower. 

MEDUSA.  A  genus  of  the  Acalephae, 
or  Sea-nettles ;  marine  radiated  animals, 
without  shells.  The  name  is  derived 
from  their  organs  of  motion  being  spread 
out  like  the  snaky  hair  of  the  fabulous 
Medusa.  On  being  touched,  they  induce 
redness  and  a  tingling  sensation ;  they 
are  also  supposed  to  occasion,  in  certain 
latitudes,  the  phosphorescent  appearance 
of  the  sea. 

MEE'RSCHAUM.  Ecume  de  mer.  A 
silicate  of  magnesia;  a  greasy,  soapy 
substance,  occurring  in  Cornwall.  In 
Germany  and  Turkey  it  is  manufactured 
into  tobacco  pipes. 

MEGALO'PTERANS  (/ueyac,  great, 
nrepov,  a  wing).  A  family  of  Neuropte- 
rous  insects,  characterized  by  their  large 
wings  horizontally  folded. — Latreille. 

MEGALOSAU'RUS  {neydKn  cavpa, 
great  lizard).  A  fossil  gigantic  amphi- 
bious animal  of  the  saurian,  or  lizard  and 
crocodile  tribe,  found  in  the  oolitic  slate 
at  Stonesfield,  near  Woodstock,  and  other 
localities. 

MEGANY'CTERANS  (yueyav,  large, 
vvKrepis,  a  bat).  A  tribe  of  Cheiropterous 
animals,  including  the  largest  species  of 
bats,  or  "  flying  foxes." 

MEGAPODI'IDjE.  The  name  given 
by  Mr.  Swainson  to  a  family  of  the  Ra- 
sores,  from  the  genus  megapodius,  which, 
with  the  allied  genera,  is  referred  by 
other  naturalists  to  the  Cracidae,  or 
Curassows. 

ME'GASCOPE  (fxeya9,  large,  ovcoTreo), 
to  examine).  An  optical  instrument, 
constructed  on  the  principle  of  the  solar 
microscope,  for  examining  bodies  of  large 
dimensions. 

MEGATHE'RIUM  (Me7a  6npiov,  great 
beast).  A  fossil  extinct  quadruped,  re- 
sembling a  gigantic  sloth,  and  character- 
istic of  the  later  tertiary  period  on  the 
continent  of  South  America.  This,  and 
some  other  genera  of  extinct  Edentata, 


MEI 


MEN 


constitute  the  Megatheriidce,   or  mega- 
theroids  of  Owen. 

MEI'ONITE.  Prismato-pyramidal  fel- 
spar, occurring  together  with  ceylanite 
and  nepheline,  in  granular  limestone,  at 
Monte  Somraa,  near  Naples.  This,  and 
some  other  felspathic  substances  are  now 
united  under  the  general  term  wernerite. 
MELAIN  (/xeAa?,  black).  The  colour- 
ing matter  of  the  ink  of  the  cuttle-fish. 

MELAM.  A  substance  formed  by 
distilling  dry  hydro-sulpho-cyanate  of 
ammonia.  On  boiling  melam  with  hy- 
dro-chloric acid,  a  crystalline  substance 
is  generated,  called  melamine. 

MELANIA'N^E.  Black  snails  ;  a  sub- 
family of  the  Turbidts,  named  from  the 
genus  melania,  and  having  a  spiral  shell, 
the  spire  being  generally  longer  than  the 
aperture,  the  body-whorl  small. 

ME'LANIC  (M<?\ar,  black).  A  term 
applied  by  Dr.  Prichard  to  one  of  the 
three  varieties  of  mankind,  derived  from 
the  colour  of  the  hair,  and  including  all 
individuals  or  races  which  have  black 
hair.     See  Man. 

ME'LANITE.  A  black  variety  of 
garnet,  found  in  the  neighbourhood  of 
Frascati,  near  Rome,  and  in  the  basalt  of 
Bohemia. 

MELA'NTERITE.  A  mineralogical 
name  for  green  vitriol,  or  native  sulphate 
of  iron. 

MELANTHA'CEjE.  The  Colchicum 
tribe  of  monocotyledonous  plants.  Herbs 
with  a  rhizome,  sometimes  fleshy ;  leaves 
sheathing  at  the  base ;  flowers  hexapetal- 
oideous,  tubular ;  stamens  6  ;  ovarium 
3-celled ;  seeds  albuminous. 

MELASO'MA  (/ueXa?,  black,  awfxa,  the 
body).  A  family  of  the  heteromerous 
Coleoptera,  characterized  by  the  black  or 
ashy-brown  colour  of  the  body.  The 
wings  are  usually  absent,  and  the  elytra, 
or  wing  cases,  united. 

MELA'SSES  (M<?\<,  honey).  The  un- 
crystallizable  part  of  the  juice  of  the 
sugar-cane,  separated  from  the  sugar 
during  its  manufacture. 

MELA'SSIC  ACID  (Me\c,  honey).  An 
acid  produced  by  the  simultaneous  action 
of  alkalies  and  heat  upon  grape  sugar. 

MELASTOMA'CEjE  ((xeXav,  black, 
trrojua,  mouth ;  from  the  fruit  of  some  of 
the  species  staining  the  lips  black).  A 
family  of  dicotyledonous  plants,  charac- 
terized by  their  opposite  leaves,  with 
several  large  veins  running  from  the  base 
to  the  apex,  resembling  those  of  mono- 
cotyledonous plants ;  and  the  long-beaked 
anthers. 
214 


MELIA'CEiE.  The  Bead-tree  tribe  of 
dicotyledonous  plants.  Trees  or  shrubs 
with  leaves  alternate ;  flowers  symmetri- 
cal ;  calyx  imbricated ;  stamens  hypogy- 
nous ;  ovarium  of  several  cells ;  seeds 
definite,  apterous. 

ME'LILITE.  A  species  of  garnet, 
found  at  Capo  di  Bove,  near  Rome. 

MELIPHA'GID^  (M<?\<,  honey,  <pd^o, 
to  eat).  The  Honey-suckers ;  a  family 
of  the  Insessores  or  Perching  birds,  dis- 
tinguished from  all  the  allied  families  by 
their  notched  bill.  They  are  chiefly  con- 
fined to  Australia.  (See  Tenuirostres.) 
According  to  Macgillivray,  these  birds 
constitute  a  family  of  the  Repfatrices,  or 
Creepers,  characterized  by  having  the 
three  fore  toes  more  or  less  united  at  the 
base,  and  spreading  little. 

ME'LLITATES.  Salts  formed  by  the 
combination  of  mellitic  acid  with  a  sali- 
fiable base. 

ME'LLITE.  Honey-stone.  Mellitate  of 
alumina ;  a  salt  found  in  beds  of  brown 
coal  at  Artern  in  Thuringia. 

ME'LLITIC  ACID  {fieXi,  honey).  An 
acid  discovered  in  mellite,  or  honey- 
stone,  a  rare  mineral,  consisting  of  the 
mellitate  of  ammonia. 

ME'LLON.  A  lemon-yellow  substance 
consisting  of  azote  and  carbon,  considered 
as  a  compound  radical. 

ME'LODY  (iueAydm,  a  singing).  The 
combination  of  harmonious  sounds  is  a 
chord;  an  agreeable  succession  of  notes 
is  a  melody ;  and  a  succession  of  chords 
constitutes  harmony. 

MELOLO'NTHIDjE.  A  family  of 
Coleopterous  insects,  of  the  section  la- 
mellicornes,  named  from  the  melolontha 
vulgaris,  or  common  cockchafer. 

MELONI'DIUM  (/^Xox,  an  apple). 
The  name  given  by  Richard  to  an  in- 
ferior compound  fruit  with  a  fleshy  peri- 
carp—the pomum  of  other  writers. 

MELTING  POINT.  That  point  of 
the  thermometer  which  indicates  the 
temperature  at  which  a  solid  becomes 
fluid.  Thus,  ice  melts  at  32°  Fahr.,  sul- 
phur at  218°,  gold  at  5237°. 

ME'NACHANITE.  An  oxide  of  tita- 
nium, found,  accompanied  with  fine 
quartz  sand,  in  the  bed  of  a  rivulet 
which  enters  the  valley  of  Menaccan  in 
Cornwall. 

ME'NILITE.  A  sub-species  of  indi- 
visible quartz ;  an  opaline  substance, 
called  also  liver  opal,  from  its  brown 
colour,  found  at  Menil-Montant,  near 
Paris,  in  a  bed  of  adhesive  slate.  An- 
other kind,  called  grey  menilite,  occurs  at 


MEN 


MER 


Argenteuil,  near  Paris,  imbedded  in  a 
clayey  marl. 

MENFSCUS  (ju>;>n,  the  moon).  A  lens 
which  is  concave  on  one  side  and  convex 
on  the  other,  its  section  resembling  the 
appearance  of  the  new  moon. 

MENISPERMA'CE^  (/up*,  the  moon, 
anepfia,  seed ;  so  named  from  the  cres- 
cent-like form  of  the  fruit  of  the  typical 
genus  menispermum).  The  Cocculus  tribe 
of  Dicotyledonous  plants.  Leaves  alter- 
nate ;  flowers  polypetalous,  unisexual ; 
stamens  hypogynous;  fruit  a  1-seeded 
drupe. 

MENISPE'RMIC  ACID.  An  acid 
obtained  from  the  berries  of  the  meni- 
spermum cocculus,  where  it  exists  in 
combination    with    the    alkaloid    picro- 

MENKAR,  or  a  CETUS.  A  star  of 
the  second  magnitude  in  the  head  of  the 
southern  constellation  Cetus. 

ME'NSTRUAL  EQUATION.  The 
name  given  to  an  apparent  monthly  dis- 
placement of  the  sun  in  longitude,  of  a 
parallactic  kind,  owing  to  the  real  nature 
of  the  curve  described  by  the  earth's 
centre,  which  is  not  an  exact  ellipse,  but 
an  undulated  curve.  The  actual  devia- 
tion or  excursion  of  the  earth  from  the 
i  ellipse  is,  however,  very  small,  the  great- 
est amount  of  the  menstrual  equation 
being  less  than  the  sun's  horizontal 
j    parallax,  or  than  8  6". 

ME'NSTRUUM.  A  chemical  term 
synonymous  with  solvent,  and  denoting 
a  liquid  which  does  not  change  the  na- 
ture of  the  substance  to  be  dissolved. 
Thus,  pure  water  is  employed  to  dissolve 
gum,  alcohol  to  dissolve  resins,  acids  to 
dissolve  the  bases  of  colchicum  and 
squill. 

MENSURATION.  The  operation  of 
measuring;  a  term  generally  denoting 
the  application  of  arithmetic  to  geometry, 
and  the  methods  of  finding  the  dimen- 
sions and  areas  of  figures,  the  contents 
of  solids,.  &c. 

MEPH.FTIC  ACID.  A  designation 
of  carbonic  acid  gas,  derived  from  Me- 
phitis, the  fabled  Roman  goddess  of  im- 
pure exhalations.  Mephitic  air  is  another 
name  for  nitrogen  gas. 

MERCA'PTAN.  A  compound  of  hy- 
drogen, carbon,  and  sulphur,  named  from 
its  energetic  action  on  binoxide  of  mer- 
cury— quasi  mercurium  captans.  It  is 
alcohol,  of  which  the  oxygen  is  replaced 
by  sulphur. 

MERCA'TOR'S  CHART.  An  artifi- 
cial mode  of  representing  a  sphere  upon 
215 


a  plane,  adopted  for  nautical  charts.  See 
Projection. 

ME'RCURY.  The  nearest  planet  to 
the  sun,  from  which  it  appears  to  be  se- 
parated only  from  sixteen  to  twenty-nine 
degrees.  Its  direct  distance  from  the 
earth  is  37,143,000  miles;  its  apparent 
diameter  is  about  seven  minutes,  nearly 
two-fifths  that  of  the  earth.  It  turns  on 
its  axis  in  24h,  5'  3",  and  completes  its 
orbit  in  87d,  23h,  25'  44",  with  a  velocity 
of  111,000  miles  an  hour.  It  sometimes 
crosses  the  disc  of  the  sun,  so  as  to  ap- 
pear like  a  small  dark  spot  passing  over 
the  sun's  face ;  this  is  called  the  transit 
of  Mercury. 

ME'RCURY  (in  Chemistry).  A  metal 
which  is  always  fluid  at  a  temperature 
above  —39°.  From  its  mobility  and  its 
resemblance  to  silver,  it  is  commonly 
called  quicksilver. 

1.  Native  or  Virgin  Mercury.  The 
pure  metal,  found  in  the  form  of  globules, 
in  cavities  of  the  ores  of  this  metal. 

2.  Native  Amalgam.  An  ore  consisting 
of  mercury  combined  with  silver. 

3.  Native  Cinnabar.  Native  vermilion, 
or  the  bisulphuret  of  mercury ;  the  ore 
which  yields  the  mercury  of  commerce. 

4.  Corneous  Mercury.  Mercurial  horn 
ore,  or  the  proto-chloride  of  mercury. 

MERE'NCHYMA  (MePof,  a  part,  ??- 
Xvna,  an  infusion).  Sphcerenchyma.  A 
term  applied  by  Morren  to  the  spherical 
variety  of  the  parenchyma  of  plants. 

MERGANI'NiE.  Mergince.  A  sub- 
family of  the  Anatidae,  consisting  of  the 
genus  mergus,  the  goosander  or  mer- 
ganser of  the  British. 

ME'RICARP  (/u<?por,  a  part,  Kapwos, 
fruit).  The  botanical  designation  of  a 
half  of  the  fruit  of  Umbelliferous  plants. 
What  are  called  seeds  in  these  plants  are, 
in  fact,  fruits,  each  consisting  of  two 
achenia,  or  mericarps,  placed  face  to  face, 
and  separating  from  a  central  axis.  The 
two  together  are  called  cremocarp  {upe- 
fxdu),  to  suspend),  from  their  being 
suspended  from  the  common  central 
axis. 

MERFDIAN  (meridies,  noon  or  mid- 
day). A  geographical  term,  denoting  a 
great  circle  of  the  sphere  passing  through 
the  zenith  and  the  poles  of  the  earth. 
The  line  which  marks  the  longitude  of  a 
place  is  called  its  meridian,  because, 
when  the  sun  passes  this  circle,  it  is 
noon  in  all  the  places  situated  under  it. 
Modern  nations  generally  adopt  the 
capitals,  or  observatories,  of  their  own 
countries  as  First  Meridians;  thus  the 


MER 


MET 


English  reckon  from  London,  or  the 
Royal  Observatory  at  Greenwich,  the 
French  from  Paris,  the  Spanish  from 
Madrid,  &c.  On  the  celestial  globe  the 
meridian  is  represented  by  the  brass 
circle  perpendicular  to  the  horizon. 

1.  Meridian  Altitude.  The  altitude, 
or  height  above  the  horizon,  in  degrees, 
of  any  celestial  object,  when  it  crosses 
the  meridian  of  a  place. 

2.  Meridian,  Magnetic.  The  magnetic 
meridian,  as  pointed  out  by  the  mariner's 
ompass,  differs  from  the  geographical  (or 
real  north  and  south)  by  the  amount  of 
the  variation  of  the  compass.  In  other 
words,  if  we  conceive  a  vertical  plane  to 
be  drawn  through  the  axis  of  a  magnetic 
needle  when  in  a  state  of  rest,  we  have 
the  magnetic  meridian  for  the  particular 
place  where  the  needle  is.  See  Dip  of 
Magnetic  Needle. 

MERITHA'LLUS  (fxepo?,  a  part,  9a\- 
X6f,  a  young  shoot).  The  term  applied 
by  Du  Petit  Thouars  to  the  internodium 
of  other  writers,  denoting  that  portion  of 
the  axis  of  a  plant  which  is  between  two 
nodes. 

MERO'PIDjE  {merops,  the  bee-eater). 
The  Bee-eaters ;  a  family  of  the  Inses- 
sores,  or  Perching  birds,  belonging  to  the 
warmer  regions  of  the  Old  Continent  and 
its  islands  ;  one  species  visits  this  coun- 
try at  irregular  intervals.  See  Fissi- 
rostres. 

MERULI'DjE  (merulus,  a  thrush). 
The  Thrushes  ;  a  family  of  the  Insessores, 
or  Perching  birds,  in  which  the  point  of 
the  beak  is  not  hooked,  and  the  lateral 
tooth  is  not  so  prominent  as  in  the 
Laniadee,  or  Shrikes.     See  Dentirostres. 

MESEMBRYA'CE^E.  Ficoidecc.  The 
Fig-marigold  tribe  of  Dicotyledonous 
plants.  Succulent  shrubs  or  herbs  with 
showy  flowers ;  sepals  definite,  succu- 
lent; petals  indefinite,  linear;  stamens 
indefinite;  ovary  many-celled;  capsule 
with  a  starry  dehiscence. 

MESITE.  A  liquid  existing  in  pyro- 
xylic  spirit,  and  produced  in  the  distilla- 
tion of  wood.  Mesiten  is  a  similar  pro- 
duct of  the  same  process.  ftfysitylene  is 
a  light  oily  liquid,  procured  by  distilling 
pyro-acetic  spirit  [acetone)  with  fuming 
sulphuric  acid. 

MESO-  (jueo-oc,  middle).  The  Greek 
term  for  middle,  or  that  which  is  situate 
between  others. 

1.  Meso-carp  (/captor,  fruit).  The  in- 
termediate part  of  the  pericarp  of  fruits. 
When  fleshy,  it  is  termed  sarcocarp.  The 
fibrous  portion  of  the  fruit  of  the  cocoa 
216 


palm  is  the  mesocarp;  the  eatable  part 
of  the  cherry  or  peach  is  the  sarcocarp. 

2.  Meso-labe  (\a(3etv,  to  take).  A  ma- 
thematical instrument  used  by  Eratos- 
thenes for  finding  mean  proportional 
lines,  required  in  the  problem  for  the 
duplication  of  the  cube. 

3.  Meso-lite  {\iOos,  a  stone).  Needle- 
stone  ;  a  zeolitic  substance,  consisting  of 
a  hydrated  silicate  of  alumina,  lime,  and 
soda,  and  usually  referred  to  mesotype. 

4.  Meso  phlceum  (^Xotof ,  bark).  That 
portion  of  the  bark  of  plants  which  lies 
between  the  epiphlceum  and  the  endo- 
phlceum,  or  liber.    See  Bark. 

5.  Meso-phyllum  {(pvWov,  a  leaf).  The 
cellular  substance  of  the  leaves  of  plants, 
also  called  diachyma  and  diploe. 

6.  Meso-sperm  {cirepixa,  seed).  The 
middle  one  of  the  three  membranes  by 
which  seeds  are  sometimes  enveloped. 

7.  Meso-type  (rvwo^,  form).  A  silicate 
of  soda  and  alumina ;  a  simple  mineral, 
white,  and  needle-shaped;  one  of  the 
zeolite  family,  frequently  found  in  trap- 
rocks.  To  this  are  referred  the  natrolite 
of  Klaproth,  the  needle-stone  of  Werner, 
the  mesolite,  &c. 

META'BOLA  (nerafoXn,  change).  A 
term  applied  by  zoologists  to  those  genera 
of  insects  which  undergo  metamorphosis, 
or  pass  through  the  larva,  pupa,  and 
imago  states  of  insect  existence.  See 
Ametabola. 

METACE'NTRE  {iieta,  a  preposition 
denoting  change,  K€vrpov,  a  centre).  When 
the  position  of  equilibrium  of  a  floating 
body  has  been  disturbed,  if  the  vertical 
line  passing  through  the  centre  of  buoy- 
ancy (the  line  of  the  thrust  of  the  fluid), 
when  produced  upward,  meets  the  axis 
passing  through  the  centre  of  gravity, 
the  point  of  intersection  is  called  the 
metacentre. 

METAGA'LLIC  ACID.  A  compound 
obtained  by  the  partial  decomposition  of 
gallic  acid,  when  rapidly  heated  to  480°. 

METALLIC  DEPOSITS.  By  this 
term,  geologists  denote  metallic  matters 
with  which  the  substance  of  rocks  is  fre- 
quently permeated,  in  the  form  of  grains, 
filaments,  nodules,  irregular  plates  or 
veins,  and  strata  or  beds.  In  these  cases 
the  metallic  matters  are  supposed  to  be 
of  contemporaneous  origin  with  the  rocks 
or  formations  containing  them. 

META'LLIC  VEINS.  Metallic  ores 
and  mineral  substances  found  in  fissures 
of  rocks  which  are  composed  of  very 
different  materials.  They  occur  chiefly 
in  the  primary,  and  in  the  lower  and 


♦ 


MET 


middle,  secondary  rocks ;  they  vary  in 
width  from  an  inch,  or  less,  to  several 
yards,  and  sometimes  extend  to  many 
miles.  These  veins,  unlike  metallic  de- 
posits, were  formed  at  periods  subsequent 
to  the  formation  of  the  rocks  in  which 
they  occur. 

MET  ALLOGRAPH  Y  {^raWov,  a 
metal,  7pa0o),  to  describe).  That  branch 
of  science  which  treats  of  metals. 

ME'TALLOID  (ueTaXW,  a  metal, 
e'ldos,  likeness).  A  term  applied,  at  first, 
to  the  metals  obtained  from  the  fixed 
alkalies  and  some  of  the  earths.  The 
term  is  sometimes  applied  to  the  inflam- 
mable non-metallic  bodies,  as  sulphur, 
phosphorus,  &c. 

METALLU'RGY  (^xeraWoi/,  a  metal, 
epyov,  work).  The  separation  of  metals 
from  their  ores,  comprising  the  opera- 
tions of  assaying,  refining,  smelting,  &c. 

ME'TALS  (/ueraXAov,  a  mine ;  a  mine- 
ral; a  metal).  A  class  of  elementary 
bodies,  most  of  which  are  characterized 
by  their  peculiar  metallic  lustre,  and, 
generally  speaking,  by  their  great  specific 
gravities.  They  are  divided  into  different 
classes,  according  to  their  affinity  for  oxy- 
gen, and  the  peculiar  properties  of  their 
various  oxides.  They  are  distinguished 
as  : — 

1.  Perfect  Metals.  Those  which  com- 
bine with  difficulty  with  oxygen,  and 
consequently  are  not  easily  oxidized ;  as 
such,  they  readily  part  with  oxygen  by 
the  simple  application  of  heat,  and  are 
converted  into  pure  metals.  The  best 
known  are  platinum,  gold,  and  silver. 
Mercury  holds  an  intermediate  place  be- 
tween these  and  the  next  class. 

2.  Base  Met  tit.  Those  which  readily 
combine  with  oxygen,  partly  by  mere 
contact  with  the  atmosphere,  or  when 
heated  and  fused.  They  are  not  reducible 
by  the  application  of  heat  only,  but  re- 
quire the  admixture  of  some  substance, 
as  coal,  to  attract  the  oxygen  from  the 
oxide.  The  best  known  are  iron,  copper, 
lead,  tin,  and  zinc.  The  metals  com- 
posing this  and  the  preceding  class  are 
termed,  from  their  great  specific  gra- 
vities, the  heavy  metals. 

3.  Acidifying  Met'ds.  Those  which, 
entering  into  combination  with  oxygen, 
possess  the  property  of  acids,  which  are 
hence  called  metallic  acids.  These  metals 
are  tellurium,  arsenic,  chromium,  mo- 
lybdenum, tungsten,  columbium,  and 
selenium. 

4.  Terrigenous  Metals.  Those  whose 
oxides  yield  the  earths,  properly  so  called. 

217 


MET 

They  resist  the  action  of  heat,  and  are 
insoluble  in  water.  These  are  aluminum, 
yttrium,  cerium,  lantanum,  thorium, 
glucinum,  and  zirconium. 

5.  Katigenous  Metals.  Those  which 
oxidize  most  readily,  their  oxides  consti- 
tuting the  alkalies.  These  are  magne- 
sium, calcium,  strontium,  barium,  li- 
thium, sodium,  and  potassium.  As  the 
metals  of  this  and  of  the  preceding  class 
are  some  lighter  and  others  but  little 
heavier  than  water,  they  are  called  light 
metals. 

METAME'RIC  (jue-ra,  a  preposition 
denoting  change,  juepor,  a  part).  A  term 
applied  to  compounds  in  which  the  ulti- 
mate elements  are  the  same  as  in  other 
well-known  combinations,  but  are  con- 
sidered to  be  arranged  in  a  different  way : 
thus,  oxygen,  hydrogen,  sulphur,  and  a 
metal,  may  be  considered  as  combined  in 
the  form  of  sulphuretted  hydrogen  and  a 
metallic  oxide,  or  of  water  (consisting  of 
oxygen  and  hydrogen)  and  a  metallic 
sulphuret.     See  Isomeric  and  Polymeric. 

METAMO'RPHIC  (nera,  a  preposi- 
tion denoting  change,  m°p0»7»  form).  A 
term  applied  by  Mr.  Lyell  to  the  series 
of  crystalline  slates  which  occurs  espe- 
cially in  the  central  ridges  of  mountain 
chains.  The  term  denotes  that  their 
structure  has  been  changed,  since  the 
time  of  their  first  formation,  by  plutonic 
action.     See  Hypozoic  System. 

METAMORPHO'SIS  (vera,  a  prepo- 
sition denoting  change,  and  ixopcprj,  form). 
Literally,  a  change  of  form.  A  term  em- 
ployed by  Liebig  to  denote  that  chemical 
action  by  which  a  given  compound  is 
caused,  by  the  presence  of  a  peculiar 
substance,  to  resolve  itself  into  two  or 
more  compounds ;  as  sugar,  by  the  pre- 
sence of  yeast,  into  alcohol  and  carbonic 
acid. 

METAMORPHO'SIS  (in  Botany). 
Morphology.  These  terms  denote  a  the- 
ory, according  to  which  the  several  organs 
of  plants  are  referred  to  a  typical  organ, 
varying  in  their  modes  of  development, 
not  on  account  of  any  original  difference 
in  structure,  but  on  account  of  especial, 
local,  and  predisposing  causes.  In  the 
words  of  Gothe,  the  originator  of  the 
theory,  plants  "develop  themselves  out 
of  themselves  progressively." 

METAMORPHO'SIS  (in  Zoology).  A 
term  denoing  a  series  of  changes  which 
insects  undergo,  both  in  their  outward 
form  and  their  internal  structure,  before 
they  arrive  at  their  perfect  condition. 
The  successive  states  of  existence  are 
L 


MET 

the  larva,  or  caterpillar ;  the  pupa,  nymph, 
or  chrysalis ;  and  the  imago,  or  perfect 
state. 

Fabricius  distinguishes  five  kinds  of 
metamorphosis.  1.  The  first  class  com- 
prises all  those  insects  in  which  the 
pupae,  being  entirely  without  legs,  are 
absolutely  motionless,  as  in  the  common 
house-fly;  these  are  called  coarctate. 
2.  The  second  kind  occurs  in  the  Lepi- 
doptera,  and  is  termed  obtected.  It  is 
seen  in  the  silk-worm,  which  wraps  itself 
in  a  silken  ball,  throws  off  its  last  skin, 
and  becomes  a  quiescent  pupa.  3.  The 
third  kind  of  metamorphosis  is  termed 
incomplete,  and  it  occurs  in  the  hymeno- 
pterous  and  in  many  coleopterous  insects, 
in  which  the  larva  is  deprived  of  feet  or 
other  external  organs,  or  possesses  these 
parts  in  a  very  imperfect  condition;  in 
the  pupa,  however,  they  are  perfectly 
distinct.  4.  A  semi-complete  metamor- 
phosis occurs  in  those  insects  whose 
larva  only  differs  from  the  imago  in  not 
being  possessed  of  wings.  5.  Metamor- 
phosis is  complete,  when  the  perfect  in- 
sect does  not  acquire  wings  at  all,  but 
precisely  resembles  the  pupa. 

METAPH Y'SICS  (/le-rci,  beyond,  0w<rtr, 
nature).  A  vague  term,  simply  denoting 
the  science  of  objects  beyond  that  which 
is  physical  and  sensible.  Generally 
speaking,  metaphysics  is  a  science  purely 
speculative,  which  investigates  the  ulti- 
mate grounds  of  being,  irrespectively  of 
experience.  In  this  country  it  usually 
denotes  the  philosophy  of  mind,  as  dis- 
tinguished from  that  of  matter. 

ME'TAPLASM  (jieraTrXa 0710c,  trans- 
formation). In  Grammar,  the  assumption 
of  a  present  or  nominative  for  the  derived 
tenses  of  verbs  or  cases  of  nouns,  as 
Treco)  for  Gireo-ov,  to  devdpos  for  devdpeai. 

METEMPSYCHO'SIS  (MeTejLnK'X«™, 
the  transferring  of  the  soul  from  one  body 
to  another).  The  transmigration  of  the 
soul ;  a  philosophical  or  religious  system 
taught  by  Pythagoras,  and  embraced  by 
the  Hindus,  Egyptians,  and  other  na- 
tions. According  to  this  doctrine,  the 
soul  passes  into  different  bodies,  under- 
going a  series  of  degradations  or  exalta- 
tions, until  it  becomes  reunited  with  the 
Supreme  Being,  with  which  it  is  iden- 
tified, "  as  a  river  at  its  confluence  with 
the  sea  merges  therein  altogether." 

METEO'RIC  STONES  ( /ue-rewpor, 
floating  in  the  air).  Aerolites.  Stones 
or  mineral  masses  which  have  fallen 
through  the  air,  accompanied  with  the 
disengagement  of  light  and  a  noise  like 
218 


MIC 

thunder.  They  are  composed  of  silica, 
iron,  and  magnesia,  with  small  propor- 
tions of  alumina,  lime,  nickel,  chrome, 
and  sulphur. 

METEORO'LOGY  (MeTea>Poc,  floating 
in  the  air,  \670f,  a  description).  Lite- 
rally, the  science  of  meteors;  but  the 
term  is  applied,  more  extensively,  to  the 
investigation  of  all  the  physical  causes 
which  affect  the  condition  of  our  globe  ; 
and  particularly  to  the  effects  of  light 
and  heat  on  the  earth,  the  ocean,  and 
the  atmosphere,  and  the  results  of  these 
agents  in  the  production  of  climate. 

ME'THYL  {fxeBv,  wine,  i/\n,  wood). 
The  newly-discovered  radical,  or  basyle, 
of  wood  spirit.  Methylic  ether  is  a  co- 
lourless gas,  the  oxide  of  methyl.  Methol 
is  a  liquid  produced  in  the  distillation  of 
wood. 

METONYMY  (neTwwfxia,  the  using 
of  one  word  for  another).  A  rhetorical 
figure,  by  which  an  idea  is  represented 
by  a  related  idea,  as  substance  by  quality, 
precedent  by  subsequent,  effect  by  cause. 
Thus :  "I  am  Sir  Oracle,"  for,  I  am  in- 
fallible. Again:  "  His' silver  hairs  will 
purchase  us  a  good  opinion." 

METOPO'SCOPY  (/lercoTrov,  the  fore- 
head, irKoirea,  to  examine).  The  art  of 
divining  by  inspection  of  the  forehead; 
practised  among  the  Romans,  and  in  the 
middle  ages. 

METRE.  The  French  standard  mea- 
sure of  length,  equivalent  to  39  371,  or 
very  nearly  39|  English  inches.  The 
French  measures  ascend  and  descend  in 
a  decimal  progression.    Thus, 

English  Inches. 

A  Millimetre  is    ...     .     -03937 

Centimetre -39371 

Decimetre 3*93710 

Metre 39-371 

Decametre  ....  39371 
Hecatometre  .  .  .  3937-1 
Chiliometre       .     .     39371 

ME'TRONOME  {nerpov,  a  measure, 
vono?,  a  musical  strain).  A  short  pen- 
dulum used  by  musicians  for  marking 
time,  which  may  be  made  to  vibrate 
quickly  or  slowly  as  occasion  requires  ; 
the  movements  of  the  pendulum  are 
regulated  by  wheels  and  a  spiral  spring. 

MIA'RGYRITE.  A  sulphur-salt,  first 
separated  byMohs  from  red  silver,  under 
the  name  of  hemiprismatic  ruby-blende. 

MI'ASCITE.  A  columnar  variety  of 
bitterspar,  intermixed  with  asbestos,  from 
Miaska  in  Siberia. 

MICA  (mico,  to  shine).  A  simple 
mineral,  having  a  shining  silvery  sur- 


M  I  C 


MID 


face,  and  capable  of  being  split  into  very 
thin  elastic  leaves  or  scales.  It  consists 
principally  of  flint  and  clay,  with  a  little 
magnesia  and  oxide  of  iron.  It  is  com- 
monly called  talc,  but  mineralogists  ap- 
ply this  term  to  a  different  mineral.  The 
brilliant  scales  in  granite  are  mica.  The 
varieties  which  have  been  examined  with 
reference  to  their  optical  properties  and 
chemical  constitution,  are  potassa-mica, 
the  most  common  variety,  which  has  two 
axes  ;  magnesia-mica,  which  has  but  one 
axis  ;  and  lithia-mica,  including  lepidote 
and  several  large-foliated  varieties  of 
what  was  formerly  called  common  mica. 

MICA-SLATE  or  SCHIST.  Micaceous 
schistus.  One  of  the  metamorphic  or 
crystalline  stratified  rocks,  of  the  hypo- 
gene  class,  which  is  characterized  by 
being  composed  of  a  large  proportion  of 
mica  united  with  quartz.  This  rock  is 
termed  laminar,  when  the  mica  occurs 
in  continuous  laminae,  alternating  with 
layers  of  quartz ;  granular  laminated, 
when  the  plates  of  mica  are  formed  of 
scales,  and  those  of  quartz  of  granules  or 
crystals ;  porphyritic,  when  either  of  the 
preceding  varieties  contains  crystals  of 
hornblende,  felspar,  or  garnet. 

MICA'CEOUS  ROCKS.  Rocks  of 
which  mica  is  the  chief  ingredient :  these 
are  mica- slate  and  clay-slate.  Though 
few  in  number,  they  are  extensively  dis- 
tributed. 

MI'CROCOSM  {fiiKpoi,  small,  xdc/xof, 
world).  A  term  fancifully  applied  by  the 
ancient  philosophers  to  man,  from  an 
idea  of  his  resemblance  in  miniature  to 
the  macrocosm,  or  great  world. 

MICROCO'SMIC  SALT.  A  triple  salt, 
consisting  of  the  phosphates  of  soda  and 
of  ammonia,  employed  as  a  flux  in  ex- 
periments with  the  blow-pipe. 

MICRO'METER  (/m»cpof,  small,  m<?- 
rpov,  a  measure).  An  instrument  adapted 
to  a  telescope,  for  the  purpose  of  measur- 
ing small  distances,  or  the  diameters  of 
objects  which  subtend  very  small  angles, 
as  those  of  the  celestial  bodies. 

MICRO'PYLE  (M'Kpos-,  small,  «-v\ti,  a 
gate).  The  botanical  designation  of  the 
foramen  of  the  ripe  seed,  comprising  the 
exostome  and  the  endostome  of  the  ovule, 
which  lead  to  the  internal  portion  of  the 
ovule,  or, the  nucleus. 

MFCROSCOPE  (/u«Kpo?,  small,  ano-new, 
to  view).  An  instrument  for  furnishing 
magnified  images  of  objects  so  minute 
that,  when  held  at  the  distance  of  dis- 
tinct vision,  viz  ,  from  eight  to  ten  inches 
of  the  eye,  the  unassisted  eye  is  inca- 
219 


pable  of  distinguishing  their  form  and 
component  parts.  This  end  is  obtained 
by  enlarging  the  angle  of  vision. 

1.  The  single  microscope  consists  of  a 
convex  lens,  with  a  very  short  focal  dis- 
tance. If  an  object  be  viewed  through  it 
at  less  than  its  focal  distance,  but  near 
to  the  focus,  the  rays  transmitted  through 
the  lens  will  be  rendered  more  conver- 
gent, and  an  eye  on  which  they  fall  will 
see  the  object  under  a  greater  angle  of 
vision,  i.  e.  it  will  see  the  object  magnified. 

2.  The  compound  microscope  consists 
of  two  or  more  convex  lenses,  or  of 
a  combination  of  concave  specula  and 
lenses.  The  former  is  termed  a  dioptric 
or  refracting,  the  latter  a  catoptric  or 
reflecting  microscope.  1.  In  its  simplest 
form,  the  refracting  microscope  consists 
of  only  two  convex  lenses,  that  nearest 
to  the  object  being  called  the  object-glass, 
the  other  the  eye-glass.  2.  In  reflecting 
microscopes,  the  place  of  the  object-glass 
is  occupied  by  a  concave  speculum,  which 
also  produces  an  inverted  image. 

3.  The  solar  microscope  is  nothing  more 
than  a  magic  lantern,  the  light  of  the 
sun  being  used  instead  of  that  of  a  lamp. 
It  consists  of  two  lenses,  one  of  which  is 
called  the  condenser,  because  it  is  em- 
ployed to  concentrate  the  rays  of  the 
sun,  in  order  to  illuminate  more  strongly 
the  object  to  be  magnified.  The  other  is 
a  double  convex  lens,  of  considerable 
power,  by  which  the  image  is  formed. 
To  these  is  added  a  plane  mirror,  for 
reflecting  the  rays  of  the  sun  on  the 
condenser. 

4.  The  oxy-hydrogen  microscope  is  an 
instrument  in  which,  instead  of  the  light 
of  the  sun  or  of  a  lamp,  an  intense  light 
is  employed,  by  means  of  the  combustion 
of  a  piece  of  lime  in  a  stream  of  oxy- 
hydrogen  gas.  A  cylinder  of  the  ignited 
lime,  of  half  an  inch  in  diameter,  diffuses 
a  light  greater  than  that  yielded  by  153 
wax  candles. 

MI'CROSCOTIUM.  The  Microscope ; 
a  modern  southern  constellation,  consist- 
ing of  ten  stars. 

MICROZOA'RIA  (pticpa  £wa,  small 
animals).  The  designation  given  by  De 
Blainville  to  the  infusory  animalcules  of 
the  earlier  writers.  They  are  distin- 
guished into  the  heteropoda  and  the 
apoda,  the  former  comprising  the  sec- 
tions rotiferae  and  ciliiferae,  the  latter 
having  no  external  appendages. 

MID- HEAVEN.  An  astronomical 
term  for  that  point  of  the  ecliptic  which 
is  on  the  meridian  at  any  given  moment. 
L2 


M  ID 


MIN 


MIDDLE  EPOCH.  A  geological  epoch 
characterized  by  the  presence  of  the  new 
red  sandstone,  a  formation  consisting  of 
sand  and  marl,  with  rare  local  interpola- 
tions of  limestone.     See  Geology. 

MIDDLE  LATITUDE  SAILING.  A 
nautical  term  employed  in  estimating  the 
difference  of  longitude  by  means  of  the 
differences. of  latitude  and  the  interme- 
diate departure;  this  departure  is  sup- 
posed to  be  an  arc  of  a  parallel  of 
longitude  at  the  intermediate  or  middle 
latitude. 

MIDDLE  TERM.  In  a  logical  syllo- 
gism, the  middle  term  (called  by  the  older 
logicians  "  argumenturn")  is  that  with 
which  each  of  the  other  terms,  the  major 
and  the  minor,  is  separately  compared,  in 
order  to  judge  of  their  agreement  or  dis- 
agreement with  each  other. 

MPDRIB.  Costa.  The  midrib  of  a 
leaf  is  the  principal  vein,  which  forms  a 
continuation  of  the  petiole  and  the  axis 
of  the  leaf;  from  this  all  the  other  veins 
diverge,  either  from  its  sides  or  its 
base. 

MI'EMITE.  A  variety  of  Werner's 
rhomb-spar,  or  magnesian  limestone, 
found  at  Miemo  in  Tuscany,  imbedded 
in  gypsum.  There  are  two  kinds  of 
miemite,  the  granular  and  the  prismatic. 

MILDEW.  A  disease  in  plants,  caused 
by  the  ravages  of  parasitic  fungi. 

MILE,  GEOGRAPHICAL.  Every 
degree  of  latitude  contains  60  geographi- 
cal miles,  and  these  are  always  under- 
stood to  be  used,  unless  other  miles  are 
specified.  They  must  not  be  confounded 
with  the  British  statute  mile,  which  is 
the  common  itinerary  measure  of  our 
country,  and  69|  of  which  are  contained 
in  a  degree  of  latitude.  Hence  a  great 
circle  contains  only  21,600  geographical 
or  nautical  miles,  whilst  it  contains 
24,869  common  or  statute  miles  ;  or,  a 
common  mile  is  to  a  geographical  mile 
as  21,600  to  24,869.  To  express  this 
proportion  in  feet,  we  must  say, 
21,600  :  24,869  \  \  5280ft.  \  6079089 ft. 
Hence  a  geographical  or  nautical  mile  is 
about  6079  English  feet. 

MILK  QUARTZ.  Rose  quartz.  A 
sub-species  of  rhomboidal  quartz,  with  a 
milk-white  or  rose-red  colour,  found  in 
Bavaria  in  beds  of  quartz  in  granite. 
It  is  probably  silica,  coloured  by  man- 
ganese. 

MILK  VESSELS.  Laticiferous  tissue. 

A  peculiar  tissue,  consisting  of  branched 

anastomizing  tubes,  lying  in  the  bark  or 

near  the  surface  of  plants,  and  containing 

220 


a  milky  juice.  They  are  also  called  vital 
vessels,  vessels  of  the  latex,  &c.  See 
Cinenchyma. 

MILKY  WAY.  An  astronomical  term 
applied  to  that  great  luminous  band 
which  stretches  across  the  sky,  from 
horizon  to  horizon,  and  which,  when 
examined  through  powerful  telescopes, 
is  found  to  consist  entirely  of  stars  scat- 
tered by  millions,  like  glittering  dust,  on 
the  black  ground  of  the  general  heavens. 

MILLEPO'RID^E  {mille,  a  thousand, 
porus.  a  pore).  A  tribe  of  lithophytous 
polyps,  comprising  those  in  which  the 
calcareous  axis  is  perforated  by  numerous 
conical  pores.  * 

MILLSTONE  GRIT.  A  coarse  sandy 
grit,  unlike  the  old  red  sandstone,  fre- 
quently replacing  or  covering  up  the 
coral  limestones  in  many  parts  of  Eng- 
land and  Ireland. 

MI'NERAL.  A  simple  mineral  is  a 
homogeneous  substance,  whether  simple 
in  an  elementary  point  of  view  or  not, 
which  presents  itself  in  certain  definite 
forms,  and  has  a  texture,  mode  of  break- 
ing, and  other  physical  properties,  as 
hardness  and  colour,  by  which  it  may  be 
distinguished  from  all  other  substances. 
The  science  which  treats  of  these  sub- 
stances is  called  mineralogy,  by  some 
oryctognosy ;  while  to  geology  belongs, 
among  other  subjects,  the  consideration 
of  their  aggregation  into  rocks,  which,  in 
a  geological  sense,  are  masses  of  mineral 
matter,  of  sufficient  extent  to  constitute 
an  essential  portion  of  the  solid  part  of 
the  globe. 

1.  Minerals  are  termed  crystalline, 
when  they  assume  particular  symmetri- 
cal forms,  as  that  of  a  cube  or  a  prism  ; 
amorphous,  when  they  occur  in  no  defi- 
nite form. 

2.  The  hardness  of  minerals  is  the 
resistance  which  they  oppose  to  the  sepa- 
ration of  their  parts.  Under  this  head 
(p.  159)  the  mode  of  testing  their  hard- 
ness is  explained.  Their  fragility  denotes 
the  comparative  ease  with  which  they 
may  be  fractured;  their  friability,  an 
imperfect  state  of  aggregation,  rendering 
them  easily  divisible  into  grains. 

3.  The  fracture  of  minerals,  or  the 
surface  exposed  when  they  are  broken 
by  a  hammer,  varies  considerably :  it 
may  be  even,  splintery,  scaly,  or  con- 
choidal— that  is,  concave  like  a  shell. 

4.  Minerals  are  transparent,  when  they 
allow  sufficient  light  to  pass  through 
them  to  enable  a  body  to  be  distinguished 
when  placed  behind  them;  translucent, 


MIN 


MIS 


when  they  admit  light,  but  are  not  trans- 
parent ;  opaque,  when  they  transmit  no 
light,  even  when  reduced  to  a  finely 
laminated  state.  The  lustre,  or  degree 
in  which  the  surface  of  minerals  reflects 
light,  is  various  :  it  may  be  glimmering, 
glassy,  pearly,  resinous,  silky,  metallic, 
adamantine. 

5.  The  texture  of  minerals  is  regular 
or  irregular ;  lamellar,  when  it  presents 
the  appearance  of  thin  plates ;  fibrous, 
when  composed,  as  it  were,  of  threads  or 
filaments ;  radiating,  when  the  fibres 
converge  towards  a  point. 

MINERAL  CAOUTCHOUC.  A  va- 
riety of  bitumen,  resembling  caoutchouc 
in  elasticity  and  softness,  and  in  remov- 
ing pencil-marks. 

MINERAL  CHARCOAL.  A  fibrous 
variety  of  non-bituminous  mineral  coal. 

MINERAL  GREEN.  A  hydrated  sub- 
carbonate  of  copper,  used  as  a  pigment. 

MINERAL  YELLOW.  Patent  yellow. 
A  pigment  consisting  of  chloride  and 
protoxide  of  lead. 

MINERALIZATION.  The  process  of 
converting  a  substance  into  a  mineral. 
A  metal  combined  with  oxygen,  sulphur, 
&c,  loses  its  metallic  properties,  and 
becomes  mineralized.  The  latter  bodies 
are  then  termed  mineralizers :  thus,  in 
the  native  oxides,  oxygen  is  called  the 
mineralizer;  in  the  ores  of  lead  and 
copper,  sulphur  is  the  mineralizer,  &c. 

MINERA'LOGY.  The  science  which 
relates  to  the  accurate  description,  and 
natural  classification  of  minerals.  That 
branch  of  the  subject  which  relates  to 
the  arrangement  of  the  descriptive  cha- 
racters of  minerals,  for  the  purpose  of 
distinguishing  them  from  one  another, 
is  more  properly  an  art. 

MI'NIMUM  (superl.  of  parvus,  small). 
The  least  possible  quantity  or  effect,  as 
opposed  to  maximum,  or  the  greatest 
possible. 

MI'NIUM.  Red  lead  or  vermilion  ;  an 
oxide  of  lead,  of  an  intensely  red  colour, 
employed  as  a  pigment.  Native  minium, 
from  Hessia,  Siberia,  &c,  is  probably 
produced  by  the  decomposition  of  galena. 

MINOR  TERM.  In  Logic,  the  minor 
term  of  a  categorical  syllogism  is  the 
subject  of  the  conclusion.  The  minor 
premiss  is  that  which  contains  the  minor 
term.  In  hypothetical  syllogisms,  the 
categorical  premiss  is  called  the  minor. 

MINUTE.  The  sixtieth  part  of  a  de- 
gree of  a  circle.  Minutes  are  denoted  by 
one  acute  accent,  thus  (') ;  the  second, 
or  sixtieth  part  of  a  minute,  by  two  such 
221 


accents  (") ;  and  the  third  by  three  ('"). 
See  Hour. 

MFOCENE  (uetW,  less,  Katvo?,  recent). 
A  division  of  tertiary  strata,  intervening 
between  the  Eocene  and  Pliocene  forma- 
tions; so  called,  because  a  minority  of 
its  fossil  shells  are  referable  to  living 
species. 

MIRACH,  or  0  ANDROMEDA.  A 
star  of  the  second  magnitude,  in  the 
constellation  Andromeda. 

MIRAGE.  A  meteorological  phenome- 
non, depending  partly  on  the  vapour  of 
the  atmosphere,  and  partly  on  the  inter- 
mixture of  strata  of  air  of  different  tem- 
peratures and  densities.  It  assumes  the 
appearance  of  a  sheet  of  water,  often 
exhibiting  the  reflected  or  inverted 
images  of  distant  objects.  This  unusual 
refraction  frequently  occurs  when  there 
intervenes  between  the  spectator  and  the 
objects  an  expanse  of  smooth  water,  as 
on  the  Oldenburg  coast  of  the  North  Sea, 
where  it  is  called  Kimmung ;  or  as  at  the 
Straits  of  Messina,  where  it  is  called 
Fata  Morgana. 

MIRROR  (mirer,  French,  to  look  at). 
Any  polished  body  which  is  impervious 
to  the  rays  of  light,  and  reflects  them 
equally,  so  as  to  exhibit  the  images  of 
objects  placed  before  it.  When  formed 
of  metal,  it  is  sometimes  termed  specu- 
lum, the  Latin  term  for  a  looking-glass. 

1.  Plane  Mirror.  That  which  has  a 
plane  surface,  as  the  common  looking- 
glass. 

2.  Concave  Mirror.  That  which  has  a 
hollow  surface,  which  collects  the  rays 
and  reflects  them  to  a  focus  in  front  of 
the  mirror,  thereby  enlarging  the  image 
of  the  object. 

3.  Convex  Mirror.  That  which  has  a 
convex  surface,  which  disperses  the  rays, 
and  consequently  diminishes  the  image 
of  the  object.  These  concave  and  convex 
surfaces  are  formed  of  different  curves, 
according  to  the  purposes  intended,  and 
may  be  spherical,  parabolic,  or  elliptical. 
Mirrors  with  mixed  surfaces  are  either 
cylindrical  or  conical.  See  Burning- 
glass. 

MISPI'CKEL.  Arsenical  pyrites;  an 
arsenio-sulphuret,  some  varieties  of 
which,  containing  accidentally  admixed 
silver,  constitute  Werner's  weiss-ertz. 

MIST.  A  meteorological  phenomenon, 
occasioned  by  the  vapour  of  the  atmo- 
sphere becoming  visible;  and  this  is  a 
consequence  of  the  temperature  of  the 
air  being  reduced  below  that  of  the 
vapour. 

L3 


MIS 


MOL 


MISY.  A  designation  of  green  vitriol, 
or  sulphate  of  iron,  as  it  occurs  in  the 
form  of  yellow  scales,  in  the  Hartz. 

MI'TRINiE.  Mitre-shells ;  a  sub- 
family of  the  Volutidce,  or  volutes,  named 
from  the  typical  genus  mitra ;  the  spire 
is  always  acute,  generally  longer  than  the 
aperture,  and  the  lower  plaits  smallest ; 
the  foot  is  small,  not  dilated  on  the  sides, 
and  the  siphon  rather  long. 

MIXTURE  and  COMPOUND.  In  a 
chemical  mixture,  the  aggregate  particles 
can  be  separated  by  mechanical  means, 
and  the  proportion  of  the  different  consti- 
tuents determined;  in  a  chemical  com- 
pound, no  mechanical  power  can  separate 
the  constituent  particles :  a  new  substance 
is  formed,  which  possesses  no  properties 
in  common  with  the  original  ingredients. 

MNEMO'NICS  (hvwovikos,  belonging 
to  memory).  A  term  applied  to  any  sys- 
tem in  which  the  memory  of  particular 
objects  is  exercised  by  artificial  means. 
The  principle  of  all  such  systems  is,  to 
associate  in  our  minds  two  notions,  one 
of  which  is  more  easily  remembered  than 
the  other,  but,  in  consequence  of  the 
association,  is  always  followed  by  that 
other.  t 

MOBI'LITY  {mobilis,  moveable).  A 
property  of  matter  by  which  it  is  capable 
of  being  put  into  motion  by  the  action  of 
a  force  which  is  sufficient  to  overcome 
its  inertia. 

MOCHA  STONE.  A  translucent  chal- 
cedony, containing  dark  outlines  of  arbor- 
ization, like  vegetable  filaments,  and 
named  from  Mocha,  in  Arabia,  where  it 
is  chiefly  found. 

MODAL.  In  Logic,  a  modal  categori- 
cal proposition  is  one  which  asserts  that 
the  predicate  exists  in  the  subject  in  a 
certain  mode  or  manner,  as  "accident- 
ally," "  wilfully,"  &c. 

MODERN  EPOCH.  In  Geology,  the 
present  period  comprehends  all  those 
deposits  which  owe  their  origin  to  causes 
now  in  action,  and  has  reference  to  the 
phenomena  which  are  taking  place  at  the 
surface  of  the  earth.     See  Geology. 

MO'DULUS.  1.  In  the  theory  of  loga- 
rithms, the  modulus  is  the  number  by 
which  all  the  logarithms  in  one  scale  of 
notation  must  be  multiplied,  in  order  to 
adapt  them  to  the  same  number  of  an- 
other scale.  Thus  the  modulus  of  con- 
version between  the  common  logarithms 
and  the  Napierean  or  hyperbolic  scale,  is 
0*43,429,448.  2.  In  Physics,  the  modulus 
of  elasticity  is  a  numerical  co-efficient, 
which  is  constant  for  the  same  body,  but 
222 


variable  for  different  bodies ;  and  which 
has  no  influence  on  the  law  of  elasticity, 
though  it  serves  to  measure  its  effects. 

MO'HSITE.  Crystallized  titaniate  of 
iron,  found  in  Dauphiny. 

MOIRE'E  METALLIQUE.  Crystal- 
lized tin-plate,  obtained  by  pouring  on 
heated  tin-plate  a  mixture  of  two  parts 
of  nitric  acid,  and  three  of  muriatic  acid 
diluted  with  eight  parts  of  water.  When 
varnished,  it  is  worked  into  ornamental 
vessels. 

MOLA'SSE  (molle,  French,  soft).  A 
provincial  name  for  a  soft  green  sand- 
stone, associated  with  marl  and  conglo- 
merates, belonging  to  the  Miocene  Ter- 
tiary Period,  extensively  developed  in 
the  lower  country  of  Switzerland. 

MOLE'CULAR  ATTRACTION.  That 
mode  of  attraction  which  operates  upon 
the  particles,  or  molecules,  of  a  body,  as 
distinguished  from  the  attraction  of  gra- 
vitation. According  to  the  molecular 
theory,  all  bodies  are  viewed  as  aggre- 
gates of  minute  particles,  atwms,  or  mole- 
cules, and  are  formed  by  the  attractive 
and  repulsive  forces  acting  on  them  at 
immeasurably  small  distances. 

MOLECULE  (dim.  of  moles,  a  mass). 
A  minute  particle  of  a  mass  or  body. 
It  differs  from  atom,  in  being  always  con- 
sidered as  a  portion  of  some  aggregate. 

1.  Complex  organic  molecule.  An 
association  of  two  or  more  binary  com- 
pounds, comparatively  simple  in  consti- 
tution, often  isolable  substances  and  pos- 
sessed of  considerable  stability. 

2.  Integrant  molecules.  The  name 
given  by  Haiiy  to  the  last  particles  into 
which  the  nucleus  of  a  crystal  can  be 
mechanically  divided. 

3.  Molecules,  active.  Minute  moving 
particles,  found  in  all  vegetable  matter 
when  rubbed  in  pieces  and  examined 
under  a  powerful  microscope. 

MO'LISITE.  The  mineralogical  name 
of  the  crystallized  titaniate  of  iron  of 
Dauphiny. 

MOLLUSC  A  (mollis,  soft).  A  term 
employed  by  Cuvier  to  designate  the 
fourth  grand  division  of  the  animal 
world,  and  founded  upon  the  unimpor- 
tant circumstance  that  the  beings  to 
which  it  is  applied  have  soft  bodies,  un- 
supported by  any  internal  or  tegumentary 
framework  of  sufficient  density  to  merit 
the  name  of  skeleton.  These  animals 
belong  to  the  Hetero-gangliata  of  Owen, 
the  Cyclo-gangliata  of  Grant.  See  Zoo- 
logy. 

MOLYBDE'NUM  in6\v/3ios,  lead).  A 


MON 


MON 


white  metal  closely  allied  to  tungsten. 
Its  name  was  derived  from  the  resem- 
blance of  its  native  sulphuret,  or  molyb- 
dena-glance,  to  lead. 

MOLY'BDIC  ACID.  Ochry  molybde- 
num. An  acid  obtained  from  the  native 
sulphuret  of  molybdenum,  in  the  form 
of  a  yellow  powder.  Its  salts  are  termed 
molybdates.  The  molybdate  of  lead,  or 
yellow  lead  ore,  occurs  as  a  massive  mi- 
neral, lamelliform,  and  crystallized  in 
splendid  groups  on  compact  limestone, 
&c. ;  chiefly  from  Bleiberg  in  Carinthia. 

MOME'NTUM.  A  term  in  physics 
signifying  the  force  of  percussion,  or 
the  intensity  of  a  moving  body ;  and 
this  is  always  equal  to  the  quantity 
of  matter  multiplied  into  the  velocity. 
Thus,  a  ball  of  four  pounds'  weight, 
moving  at  the  rate  of  eighteen  feet  in  a 
second,  has  double  the  momentum  of  a 
ball  of  three  pounds'  weight,  moving  at 
the  rate  of  twelve  feet  per  second,  for 
4  x  18  is  double  of  3  x  12. 

If  the  momenta  of  two  or  more  forces, 
acting  in  opposite  directions  on  a  solid 
body,  be  equal,  the  body  will  continue 
at  rest ;  and  this  condition  is  called  the 
equilibrium,  or  statical  momentum  of  the 
forces. 

MON-,  MONO-  (/ioi/o?,  single,  alone). 
A  Greek  prefix,  denoting  unity. 

1.  Mon-adelphia  (a6e\<pot,  a  brother). 
The  sixteenth  class  of  plants  in  the  Lin- 
naean  system,  in  which  the  filaments  are 
all  united  into  one  tube. 

2.  Mon-andria  (ui^p,  a  man).  The 
first  class  of  plants  in  the  Linnaean  sys- 
tem, containing  only  one  stamen. 

3.  Mono-carpous  {Kapirot,  fruit).  Bear- 
ing fruit  only  once,  and  dying  after  fruc- 
tification, as  wheat.  This  is  the  character 
of  what  are  commonly  called  annual 
plants,  and  of  a  few  others,  which,  like 
the  American  aloe,  although  they  may 
live  for  many  years,  produce  flowers  and 
fruit  only  once,  and  then  die. 

4.  Mono-ceros  (»cepac,  a  horn).  The 
Unicorn ;  a  modern  southern  constella- 
tion, consisting  of  thirty  one  stars. 

5.  Mono-chlamydece  (x\a/uuf,  a  tunic). 
A  sub-class  of  exogenous  plants,  in  which 
the  flowers  have  only  one  envelope,  viz. 
a  calyx. 

6.  Mono-chord  (xop6i],  a  string).  Sono- 
meter. An  apparatus  for  exhibiting  the 
phenomena  of  sonorous  bodies  and  the 
ratios  of  their  vibrations.  In  its  most 
simple  construction,  it  consists  of  a  single 
string  of  wire  or  catgut  strained  by  means 
of  two  pins  across  two  wooden  bridges,  I 

223  ' 


which  are  fastened  into  a  strong  board ; 
the  part  of  the  board  beneath  the  string 
is  graduated,  so  that  the  latter  may  be 
readily  made  to  vibrate  in  any  required 
number  of  parts. 

7.  Mono-chroite.  Subsesquichromate 
of  lead  ;  one  of  the  ores  containing  chro- 
mium, occurring  with  chromate  of  lead 
in  the  Ural. 

8.  Mono-chromatic  (xptfyza,  colour). 
Having  only  one  colour  ;  a  term  applied 
to  a  lamp  which,  being  fed  with  certain 
substances,  yields  a  flame  of  only  one 
colour;  and,  hence,  all  objects  viewed  by 
this  light  are  deficient  in  those  varied 
hues  which  they  reflect  when  viewed  by 
solar  light  or  that  from  ordinary  com- 
bustibles. 

9.  Mono-cotyledons  (kotu\m3«v,  a  seed- 
lobe).  Plants  which  have  only  one  coty- 
ledon, or  seed-lobe.  This  structure  of 
the  embryo  corresponds  with  the  endo- 
genous structure  of  the  stem ;  and  hence, 
monocotyledon  and  endogen  are  convert- 
ible terms. 

10.  Mon-oecia  (otKof,  a  house).  The 
twenty-first  class  of  plants  in  the  Lin- 
nean  system,  in  which  the  stamens  and 
pistils  grow  on  separate  flowers,  but  on 
the  same  individual,  as  in  hazel,  birch, 
oak,  &c. 

11.  Mono-gram  (ypdnfia,  a  written 
letter).  A  mark  or  cipher  consisting  of 
one  letter,  which  is  formed  by  the  inter- 
lacing of  two  or  more  letters,  employed 
as  an  abbreviation,  especially  on  ancient 
coins. 

12.  Mono-gynia  (71/1///,  a  female).  The 
name  given  by  Linnaeus  to  those  orders 
of  plants,  in  which  each  flower  contains 
only  one  pistil. 

13.  Mono-lith  (\i9ov,  a  stone).  A  pillar 
consisting  of  a  single  stone,  as  the 
obelisk  of  Luxor,  the  Zodiac  of  Den- 
derah,  &c. 

14.  Mono-mera  (nepo?,  a  part).  A  sec- 
tion of  homopterous  insects,  in  which  the 
tarsi  have  only  one  joint,  as  in  the 
Coccidce,  or  Scale  Insects. 

15.  Mono-morphous  (fxop<pi],  form).  Of 
a  single  form;  a  term  proposed  by  Mr. 
Westwood  for  certain  neuropterous  in- 
sects, which,  in  their  larva  state,  are 
similar  in  form  to  the  perfect  insect, 
though  wingless. 

16.  Mono-myaria  (/xur,  a  muscle).  A 
general  name  for  bivalves,  whose  shell 
is  closed  by  a  single  adductor  muscle,  as 
in  the  oyster  and  the  pecten.  See  Di- 
myaria. 

17.  Mono-neura  {vevpov,  a  nerve).    A 

L4 


MON 


MON 


name  given  by  Rudolphi  to  those  animals 
which  were  supposed  to  possess  only  the 
ganglionic  system  of  nerves,  as  the  mol- 
lusca  and  the  insects. 

18.  Mono-petalous  (7rera\ov,  a  leaf). 
Having  a  single  petal,  as  applied  to  the 
corolla  of  plants.  The  difference,  how- 
ever, between  a  mono-petalous  and  a 
poly-petalous  corolla  is,  that  in  the  former 
the  leaves  are  united,  whereas  in  the 
latter  they  are  distinct.  A  more  proper 
term  for  the  former  is  gamo-petalous, 
which  indicates  cohesion. 

19.  Mono-phyllous  {<pv\\ov,  a  leaf).  A 
term  sometimes  employed  as  synonymous 
with  monosepalous,  and  denoting  cohe- 
sion of  the  sepals,  or  a  gamosepalous 
calyx. 

20.  Mono-pleurohranchians  (wAcwpa, 
the  side,  /3pu7x*a>  gills).  An  order  of 
the  Paracephalophora,  in  which  the 
branchiae  are  more  or  less  completely 
covered  by  a  portion  of  the  mantle,  and 
situated  on  the  right  side  of  the  body. 

21.  Monosepalous.  Having  a  single 
sepal,  or  calyx- leaf.  The  term  gamo- 
sepalous is  preferable,  for  the  reason 
assigned  under  the  term  mono-petalous. 

22.  Mono-thalamous  (0d\a/uof ,  a  cham- 
ber). A  term  applied  to  a  shell  which 
forms  a  single  chamber,  as  that  of  the 
argon  auta. 

23.  Mono-thyra  {66pa,  a  door).  A  term 
applied  by  Aristotle  to  all  spiral  univalve 
shells.    See  Dithyra. 

24.  Mono-tremata  (Tpdw,  to  bore  a 
hole).  An  order  of  Mammalia,  charac- 
terized by  the  presence  of  a  common 
cloacal  outlet  for  the  excremental  and 
the  generative  products.  They  are  ovo- 
viviparous  animals,  being  intermediate 
between  the  truly  viviparous  mammalia, 
and  the  oviparous  birds  and  reptiles.  The 
order  contains  only  two  species,  the 
echidna  or  spiny  ant-eater,  and  the  orni- 
thorrhynchus  or  duck-billed  platypus. 

MONAD  (/uovar,  unity).  The  smallest 
of  all  visible  animalcules,  spoken  of  by 
Buffon  and  his  followers  as  constituting 
the  elementary  molecule  of  organic 
beings.  Ehrenberg  computed  that  a  sin- 
gle drop  of  liquid  may  contain  500,000,000 
monads,  a  number  equal  to  that  of  all 
the  human  beings  on  the  surface  of  the 
globe. 

1.  Monad  of  the  Physiologists.  An 
elementary  particle  of  an  organic  body. 
Thus,  the  primary  cell  or  germ  from 
which  all  the  other  cells  of  the  brain  are 
produced,  is  termed  the  primary  monad  ; 
and  the  secondary  cells  or  particles,  pro- 
224 


duced  by  this,  are  termed  secondary 
monads. 

2.  Monad  of  the  Metaphysicians.  An 
active  kind  of  principle,  endued  with 
perception  and  appetite,  ascribed  to 
each  elementary  particle  of  matter.  The 
mutual  reaction  of  the  mind  and  body 
upon  each  other,  accordingly,  consists  of 
the  action  of  the  mental  monad  upon  the 
internal  states  of  the  monads  of  the  body, 
and  vice  versa. 

MONGOLIAN  RACE.  One  of  the 
five  principal  races  of  mankind,  in  which 
the  head  is  almost  square,  the  cheek- 
bones projecting  outwards,  the  nose  flat, 
the  face  broad  and  flattened,  with  the 
parts  imperfectly  distinguished,  the  in- 
ternal angle  of  the  eye  depressed  towards 
the  nose. 

MO'NITOR.  An  animal  of  the  sau- 
rian or  lizard  tribe,  some  species  of 
which  are  found  in  both  the  fossil  and 
the  recent  state. 

MONS  MENELAUS.  A  modern 
northern  constellation  consisting  of 
eleven  stars. 

MONSOO'NS  (mooseem,  Malay,  a  sea- 
son). Periodical  winds,  which  blow 
half  the  year  from  one  quarter,  and  the 
other  half  from  the  opposite  direction. 
From  April  to  October  a  south-west  wind 
prevails  north  of  the  equator,  southward 
of  this  a  south-east  wind ;  from  October 
to  April,  a  north-east  wind  prevails  north 
of  the  equator,  and  a  north-west  between 
the  equator  and  10°  of  south  latitude. 
The  monsoons  occur  in  the  Bay  of  Ben- 
gal, the  Arabian  Sea,  the  Mozambique 
Channel,  on  the  coasts  of  Sumatra  and 
Java,  along  the  coast  of  China,  and  off 
the  western  coast  of  New  Holland. 

MONTGOLFIER.  An  air-balloon,  or 
aerostat,  made  of  paper,  with  a  large 
opening  below,  where  fire  is  applied  for 
the  purpose  of  rarefying  the  contained 
air,  until  it  is  of  less  specific  gravity  than 
the  atmospheric  air.  It  is  named  from 
its  inventor. 

MONTH.  1.  The  average  sidereal 
month,  or  complete  circuit  of  the  hea- 
vens, comprises  a  period  of  27d.  7h.  43m. 
11.5s.  2.  The  average  lunation,  common 
month,  or  interval  between  two  conjunc- 
tions with  the  sun,  consists  of  29d.  12h. 
44m.  2.9s.  3.  The  average  anomalistic 
month,  or  revolution  from  perigee  to 
perigee,  consists  of  27d.  13h.  18m.  37.4s. 
4.  The  average  tropical  month,  or  period 
from  the  vernal  equinox  to  the  vernal 
equinox  again  (the  equinox  being  in  re- 
trograde   motion),    consists  of  27d.  7h. 


M  OR 


MOT 


43m.  4.7s.  5.  The  average  nodical  month, 
or  interval  of  time  from  a  node  to  a  node 
of  the  same  kind,  comprises  27d.  5h.  5m. 
36.0s.  The  quantities  of  these  months 
are  here  reckoned  in  mean  solar  days. 

MONTMA'RTRITE.  A  yellowish 
massive  mineral,  found  at  Montmartre, 
near  Paris,  consisting  of  the  sulphate  and 
the  carbonate  of  lime. 

MOOD  (in  Grammar).  A  mood  ex- 
presses the  manner  in  which  the  action 
or  state  denoted  by  the  verb  exists,  as 
being  certain,  contingent,  &c. 

MOOD  (in  Logic).  The  mood  of  a 
categorical  syllogism  is  the  designation  of 
its  three  propositions,  in  the  order  in 
which  they  stand,  according  to  their 
quantity  and  quality.  Only  eleven  moods 
can  be  used  in  a  legitimate  syllogism. 

MOON.  A  heavenly  body  which 
moves  round  the  earth  in  the  period  of  a 
lunar  month,  accompanying  the  earth, 
as  a  satellite,  in  its  orbit  round  the  sun. 
The  average  distance  of  the  moon  from 
the  earth  is  237,000  miles. 

MOON-CULMINATING.  A  term 
applied,  in  astronomy,  to  those  stars 
which  pass  the  meridian  soon  before  or 
after  the  moon.  In  the  nautical  almanac, 
these  stars  are  selected  for  each  day,  and 
their  right  ascensions  are  given  for  their 
Greenwich  meridian  transits. 

MOONSTONE.  Adularia.  Naker 
felspar,  principally  found  on  Mount  St. 
Gothard.  It  is  the  famous  petuntse  of  the 
Chinese,  which  constitutes  the  vitrifying 
ingredient  of  their  porcelain.  The  fine 
variety  from  Ceylon,  when  cut  en  cabo- 
chon,  is  called  moonstone.  See  Sun- 
stone. 

MORAINE.  A  mass  of  debris  accu- 
mulated along  the  anterior  edge  and 
lateral  margins  of  some  of  the  larger 
glaciers,  in  the  form  of  a  long  dyke  or 
parapet,  called  in  the  Tyrol  trockne 
muren,  and  in  Savoy  moraine.  In  Ice- 
land, where  the  glaciers  are  called  jokiil, 
the  moraines  are  called  joki'Usgidrde. 

MORDANT  (mordeo,  to  bite).  A  sub- 
stance employed  in  dyeing,  which  has  an 
affinity  both  for  the  colouring  matter  and 
for  the  stuff  to  be  dyed  ;  the  combination 
of  the  colour  with  the  texture  of  the 
stuff  is  thus  aided  by  a  kind  of  double 
decomposition.  These  substances  were 
supposed,  in  the  infancy  of  the  art,  to 
seize  the  fibres  by  an  agency  analogous 
to  that  of  the  teeth  of  animals. 

MO'ROXITE.    Norwegian  apatite;  a 
phosphate  of  lime,  of  a  blue-green  colour, 
occurring   native   in   combination  with 
225 


fluoride  of  calcium,  in  the  form  of  hex- 
agonal prisms. 

MORO'XYLIC  ACID  {fxopov,  the 
mulberry,  £v\ov,  wood).  Moric  acid. 
An  acid  procured  from  the  bark  of  the 
mulberry-tree,  forming  compounds  with 
salifiable  bases,  called  mor oxalates. 

MO'RPHIA  (Morpheus,  the  god  of 
sleep).  A  vegetable  alkali  existing  in 
opium,  of  which  it  constitutes  the  nar- 
cotic principle. 

MORPHO'LOGY  (nop<pyn,  form,  \6yos, 
a  description).  The  history  of  the  mo- 
difications of  form  which  the  same  organ 
undergoes  in  different  animals  or  plants. 
See  Metamorphosis. 

MORTAR  CEMENT.  A  mixture  of 
lime  and  siliceous  sand,  the  former  being 
in  the  state  of  hydrate  or  slaked  lime. 
Hydraulic  mortar  is  obtained  from  con- 
cretionary masses  found  in  marl,  and 
also  in  the  form  of  isolated  blocks  in  the 
bed  of  the  Thames. 

MOSAIC  GOLD,  (aurum  musivum). 
The  alchemical  name  of  the  bisulphuret 
of  tin.  It  is  produced  in  fine  flakes  of  a 
beautiful  golden  colour,  and  is  used  as  a 
pigment. 

MOSASAU'RUS.  The  saurian  of  the 
Meuse  ;  a  gigantic  extinct  aquatic  lizard, 
nearly  allied  to  the  monitor,  and  found 
in  the  cretaceous  series,  chiefly  on  the 
banks  of  the  Meuse. 

MO'SCHIDjE  (moschus,  the  musk 
deer).  The  Musk  Deer  tribe ;  a  family 
of  the  Ruminantia,  differing  little  from 
the  rest  of  the  order,  except  in  the  ab- 
sence of  horns. 

MO'SCHUS.  A  quadruped  resembling 
the  chamois  or  mountain  goat,  from 
which  the  perfume  musk  is  obtained. 

MOTACILLI'NjE  {motacilla,  the  wag- 
tail). Motacilline  birds,  or  Wag-tails ; 
a  family  of  the  Cantatrices  of  Mac  Gil- 
livray,  with  slender  form,  rather  short 
neck,  and  oblong  head;  readily  distin- 
guished from  the  allied  families  by  the 
elongated  tail  and  peculiar  form  of  the 
wings. 

MOTHER  OF  PEARL.  A  term  ap- 
plied to  shells  composed  of  alternate 
layers  of  coagulated  albumen  and  carbo- 
nate of  lime. 

MOTHER  WATER.  The  liquid 
which  remains  when  sea  water,  or  any 
other  solution  containing  various  salts, 
has  been  evaporated,  and  the  crystals 
removed.  The  mother  water  contains 
deliquescent  salts,  and  any  existing  im- 
purities. 

MOTION.    The  continued  change  of 
L5 


MOT 


MOU 


place  of  a  body,  or  of  any  parts  of  a  body ; 
for,  in  the  cases  of  a  globe  turning  on  its 
axis,  and  of  a  wheel  revolving  on  a  pivot, 
the  parts  of  these  bodies  change  their 
places,  while  the  bodies  themselves  re- 
main stationary. 

1.  Uniform  motion  is  that  of  a  body 
which  passes  over  equal  spaces  in  equal 
times.  It  is  produced  by  a  force  having 
acted  on  a  body  once,  and  having  ceased 
to  act,  as  the  stroke  of  a  bat  on  a  cricket- 
ball.  Were  there  no  opposing  force,  as 
gravity,  the  motion  of  such  a  body  would 
be  uniform. 

2.  Retarded  motion  is  produced  by 
some  force  acting  on  a  body  in  a  direc- 
tion opposed  to  that  which  first  put  it  in 
motion,  and  thus  gradually  diminishing 
its  velocity. 

3.  Accelerated  motion  is  produced  when 
the  force  which  puts  a  body  in  motion 
continues  to  act  upon  it  during  its  mo- 
tion, so  that  its  velocity  is  continually 
increased. 

4.  In  cases  of  accelerated  and  of  re- 
tarded velocity,  a  distinction  is  observed 
between  the  initial  and  the  final  velocity 
of  a  body :  the  former  is  exhibited  by 
the  body  when  it  commences  its  motion  ; 
the  latter  only  after  the  lapse  of  a  certain 
time :  both  are  measured  by  the  space 
which  the  body  would  have  passed  over, 
in  one  second,  with  the  uniform  initial  or 
final  velocity,  as  the  case  may  be. 

5.  Reflected  motion  is  produced  when 
a  body  is  turned  out  of  a  straight  line  by 
some  force  independent  of  gravity ;  it  is 
the  result  of  re-action  being  contrary  to 
action.  If  a  ball  be  thrown  against  a 
wall,  it  rebounds,  in  consequence  of  the 
re-action  of  the  wall  against  which  it  is 
struck,  and  it  is  said  to  have  reflected 
motion. 

6.  Simple  motion  is  that  which  results 
from  the  operation  of  a  single  force.  But 
when  two  or  more  forces  act  in  different 
directions  on  the  same  body,  at  the  same 
time,  the  motion  so  produced  is  called 
compound;  and  the  single  force  which 
represents  the  combined  effects  of  all  the 
forces,  is  called  the  resultant. 

7.  Circular  motion  is  the  motion  of  a 
body  in  a  ring,  or  circle,  and  is  produced 
by  the  action  of  two  forces.  By  one  of 
these  forces  the  moving  body  tends  to 
fly  off  in  a  straight  line,  while  by  the 
other,  it  is  drawn  towards  the  centre,  and 
thus  it  is  made  to  revolve,  or  move  round 
in  a  circle.  The  force  by  which  a  body 
tends  to  go  off  in  a  straight  line  is  called 
the  centrifugal  force;  that  which  draws 

226 


it  towards  the  centre,  is  called  the  cen- 
tripetal force. 

8.  In  curvilinear  motion  the  direction 
of  the  body  is  neither  straight  forward 
nor  diagonal,  but  through  a  line  which  is 
curved.  This  kind  of  motion  may  be  in 
any  direction  ;  but  when  it  is  produced 
in  part  by  gravity,  its  direction  is  always 
towards  the  earth.  A  stream  of  water 
from  an  aperture  in  the  side  of  a  vessel, 
as  it  falls  towards  the  ground,  is  an  ex- 
ample of  a  curved  line  ;  and  a  body  pass- 
ing through  such  a  line,  is  said  to  have 
curvilinear  motion. 

9.  It  may  happen  that  an  object  is  in 
motion,  as  well  as  the  spectator,  in  which 
case,  the  motion  of  the  latter  is  trans- 
ferred to  the  former,  and  the  whole  mo- 
tion of  the  object,  compounded  of  that 
which  it  has  of  its  own,  and  that  which 
it  appears  to  have  from  the  motion  of  the 
spectator,  is  called  the  apparent  or  rela- 
tive motion. 

MOTION,  CENTRE  OF.  That  point 
which  remains  at  rest,  while  all  the  other 
parts  of  a  body  move  about  it. 

MOUNTAIN.  A  considerable  eleva- 
tion of  the  surface  of  the  earth,  attaining 
a  height  of  more  than  two  thousand  feet. 
A  chain  of  mountains  is,  strictly  speak- 
ing, a  series  of  which  the  bases  are  con- 
tinuous. A  hill  is  merely  a  small  moun- 
tain, and  the  lowest  elevations  of  this 
kind  are  called  hillocks  or  mounds.  A 
mountain  of  a  conical  form,  with  the 
summit  narrow,  is  named  a  cone;  when 
of  the  same  form,  but  more  massy,  and 
with  the  summit  depressed  and  rounded, 
it  is  a  dome;  these  are  of  volcanic  origin. 
See  Platform  and  Peak. 

MOUNTAIN  BLUE.  Blue  copper,  or 
carbonate  of  copper,  the  more  remark- 
able varieties  of  which  are  those  from 
Chessy,  and  from  the  Bannat,  combined 
with  various  substances.  Mountain  green 
is  the  common  copper  green,  also  a  car- 
bonate. 

MOUNTAIN  CORK.  The  elastic 
variety  of  asbestos.  Mountain  leather 
is  the  tough  variety.  When  it  occurs  in 
very  thin  pieces,  it  is  called  mountain 
paper.  The  ligniform  variety  is  named 
mountain  or  rock  wood. 

MOUNTAIN  LIMESTONE.  Carbo- 
niferous limestone.  A  series  of  limestone 
strata  of  marine  origin,  usually  forming 
the  lowest  member  of  the  coal  measures. 

MOUNTAIN  SOAP.  A  mineral  sub- 
stance found  in  the  island  of  Skye,  and 
employed  in  crayon  painting. 

MOUNTAIN    TALLOW.    A  curious 


MUL 


MUR 


mineral  with  the  colour  and  feel  of  tallow, 
found  in  a  bog  on  the  borders  of  Loch 
Fyne  in  Scotland,  and  in  one  of  the 
Swedish  lakes.  It  differs  from  every 
known  class  of  bodies.  In  volatility  and 
combustibility  it  resembles  naphtha. 

MOYA.  A  term  applied  in  South 
America  to  mud  poured  out  from  vol- 
canoes during  eruptions. 

MUCIC  ACID.  An  acid  first  obtained 
from  sugar  of  milk,  and  hence  termed 
saccholactic ;  but  as  all  the  gums  appear 
to  yield  it,  and  the  principal  acid  in  the 
sugar  of  milk  is  the  oxalic,  it  is  now 
called  mucic. 

MUCUS.  One  of  the  primary  animai 
fluids,  perfectly  distinct  from  gelatin. 

MUDSTONE.  A  local  name  for  part 
of  the  Upper  Silurian  Rocks  of  Mr.  Mur- 
chison. 

MUFFLE.  A  small  earthen  oven, 
fixed  in  a  furnace,  and  used  in  cupella- 
tion,  and  other  processes  which  require 
the  access  of  air. 

MUGI'LIDjE  (mugil,  the  mullet).  The 
Mullet  tribe ;  a  family  of  acanthoptery- 
gious  fishes,  including  the  genera  mugil, 
tetragonurus,  and  atherina.  This  family 
is  included  in  the  cycloid  order  in  the 
system  of  Agassiz. 

MULLER'S  GLASS.  Another  name 
for  hyalite,  a  siliceous  substance  found  in 
fissures  in  vesicular  basalt  and  basaltic 
greenstone. 

MULTILATERAL  {multa  latera  ha- 
bens).  Having  many  sides;  as  applied 
to  a  geometrical  figure,  bounded  by  more 
than  four  straight  lines.     See  Polygon. 

MULTILOCULAR  {multos  looulos  ha- 
bens).  Having  many  loculi  or  chambers  ; 
a  term  applied  to  those  shells  which,  like 
the  nautilus  and  ammonite,  are  divided 
into  many  compartments. 

MULTINO'MIAL  {multa  nomina  ha- 
bens).  Having  many  terms ;  an  alge- 
braical expression  denoting  a  quantity 
which  consists  of  an  indefinite  number  of 
terms,  as  a  +  b  —  c  +  x  —  y,  &c.  Such 
a  quantity  is  also  termed  a  polynomial. 

MU'LTIPLE  {multiplex,  manifold).  A 
number  which  includes  another  a  cer- 
tain number  of  times  ;  thus  6  is  a  mul- 
tiple of  3  or  of  2 ;  18  is  a  multiple  of  9  or 
of  6.  Hence,  any  number  of  equal  mag- 
nitudes added  together  give  a  multiple 
of  any  one  of  them ;  thus  6  +  6  +  6,  or 
18,  is  a  multiple  of  6.     See  Submultiple. 

Least    common   multiple.    A  common 

multiple  of  two  or  more  numbers  is  one 

which  contains  each  of  them  ;   and,  of 

course,  the  least  such  number  is  their 

227 


least  common  multiple.  Thus  6,  12,  18, 
&c.  are  all  common  multiples  of  2  and  3  ; 
but  6  is  their  least  common  multiple ;  12, 
24,  36,  48,  &c.  are  all  common  multiples 
of  2,  3, 4,  6,  and  12 ;  but  12  is  their  leaf* 
common  multiple. 

MULTIPLE  POINTS.  In  Geometry, 
when  two  or  more  branches  of  a  curve 
pass  through  the  same  point,  this  is 
called  a  multiple  point ;  and  it  is  equally 
so  called,  whether  the  branches  touch  or 
cut  one  another. 

MULTIPLICAND.  That  factor,  num- 
ber, or  quantity  in  multiplication,  which 
is  to  be  repeated  the  number  of  times 
denoted  by  the  other  factor,  or  the  mul- 
tiplier. 

MULTIPLICATION.  The  arithme- 
tical method  of  finding  what  number 
would  result  from  adding  several  of  the 
same  numbers  together.  In  other  words, 
it  is  the  process  of  forming  a  multiple  : 
thus,  to  multiply  6  by  9,  is  to  repeat  6 
nine  times,  and  to  add  all  the  results 
together.  This  is  the  first  and  fundamen- 
tal meaning  of  multiplication.  The  num- 
bers multiplied  are  called  factors,  and 
the  result  is  called  the  product. 

MULTIPLIER.  An  instrument  in- 
vented simultaneously  by  Schweigger 
and  Poggendorf,  for  indicating  the  de- 
flecting influence  of  an  electric  current, 
and  applied  in  cases  in  which  the  current 
is  so  weak  as  to  require  its  conduction 
several  times  round  the  needle,  thus  re- 
peating or  multiplying  the  deflecting  in- 
fluence of  the  single  current. 

MU'LTI VALVE  {multos  valvas  ha- 
bens).  Having  many  valves,  as  the 
chitons  among  testaceous  mollusca. 

MURjE'NIDjE  {murcena,  a  lamprey). 
Anguillidce.  The  eel  tribe;  the  single 
family  of  Malacopterygious  or  soft-spined 
fishes,  belonging  to  the  section  Apodes, 
in  which  the  ventral  fins  are  wanting. 

MURAL  CIRCLE.  An  instrument 
for  measuring  the  distances  of  stars  from 
the  poles  or  the  Zenith.  It  consists  of  a 
circle  constructed  of  metal,  and  mechani- 
cally divided  into  equal  parts,  as  degrees, 
minutes,  &c.  A  tube  is  adjusted  to  the 
circle  so  as  to  revolve  together  with  it  on 
an  axis  concentric  with  the  circle.  The 
axis  is  let  into  a  wall,  and  rendered  ca- 
pable of  adjustment  both  in  a  vertical 
and  horizontal  direction ;  so  that,  like 
the  axis  of  the  transit,  it  can  be  main- 
tained in  the  exact  direction  of  the  east 
and  west  points  of  the  horizon,  the  plane 
of  the  circle  being  consequently  truly 
meridional. 

L6 


MUR 


MUS 


MU'RCHISONITE.  A  variety  of 
moonstone  or  felspar,  occurring  in  the 
new  red  sandstone,  in  the  neighbourhood 
of  Dawlish. 

%  MURE'XIDE  (murex,  a  molluscous 
animal  yielding  a  purple  dye).  A  beau- 
tiful purple  product  of  the  decomposition 
of  uric  acid,  first  described  by  Dr.  Prout 
as  purpurate  of  ammonia.  Murexan  is 
the  purpuric  acid  of  Prout. 

MU'RI  ACITE.  Anhydrous  sulphate  of 
lime,  also  called  anhydrite  and  cube-spar, 
occurring  crystalline,  fibrous,  granular, 
and  compact.  To  the  last  of  these  belong 
some  of  the  Italian  varieties  known  by 
the  names  of  bardiglio  and  bardiglione, 
as  also  the  singular  fibrous-compact 
variety  familiarly  called  tripe-stone  (pierre 
des  trippes),  from  the  salt  mines  of  Wie- 

MURIATE  or  HYDROCHLORATE. 
A  salt  formed  by  the  combination  of  mu- 
riatic or  hydrochloric  acid.  Metallic  muri- 
ates which  contain  an  excess  of  acid 
are  called  oxy-muriates ;  those  in  which 
there  is  a  deficiency  of  acid,  are  named 
sub-muriates. 

MURIA'TIC  ACID  {muria,  brine). 
Hydrochloric  acid.  An  acid  consisting 
of  chlorine  and  hydrogen,  and  contained 
in  great  abundance  in  sea-water,  in  com- 
bination with  soda  and  magnesia.  Oxy- 
genated muriatic  acid  is  another  name 
for  chlorine. 

MURICA'LCITE.  Another  name  for 
rhomb-spar,  a  mineral  consisting  of  the 
carbonates  of  lime  and  magnesia.  It  is 
also  called  bitter-spar. 

MURFCID^E.  The  Murexes  and 
Whelks  ;  a  family  of  carnivorous  Gaste- 
ropods,  having  the  respiratory  siphon  in 
general  very  much  developed,  and  its 
corresponding  canal  at  the  base  of  the 
shell  always  straight. 

MURICFIOS.  Murexes;  a  sub-family 
of  the  Muricidae,  named  from  the  typical 
genus  murex,  and  sometimes  called  rock- 
shells,  from  the  roughness  and  irregula- 
rity of  their  surface. 

MU'RIDjE  (mus,  a  mouse).  The  Rat 
tribe;  a  family  of  the  Rodentia,  con- 
taining the  smallest  and  the  most  nume- 
rous species  of  the  Mammalia. 

MU'RI DE  {muria,  brine).  The  name 
first  given  to  bromine,  from  its  being  an 
ingredient  of  sea- water. 

MU'RI  FORM  (murus,  a  wall,  forma, 
likeness).  Wall-like ;  a  term  applied  to 
the  tissue  constituting  the  medullary 
rays  in  plants,  from  its  presenting  an  ap- 
pearance similar  to  that  of  bricks  in  a  wall. 
228 


MU'SCA.  The  Fly;  a  modern  northern 
constellation,  consisting  of  six  stars, 
situated  between  Crux  and  the  South  Pole. 

MU'SCHELKALK  {muschel,  a  shell, 
kalk,  lime).  A  limestone,  belonging  to 
the  Upper  New  Red  Sandstone  group. 
Its  position  is  between  the  Magnesian 
Limestone  and  the  Lias.  This  formation 
has  not  yet  been  found  in  England,  and 
the  German  name  is  adopted  by  English 
geologists. 

MUSCI.  The  Moss  tribe  of  Acotyle- 
donous  plants.  Cellular,  Jlowerless  plants, 
with  leaves  imbricated,  entire,  or  ser- 
rated ;  reproductive  organs  either  axil- 
lary bodies  containing  spherical  or  oval 
particles,  emitted  on  the  application  of 
water,  or  thecce,  seated  on  a  seta  or 
stalk. 

MUSCICA'PID^E  (muscicapa,  the  fly- 
catcher). MyiotherincB.  The  Fly-catchers; 
a  family  of  the  Insessores,  or  Perching 
birds,  characterized  by  the  peculiar  form 
of  the  bill,  with  the  strong  bristles  at  its 
base,  and  by  the  small  size  of  the  feet. 
See  Dentirostres. 

MUSCID^  (musca,  a  fly).  The  Fly 
tribe ;  a  family  of  Dipterous  insects,  be- 
longing to  the  sub-section  Athericera, 
readily  distinguished  by  their  strong  gene- 
ral resemblance  one  to  another.  Their 
larvae  are  known  as  maggots. 

MUSCOVY  GLASS.  Another  name 
for  mica,  most  of  the  commercial  article 
being  brought  from  Siberia,  where  it  is 
used  for  window-glass. 

MUSCULAR  IMPRESSIONS.  A 
term  applied  to  those  indented  marks  in 
acephalous  bivalves,  which  indicate  the 
insertion  of  those  muscles  by  which  the 
animal  is  attached  to  its  shell.  Of  these 
there  are  three  principal  varieties  ? — 

1.  The  lateral  impressions,  which  de- 
note that  the  animal  has  two  adductor 
muscles,  as  in  unio  cardium,  and  all  the 
most  typical  bivalves. 

2.  The  central  impression,  which  de- 
notes the  presence  of  only  one  adductor 
muscle,  which  is  generally  in  the  middle 
of  the  shell,  as  in  the  oyster. 

3.  The  pallial  impression,  which  oc- 
curs in  all  these  shells,  and  is  indicated 
by  a  depressed  line,  often  sinuated,  run- 
ning parallel  with  the  ventral  margin. 

MUSICAL  SOUND.  A  succession  of 
sounds  which  follow  one  another  with 
such  regularity  as  to  produce  the  impres- 
sion of  a  single  sound. 

MUSOPHA'GIDvE.  The  Plantain- 
eaters  ;  a  family  of  birds  intermediate 
between  the  Finches  and  the  Hornbills, 


MYR 


M  Y  T 


the  Musophaga  being  the  most  conspi- 
cuous of  the  group. 

MUSSEL  BAND.  The  black  shale 
of  coal  mines,  containing  embedded 
mussel-shells. 

MUSSITE.  A  pale  green  mineral 
from  Mussa,  in  Piedmont,  consisting 
of  a  variety  of  augite. 

MUSTE'LID^E  {mustela,  a  weasel). 
The  Weasel  tribe;  a  family  of  carni- 
vorous vertebrata,  which  are  mostly 
semi-plantigrade,  a  portion  of  the  sole 
touching  the  ground.  These  animals, 
owing  to  the  length  of  theif  bodies,  and 
the  shortness  of  their  limbs,  are  enabled 
to  insinuate  themselves  into  small  ori- 
fices, and  are  hence  called  vermiform. 

MYADiE.  Gaping  Bivalves ;  a  family 
of  the  macrotrachian  bivalves ;  named 
from  the  genus  mya,  and  having  the 
valves  more  or  less  gaping  at  one  or  both 
extremities. 

MYCE'LIA  (/divan?,  a  mushroom).  The 
rudiments  of  fungi,  or  the  matter  from 
which  fungi  are  produced. 
M  YELENCE'PH  ALA  (/m/cAop,  marrow, 
hyKecpaXov,  the  brain).  A  term  applied  by 
Owen  to  the  grand  primary  division  Ver- 
tebrata of  the  animal  kingdom,  compris- 
ing animals  which  possess  a  brain  and 
spinal  marrow.  These  are  the  Spini- 
cerebrata  of  Grant. 

MYELONEU'RA  (^veXo?,  marrow, 
vevpov,  nerve).  The  name  given  by  Ru- 
dolphi  to  a  group  of  animals  correspond- 
ing with  the  Articulata  of  Cuvier,  which 
have  a  ganglionic  nervous  system,  form- 
ing a  cord  considered  analogous  to  the 
spinal  marrow  of  the  Vertebrata. 

MY'IOTHE'RIN^  [pmd,  a  fly,  flrjpdw, 
to  chase).  Fly-chasers  ;  a  family  of  the 
Insessores  or  Perching  birds,  or  the  Ex- 
curtrices  of  Macgillivray.  The  terra  is 
synonymous  with  Muscicapidae. 

MYRIA'PODA  (/jivpior,  innumerable, 
Trow?,  irodoc,  a  foot).  The  first  class  of 
the  Diplo-gangliata,  or  Entomo'ida,  com- 
prising animals  with  articulated  bodies, 
all  the  segments  of  the  trunk  being  pro- 
vided each  with  one  or  two  pairs  of 
jointed  ambulatory  feet.  They  are  di- 
vided into  the  two  following  orders  by 
the  differences  of  their  jaws  and  feet : — 

1.  Ctylognatha,  or  those  which  have 
solid  cylindrical  segments,  antennae  with 
seven  joints,  two  strong  mandibles  with- 


out palpi,  and  very  short  feet  terminated 
by  simple  ungues,  as  in  the  iulus, 

2.  Chilopoda,  or  those  in  which  the 
segments  are  more  soft  and  depressed, 
and  each  furnished  with  a  single  pair  of 
feet ;  the  antennae  have  more  than  thir- 
teen joints,  and  the  mouth  is  furnished 
with  palpigerous  mandibles,  and  with  an 
upper  and  lower  lip,  as  in  the  scolopendra 
morsitans. 

MY'RICIN.  The  ingredient  of  wax 
which  remains  after  digestion  with  alco- 
hol. 

MYRISTICA'CE^E.  The  Nutmeg  tribe 
of  dicotyledonous  plants.  Trees  with 
leaves  alternate  ;  flowers  dioecious,  with 
no  trace  of  a  second  sex ;  fruit  baccate, 
dehiscent,  2-valved;  seed  nut-like,  en- 
veloped in  a  many-parted  arillus. 

MY'RMELEO'NIDjE  (m<''PMi?,  an  ant, 
\ca>f,  a  lion).  A  family  of  Neuropterous 
insects,  named  from  the  typical  genus 
myrmeleon,  the  larvae  of  which,  from 
their  peculiar  habits,  have  acquired  the 
name  of  ant-lions. 

MY'RMOTHERINjE  (miVmh?,  an  ant, 
0ripdu>,  to  chase).  Myrmotherine  birds, 
or  Ant-catchers ;  a  family  of  the  Canta- 
trices of  Macgillivray,  distinguished  from 
the  Thrushes  chiefly  by  their  shortened 
form.  The  only  British  species  is  the 
Cinclus  or  Dipper. 

MYRO'NIC  ACID  (n^pov,  an  odorous 
oil).  A  bitter  acid  procured  from  black 
mustard  seeds. 

MYRTACEiE.  The  Myrtle  tribe  of 
dicotyledonous  plants.  Trees  or  shrubs 
with  leaves  opposite,  entire,  and  marked 
with  transparent  dots ;  flowers  polype- 
talous  ;  stamens  perigynous  ;  carpella 
concrete;  inferior  ovarium  with  several 
cells. 

M YSTACI'NEjE  (M«5o-raf,  moustache). 
A  family  of  the  Infusoria,  including 
those  which  have  superficial  cilia  dis- 
posed in  groups. 

MYTILA'CEjE.  The  Mussel  tribe; 
an  order  of  the  conchiferous  Mollusca, 
named  from  the  mytilus,  in  which  the 
mantle  remains  open  in  front  (at  the  end 
where  the  mouth  is  situated),  and  closed 
behind,  an  aperture  being  left  for  the 
egress  of  the  fluid.  They  have  a  foot 
sufficiently  strong  for  crawling,  and  com- 
monly affix  themselves  by  a  byssus. 


229 


NAP 


NAT 


N 


NA'CREOUS  {nacre,  pearl).  A  term 
applied  to  a  shell  which  has  a  pearly 
lustre  and  reflects  iridescent  light. 

NACR1TE.  The  name  given  by 
Jameson  to  talcite,  or  the  earthy  talc  of 
Werner;  a  very  rare  mineral,  occurring 
in  veins,  with  sparry  ironstone  and  ga- 
lena, in  the  mining  district  of  Freyberg. 

NADIR.  An  Arabic  term  denoting 
that  point  of  the  sphere  of  the  heavens 
which  is  diametrically  opposite  to  the 
zenith,  and  vertically  beneath  the  feet  of 
a  spectator.  The  term  evidently  cor- 
responds with  the  German  nieder  (down). 
The  zenith  and  the  nadir  are  the  two 
poles  of  the  horizon.     See  Zenith. 

NADLESTEIN.  Another  name  for 
rutile,  an  ore  of  titanium. 

NAGYAG  ORE.  Foliated  tellurium, 
a  mineral  consisting  of  tellurium  and 
lead. 

NAPADES.  A  family  of  fresh-water 
conchiferous  mollusks,  comprising  the 
genera  unio,  hyria,  anodon,  and  iridina, 
occurring  abundantly  in  the  North  Ame- 
rican rivers. 

NAKED  SEEDS.  An  incorrect  term, 
applied  by  Linnaean  botanists  to  the 
small  seed-like  fruits  of  the  Labiatae, 
Boraginaceae,  and  other  families  of  plants. 
Seeds  entirely  destitute  of  a  pericarp 
occur  only  in  Coniferae,  Cycadaceae,  and 
Gnetaceae. 

NAKER  FELDSPAR.  A  species  of 
feldspar,  also  called  adularia,  and  found 
principally  on  Mount  St.  Gothard,  but 
not  in  the  valley  of  Adula,  from  which 
the  latter  name  is  derived.  The  fine 
variety  from  Ceylon,  when  cut  en  carbo- 
chon,  is  called  moonstone ;  and  a  yellow 
naker  feldspar  with  reddish  dots  has  ob- 
tained the  name  of  sunstone,  which  is 
also  sometimes  given  to  the  beautiful 
avanturino  variety  of  common  feldspar. 

NANCE'IC  ACID.  An  acid  found  in 
many  acescent  vegetable  substances,  and 
named  by  Braconnot  from  the  town  of 
Nancy 

NAPHTHA.  A  highly  inflammable, 
thin,  colourless  oil,  which  issues  from 
the  white,  yellow,  or  black  clays  in  Persia 
and  Media,  and  of  which  there  are 
springs  in  many  countries,  particularly 
in  volcanic  districts.  Black  Naphtha  is 
230 


a  common  name  for  petroleum,  or  rock 
oil. 

NAPHTHALINE.  A  greyish  white 
substance  found  during  the  rectification 
of  the  petroleum  of  the  coal  gas  works, 
incrusting  the  pipes.  Mineral  or  resin- 
ous Caphthaline  has  been  found  native 
in  a  layer  of  lignite,  in  the  coal  forma- 
tion of  Uznach. 

NAPIER'S  RODS,  or  BONES.  A 
contrivance  for  facilitating  the  mecha- 
nical performance  of  multiplication  and 
division.  The  invention  has  been  super- 
seded by  the  discovery  of  logarithms. 

NAPLES  YELLOW.  A  pigment  pre- 
pared by  calcining  lead  with  antimony 
and  potash  in  a  reverberatory  furnace, 
formerly  made  at  Naples. 

NAPO'LEON.  A  name  given  to  the 
constellation  Orion. 

NASCENT  STATE  (nascor,  to  be 
born).  A  term  applied  to  the  state  of 
gases,  at  the  moment  of  their  generation, 
before  they  have  acquired  the  repulsive 
power. 

NASSFNjE.  A  sub-family  of  the  Mu- 
ricidce,  named  from  the  typical  genus 
nassa. 

NATATO'RES  (nato,  to  swim).  An 
order  of  Birds,  easily  distinguished  by 
their  oar-like  feet,  adapted  to  swimming. 
They  include  the  duck,  the  gull,  the 
pelican,  the  diver,  and  the  penguin.  In 
the  first  three,  the  length  of  the  wings 
adapts  them  for  flight ;  in  the  last  two, 
the  wings  are  short,  and  serve  only  as 
fins. 

NATFCIDjE.  The  Nerits;  a  family 
of  the  Phytophagous  Gasteropods,  in 
which  the  spire  is  very  small,  but  the 
pillar  is  always  thick ;  the  exposed  part, 
or  inner  lip,  is  often  very  broad;  the 
animal  is  slug-shaped. 

NATICFNjE.  Sea-snails  ;  a  sub- 
family of  the  Naticidce,  named  from  the 
genus  natica,  and  characterized  by  a 
globose  shell ;  the  inner  lip  is  smooth, 
not  depressed. 

NATRIUM.  A  term  formerly  used 
to  designate  sodium.  Natron  is  native 
carbonate  of  soda,  found  in  mineral 
seams  or  crusts,  and  hence  called  mineral 
alkali. 

NA'TROLITE.       A    sub-species    of 


N  A  V 


NEC 


prismatic  zeolite  or  mesotype,  occurring 
in  chalk-stone  porphyry  in  Wurtemherg 
and  Bohemia,  &c. 

NATRON.  Native  carbonate  of  soda. 
There  are  two  kinds,  the  common  and 
the  radiated.     See  Natrium. 

NATURAL.    A  character  in  music, 

marked  fa,  employed  to  make  a  sharp 
note  a  semitone  lower,  and  a  flat  note  a 
semitone  higher;  or,  in  other  words,  to 
restore  to  the  scale  of  the  natural  key  of 
C  any  note  which  had  been  made  flat  or 
sharp. 

NATURAL  ORDERS  OF  PLANTS. 
That  arrangement  of  plants  in  which 
groups  are  formed  by  the  association 
together  of  those  genera,  which  have  the 
greatest  resemblance  one  to  another  in 
all  their  characters  taken  together.  Na- 
ture has  pointed  out  this  plan  in  several 
well-marked  groups,  and  it  is  the  object 
of  botanists  to  extend  the  principle  to  all 
the  individuals  of  the  vegetable  kingdom. 

NATURAL  PHILOSOPHY.  The 
science  which  teaches  the  nature  and 
properties  of  matter,  the  motions  of 
bodies,  their  connexions  with,  and  their 
influence  upon,  one  another.  The  sub- 
ject is  distinguished  into  the  two  branches 
of  Mechanical  Philosophy  and  Chemistry. 

NAUCUM.  An  old  Latin  term  ap- 
plied by  botanists  to  the  exterior  coat  of 
the  drupe ;  it  is  soft  and  fleshy,  and 
separable  from  the  interior,  hard,  and 
bony  coat,  which  is  called  the  endocar- 
pium,  or  stone.  Gsertner  applied  the 
term  nauca  to  seeds  which  have  a  very 
large  hilum,  as  that  of  the  horse-chest- 
nut. 

NAUTICAL  DISTANCE.  In  navi- 
gation, this  term  denotes  the  line  which 
makes  with  the  meridian  lines  the  angle 
called  the  course.  In  other  words,  the 
rhumb  line  intercepted  between  any  two 
places  through  which  the  rhumb  line 
passes,  is  their  nautical  distance. 

NAUTI'LIDjE.  The  sixth  family  of 
Lamarck's  polythalamous  cephalopods, 
named  from  the  genus  nautilus.  It  forms 
the  fifth  family  of  the  Polythalamaceae 
of  De  Blainville. 

NAU'TILITES.  Fossil  shells,  analo- 
gous to  the  nautilus,  found  in  various 
strata,  from  the  oldest  limestones  and 
sandstones  of  the  Silurian  system,  to 
those  covering  the  chalk. 

NAVIGATION  (navigo,  to  manage  a 

ship).      The  science  which  teaches  the 

mariner  how  to  conduct  his  ship  from 

one  port  or  place  to  any  other.    It  con- 

231 


sists  in  the  practical  application  of  a 
branch  of  mathematics,  and  of  a  branch 
of  astronomy,  which  owes  its  name  to 
this  application. 

NEACOMIAN  SYSTEM.  A  geolo- 
gical formation  comprising  the  green 
sand  system,  and  divided  into  the  lower 
green  sand — gait,  or  Cambridge  clay — and 
upper  green  sand.  The  last  two  are  con- 
sidered by  some  writers  as  a  part  of  the 
Cretaceous  system. 

NEBULA  (dim.  of  nubes,  a  cloud).  A 
dusky  speck  in  the  heavens,  exhibiting 
a  dim  and  cloudy  light,  scarcely  visible 
to  the  naked  eye,  and  supposed  to  con- 
sist of  a  cluster  of  stars  closely  connected 
in  the  most  beautiful  arrangement,  and 
at  such  an  inconceivable  distance  from 
our  system,  that  each  of  them  is  con- 
jectured to  be  composed  of  several  thou- 
sand distinct  luminous  bodies.  Nebulae 
have  been  distinguished  by  Sir  W. 
Herschel  into — 

1.  Clusters  of  stars,  in  which  the  stars 
are  clearly  distinguishable ;  and  these, 
again,  into  globular  and  irregular  clusters. 

2.  Resolvible  nebulae,  or  such  as  excite 
a  suspicion  that  they  consist  of  stars,  and 
which  any  increase  of  the  optical  powers 
of  the  telescope  may  be  expected  to  re- 
solve into  distinct  stars. 

3.  Nebula,  properly  so  called,  in  which 
there  is  no  appearance  whatever  of  stars  ; 
which,  again,  have  been  subdivided  into 
subordinate  classes,  according  to  their 
brightness  and  size. 

4.  Planetary  nebulce,  having,  as  their 
name  imports,  exactly  the  appearance  of 
planets,  and,  whatever  be  their  nature, 
of  enormous  magnitude. 

5.  Stellar  nebula,  of  a  round  or  oval 
figure,  increasing  more  or  less  in  density 
towards  the  central  point :  they  differ 
extremely,  however,  in  this  respect,  the 
condensation  in  some  being  slight  and 
gradual,  in  others  great  and  sudden,  so 
as  to  represent  a  star  with  a  slight  burr 
round  it. 

6.  Nebulous  stars,  presenting  the  ap- 
pearance of  sharp  and  brilliant  stars  sur- 
rounded by  a  perfectly  circular  disc,  or 
atmosphere  of  faint  light,  in  some  cases 
dying  away  on  all  sides  by  insensible 
gradations  ;  in  others,  almost  suddenly 
terminated. 

NECESSARY.  "  This  word  is  used 
as  the  contrary  to  '  impossible '  in  all  its 
senses,  and  is,  of  course,  liable  to  a  cor- 
responding ambiguity.  Thus,  it  is 
4  mathematically  necessary '  that  two 
sides  of  a  triangle  should  be  greater  than 


NEM 


NEU 


the  third ;  there  is  a  '  physical  necessity ' 
for  the  fall  of  a  stone ;  and  a  '  moral 
necessity '  that  beings  of  a  certain  cha- 
racter should  act,  when  left  perfectly 
free,  conformably  to  that  character ;  i.  e. 
we  are  sure  they  will  act  so ;  though,  of 
course,  it  is  in  their  power  to  act  other- 
wise." The  ambiguity  consists  in  con- 
founding the  second  and  the  third  kinds 
of  necessity,  and  thu3  finding  an  excuse 
for  immoral  conduct. —  Whately. 

NECESSARY  MATTER.  In  Logic, 
the  necessary  matter  of  a  proposition 
denotes  the  essential  or  invariable  agree- 
ment of  its  terms.  In  necessary  matter, 
all  affirmatives  are  true,  and  negatives 
false ;  in  impossible  matter,  vice  versd ; 
in  contingent  matter,  all  universals  are 
false,  and  particulars  true. 

NE'CROMITE.  A  white  mineral 
found  near  Baltimore,  in  small  masses, 
in  limestone. 

NE'CTARY.  That  part  of  a  flower 
which  secretes  nectar  or  honey.  The 
term  has  been  vaguely  applied  to  several 
parts  which  have  no  such  function. 

NEEDLE-ORE.  A  triple  sulphuret 
of  bismuth,  lead,  and  copper,  also  called 
acicular  bismuth  glance. 

NEEDLE-STONE.  A  zeolitic  sub- 
stance of  a  grej  ish-white  colour,  found  in 
secondary  trap  rocks  near  Old  Kilpatrick 
in  Scotland. 

NEGATION,  CONVERSION  BY.  In 
logic,  a  mode  of  illative  conversion,  com- 
monly called  by  contra-position.  Thus  it 
may  be  said—"  Every  poet  is  a  man  of 
genius ;  therefore,  he  who  is  not  a  man 
of  genius  is  not  a  poet ; "  for  it  is  the 
same  thing  to  affirm  some  attribute  of 
the  subject,  or  to  deny  the  absence  of  that 
attribute. 

NEGATIVE  QUANTITY.  In  alge- 
bra, any  quantity  to  which  the  sign  —  is 
prefixed,  is  called  a  negative  quantity. 
The  explanation  of  such  a  quantity  is  a 
difficult  matter.  It  is,  however,  usually 
defined,  either  as  a  quantity  less  than 
nothing,  or  as  a  quantity  of  the  same 
nature  as  a  positive  quantity,  but  ( taken 
in  a  contrary  sense  or  in  an  opposite 
direction.     See  Quantity. 

NEGATIVE  TERM.  In  logic,  a  ne- 
gative term  denotes  that  a  certain  view 
is  not  and  could  not  be  formed  of  a  par- 
ticular object,  as  a  "dumb  statue,"  a 
"lifeless  carcass."    Compare  Privative. 

NEMATOI'DEA     (vrina,  vtifiaTor,    a 

thread,  ei<5or,  likeness).     Round  worms ; 

an  order  of  the  Entozoa,  which  have  a 

long,    cylindrical,    and    often    filiform, 

232 


naked,  inarticulated  body,  traversed  by 
a  straight  alimentary  canal  open  at  both 
ends.  These  are  the  cavitary  intestinal 
worms  of  Cuvier,  the  stcrelmintha  of 
Owen. 

NE'MATONEU'RA  (i^Ma,  n^mtm 
a  thread,  vevpov,  a  nerve).  A  term  ap- 
plied by  Owen  to  a  division  of  the 
Radiata  of  Cuvier,  in  which  the  nervous 
matter  is  distinctly  aggregated  into  fila- 
ments, and  in  some  cases  nuclei  of  rudi- 
mentary nervous  centres  have  been 
noticed. 

NEMO'CERA  (tffcuu  a  thread,  icepos, 
a  horn).  A  section  of  Dipterous  insects, 
characterized  by  their  long  filiform  an- 
tennae, composed  of  more  than  six  joints. 

NE'PHELINE  (vecpeXr,,  a  cloud). 
Sommite.  Rhomboidal  feldspar,  occurring 
at  Monte  Somma,  near  Naples,  in  granu- 
lar limestone,  and  in  the  lava  of  Capo  di 
Bove,  near  Rome.  In  nitric  acid  its 
transparent  fragments  become  cloudy. 

NEPHRITE  (i/e0p6P,  a  kidney).  Jade. 
A  mineral  occurring  in  gneiss  and  gra- 
nite. It  comprises  the  common  variety 
and  axestone.  The  South  America  va- 
riety is  called  Amazonian  stone,  from 
its  locality.  It  was  formerly  used,  as  an 
amulet,  in  nephritic  complaints. 

NE'PIDjE.  A  family  of  the  Hydro- 
corisa,  or  Water  Bugs,  resembling  the 
Notonectidas,  or  boat-flies,  in  structure 
and  in  habits,  but  endowed  with  slower 
powers  of  motion. 

NEPTU'NIAN  THEORY.  A  geolo- 
gical theory  of  Werner,  which  refers  the 
formation  of  rocks  and  strata  to  an  aque- 
ous origin. 

NEREIDiE.  A  common  name  for  a 
highly  organized  order  of  Annellida, taken 
from  the  Linnsean  generic  name  Nereis, 
which  is  almost  equivalent  to  the  ordinal 
designation  Errantes  of  Milne  Edwards. 
These  are  the  dorsibranchiata  of  Cuvier, 
the  sea-centipedes  and  sea-mice  of  popu- 
lar language. 

NERPTIN.E.  A  sub-family  of  the 
Naticidce,  or  Nerits,  named  from  the 
genus  neritina ;  in  these  shells  the  spire 
is  often  nearly  or  quite  obsolete. 

NE'RVURES  {nervus,  a  sinew).  The 
delicate  frame-work  of  the  membranous 
wings  of  insects. 

NEURO'PTERA  {vevpov,  a  nerve, 
•mepov,  a  wing).  An  order  of  insects 
furnished  with  four  membranous  wings, 
which  are  naked  and  reticulated  with 
ramified  trachea?.  It  includes  the  dra- 
gon-flies, may-flies,  ant-lions,  white 
ants,  &c. 


NIM 


NOB 


NEUTRAL  SALTS.  Formerly,  salts 
in  which  the  base  was  perfectly  saturated 
with  the  alkali,  thus  possessing  neither 
an  acid  nor  an  alkaline  character.  The 
term  now  denotes  those  compounds, 
which  are  composed  of  one  equivalent 
of  each  of  their  constituents,  without 
reference  to  their  taste,  or  to  their  action 
on  coloured  tests. 

NEUTRALIZATION.  A  term  gene- 
rally applied  to  the  decomposition  of  the 
alkaline  carbonates,  by  the  addition  of 
some  acid  more  powerful  than  the  car- 
bonic acid,  which  is  consequently  ex- 
pelled from  the  alkaline  bases  with  effer- 
vescence. 

NEW  RED  SANDSTONE.  A  forma- 
tion consisting  chiefly  of  sandy  and 
argillaceous  strata,  the  predominant  co- 
lour of  which  is  brick-red,  though  it 
contains  portions  which  are  of  a  greenish- 
grey.  The  striped  and  spotted  appear- 
ance of  this  series  has  caused  it  to  be 
sometimes  termed  variegated  sandstone. 
This  formation  has  been  divided  into  the 
Upper  New  Red,  in  which  Muschelkalk 
is  included,  and  the  Lower  New  Red, 
of  which  the  Magnesian  Limestone  is  a 
member. 

NICKEL.  A  metal  of  a  colour  inter- 
mediate between  those  of  silver  and  of 
,  tin,  and  commonly  obtained  from  its 
sulphuret,  the  kupfernickel  of  the  Ger- 
mans, which  is  generally  mixed  also 
with  arsenic,  iron,  and  cobalt.  The  sul- 
phuret was  formerly  called  capillary  iron 
pyrites,  and  afterwards  considered  as 
native  nickel,  till  its  real  composition 
was  determined  by  Arfvedson. 

NIDAME'NTAL  {nidus,  a  nest).  Re- 
lating to  the  protection  of  the  egg  and 
young,  especially  applied  to  the  organs 
which  secrete  the  materials  of  which 
many  animals  construct  their  nests. 

NIDITE'LiE  (nidus,  a  nest,  tela,  a 
web).  A  family  of  Spiders,  which  weave 
a  nest,  from  which  issue  threads  to  en- 
trap their  prey. 

NIGRINE.  An  ore  of  titanium,  con- 
sisting of  this  metal  and  iron. 

NFHIL  ALBUM.  A  former  name  of 
the  flowers  or  white  oxide  of  zinc.  Lana 
philosophica  was  an  equally  curious  de- 
signation of  the  same  substance. 

NIMBUS,  or  CUMULO-CIRRO- 
STRATUS.  The  rain-cloud;  a  compo- 
site modification  of  clouds,  resulting 
from  increase  of  density  and  deepening  of 
shade  in  the  cumulo-stratus,  indicating 
a  change  of  structure,  which  is  always 
followed  by  the  fall  of  rain.  All  the 
233 


other  forms  of  cloud  may  increase  so  as 
to  obscure  the  sky,  and  dissolve  without 
falling  in  rain;  but  the  nimbus,  once 
formed,  is  always  followed  by  rain  or 
snow. 

NINTH.  A  dissonant  interval  in 
Music,  retarding  the  eighth  and  resolv- 
ible  into  either  the  sixth  or  the  third. 
The  major  ninth  consists  of  six  tones 
and  two  semitones ;  the  minor  ninth,  of 
five  tones  and  three  semitones. 

NITRATES.  Compounds  of  nitric 
acid  with  the  salifiable  bases. 

NITRE.  Saltpetre,  or  nitrate  of  pot- 
ash. When  fused,  and  poured  into 
moulds,  it  is  called  sal  prunella,  or  crys- 
tal mineral;  when  mixed  with  charcoal, 
and  burnt,  the  residuum  was  formerly 
called  clyssus  of  nitre ;  mixed  with  car- 
bonate of  potash  and  sulphur,  in  a  warm 
mortar,  it  forms  the  fulminating  powder  ; 
mixed  with  sulphur  and  charcoal,  it 
forms  gunpowder ;  and  when  mixed  with 
sulphur  and  fine  saw-dust,  it  constitutes 
the  powder  of  fusion. 

NITRIC  ACID.  A  constituent  of 
nitre  or  saltpetre,  existing  only  in  com- 
bination, and  named,  from  its  corrosive 
properties,  aquafortis. 

NITROGEN  {vhpov,  nitre,  ^wda,  to 
produce ;  so  called  from  its  being  a  gene- 
rator of  nitre).  Azote.  An  elementary 
principle,  constituting  four-fifths  of  the 
volume  of  atmospheric  air.  It  was 
formerly  called  mephitic  air,  and,  by 
Priestley,  phlogisticated  air. 

1.  Nitrous  Oxide.  Formerly  called  by 
Priestley,  who  discovered  it,  dephlogisti- 
cated  nitrous  air;  but  more  properly, 
protoxide  of  nitrogen.  Its  common  name 
is  laughing  gas. 

2.  Nitric  Oxide,  or  nitrous  gas.  For- 
merly called  nitrous  air ;  but,  more  pro- 
perly, deutoxide  of  nitrogen.  When 
mixed  with  atmospheric  air,  nitrous  acid 
vapours  are  produced,  of  a  red  or  orange 
brown  colour. 

3.  Nitrous  Acid.  Formerly  called 
fuming  nitrous  acid ;  an  acid  of  un- 
certain constitution,  termed  hyponitrous 
by  Turner. 

4.  Peroxide  of  Nitrogen.  A  compound 
forming  the  principal  part  of  the  nitrous 
acid  vapours  above  mentioned.  This 
is  the  nitrous  acid  of  Turner. 

NITRUM  FLAM  MANS.  Nitrate  of 
ammonia,  so  named  from  its  property  of 
exploding,  and  undergoing  total  decom- 
position at  the  temperature  of  600°. 

NOBILl'S  FIGURES.  The  name 
given  to  an  electro-chemical  phenomenon, 


NOD 


NON 


discovered  by  Nobili.  If  a  feeble  current 
be  applied  to  polished  plates  of  platinum, 
steel,  and  silver,  by  using  them  as  elec- 
trodes, and  immersing  them  in  an  elec- 
trolytic fluid,  certain  figures  will  be  visi- 
ble, generally  in  the  form  of  concentric 
circles  whose  centre  is  exactly  opposite  to 
the  point  of  the  wire,  very  much  resem- 
bling Newton's  Prismatic  Rings,  and  so 
firmly  fixed,  that  they  cannot  be  removed 
even  by  washing  the  metal  with  nitric  acid. 

NOCTILIONI'NjE.  A  family  of  in- 
sectivorous Cheiroptera,  which  are  desti- 
tute of  nasal  appendages,  and  are  almost 
exclusively  confined  to  tropical  coun- 
tries. 

NOCTU'RNA  (noctumus,  nightly).  A 
designation  of  the  true  moths,  a  tribe  of 
Lepidopterous  insects,  the  greater  part 
of  which  fly  by  night. 

NODAL  LINES.  A  term  employed 
in  speaking  of  the  undulations  of  solid 
bodies.  Thus,  in  the  movements  of 
elastic  planes,  complete  rows  of  points, 
called  nodal  lines,  will  be  formed  which 
do  not  participate  in  the  movements  of 
the  planes,  but  are  in  a  state  of  rest. 
These  nodal  lines  are  produced  by  the 
continuous  succession  of  nodal  points,  in 
the  strings  of  which  the  plane  is  supposed 
to  consist.  They  run  in  various  direc- 
tions across  the  plane,  dividing  it  into 
numerous  vibrating  portions,  the  con- 
tiguous portions  invariably  moving  in 
contrary  directions.  The  nodal  lines 
form  peculiar  figures,  called,  after  their 
discoverer,  Chladni's  Sonorous  Figures. 

NODAL  POINTS.  When  a  tense 
cord  is  thrown  into  vibration,  it  assumes 
throughout  its  entire  length  the  form  of 
elevations  and  depressions  impinging  on 
oae  another,  the  elevation  passing  into 
the  form  of  a  depression,  and  vice  versa. 
The  point  which  bounds  an  elevation  and 
a  depression,  continuing  at  rest  during 
the  vibration,  is  called  a  nodal  point. 

NODE  {nodus,  a  knot).  In  astronomy, 
the  nodes  are  the  points  where  the  orbit 
of  a  planet  cuts  the  plane  of  the  ecliptic. 
The  node  whence  the  planet  rises  to- 
wards the  north  above  the  plane  of  the 
ecliptic  is  the  ascending  node,  that  whence 
it  descends  towards  the  south  is  the  de- 
scending node;  the  line  joining  the  two 
is  called  the  line  of  the  nodes.  Generally, 
the  point  in  which  one  orbit  cuts  another 
is  called  the  node  of  the  first  upon  the 
second. 

NODE  {in  Botany).     This  term  signi- 
fies the    thickened    part    of   a  stem    or 
branch  from  which  a  leaf  is  developed. 
234 


The  space  between  two  nodes  is  termed 
an  internode. 

NO'DULE  (dim.  of  nodus,  a  node). 
A  little  node  ;  a  small  woody  body  found 
in  the  bark  of  the  beech  and  some  other 
trees,  and  formed  of  concentric  layers 
of  wood  arranged  around  a  central  nu- 
cleus. Dutrochet  terms  it  an  embryo- 
bud. 

NODULE  (in  Geologij).  A  rounded 
irregular-shaped  lump  or  mass,  varying 
in  size,  and  embedded  in  a  stratified  or  a 
massive  rock. 

NOMENCLATURE.  A  general  de- 
signation of  the  terms  employed  in  any 
science  or  art. 

NOMINAL  DEFINITION.  In  logic, 
a  definition  which  explains  only  the 
meaning  of  the  term  defined,  and  nothing 
more  of  the  nature  of  the  thing  signified 
by  that  term  than  is  implied  by  the  term 
itself  to  every  one  who  understands  the 
meaning  of  it.     See  Real  Definition. 

NOMINALISTS  and  REALISTS. 
Two  scholastic  sects  of  the  11th  century, 
the  former  of  which  affirmed,  according 
to  the  Platonic  doctrine,  that  names  or 
general  terms  have,  apart  from  the  mere 
conception  of  them  by  the  understand" 
ing,  an  actual  and  eternal  existence,  and 
are  the  models  of  all  created  beings; 
while  the  latter  maintained,  according  to 
the  doctrine  of  Aristotle,  that  these 
names  were  eternally  united  to  matter, 
and  have  no  existence  as  unconnected 
with  it.     See  Idea. 

NO'MINATIVE  CASE  (nomino,  to 
name).  The  naming  case;  the  case 
which  precedes  the  verb,  and  designates 
its  subject  absolutely,  without  relation 
to  any  other  subject.  A  noun  in  the 
nominative  case  (casus  rectus)  was  con- 
sidered by  ancient  grammarians  as  a 
line  perpendicular ;  and  in  the  other 
cases  (casus  obliqui)  as  gradually  decli- 
ning or  falling  from  the  perpendicular. 
To  decline  a  noun,  is,  therefore,  to  make 
it  pass  through  these  cases  or  fallings, 
and  the  representation  of  them  is  called 
a  declension. 

NON  CAUSA  PRO  CAUSA.  A  logi- 
cal fallacy  in  which  the  premiss  (whether 
the  expressed  or  the  suppressed  one)  is 
either  proved  false,  or  has  no  sufficient 
claim  to  be  received  as  true. 

NON-CONDUCTORS.  Substances 
which  carry  off  free  electricity  slowly 
when  touched  by  an  electrified  body  ;  or, 
if  their  condition  of  electrical  indiffer- 
ence is  disturbed  at  any  one  point,  they 
become  electrical  at  that  point  only ;  and 


NOR 


NOT 


if  their  whole  surface  he  excited,  and 
they  are  then  touched  by  some  conductor 
connected  with  the  ground,  they  part 
with  their  free  electricity  only  at  the 
point  of  contact.  Their  characteristic  is, 
that  they  retain  free  electricity  for  a 
length  of  time,  and  that  they  check  its 
motion. 

NON-ELECTRICS.  It  was  formerly 
thought  that  none  but  the  non-conductors 
could  be  electrically  excited,  and  that  no 
other  bodies  possessed  electricity  ;  hence 
the  name  of  electrics  was  given  to  the 
former,  and  that  of  non-electrics  to  the 
latter  class  of  substauces. 

NONAGE'SIMAL  DEGREE.  The 
highest  point  of  the  ecliptic  above  the 
horizon.  Every  point,  therefore,  of  the 
ecliptic  is  the  nonagesimal  degree  in 
succession. 

NO'NAGON  (novem,  nine,  -yuvia,  an 
angle).  In  Geometry,  a  plane  figure 
having  nine  angles  and  consequently 
nine  sides.  See  Enneagon,  which  is  a 
classical  term,  the  other  being  barbarous. 

NO'NIUS.  A  former  designation  of 
the  Vernier,  from  its  having  been  sup- 
posed that  this  instrument  was  merely 
an  improvement  of  the  method  of  sub- 
division adopted  by  Nunnez,  a  Portu- 
guese.    See  Vernier. 

NO'NTRONITE.  Silicate  of  iron ;  a 
mineral  occurring  in  small  nodules  in  an 
ore  of  manganese,  and  found  in  the  de- 
partment of  Dordogne  in  France,  in  the 
arrondissement  of  Nontron. 

NOON,  REAL  and  APPARENT.  In 
Astronomy,  the  word  apparent  is  used 
not  as  opposed  to  real,  but  as  coinciding 
with  it,  and  opposed  to  mean.  Thus  ap- 
parent noon  means  real  or  true  noon, 
when  the  true  sun.  the  sun  which 
appears,  is  on  the  meridian,  as  opposed 
to  mean  noon,  when  the  mean  sun,  the 
average  fiction  of  astronomers,  which 
does  not  appear  at  all,  is  on  the  meri- 
dian.    See  Mean  Noon. 

NOOTH'S  APPARATUS.  An  appa- 
ratus invented  by  Nooth  for  making  a 
solution  of  carbonic  acid  gas. 

NORFOLK  CRAG.  A  tertiary  form- 
ation resting  on  London  clay  or  chalk. 
It  is  included  by  a  line  drawn  from 
Cromer  to  Wayburn,  and  thence  southerly 
about  eighteen  miles  towards  Norwich. 

NORMA.  The  Rule ;  a  constellation 
situated  between  Scorpio  and  Lupus. 

NORMAL   (norma,  a  rule).     From  its 

original  meaning  of  a  rule,  as  used  by 

builders,  this  term  was  used  to  signify  a 

perpendicular ;   but  it  is  generally  em- 

235 


ployed  to  denote  the  perpendicular  to  a 
curve  at  some  particular  point,  at  which 
point  the  normal  is  also  perpendicular  to 
a  tangent. 

NORMAL  GROUPS  {norma,  a  rule 
or  pattern).  Groups  of  certain  rocks 
taken  as  a  rule  or  standard. 

NORTH-WEST  CURRENT.  A 
branch  of  the  great  Equatorial  Current, 
which  separates  from  the  equatorial  at 
22°  w.  long.,  takes  a  north-western  direc- 
tion, and  is  eventually  lost  in  the  drift 
current,  to  which  it  seems  to  give  a 
north-westerly  direction,  which  is  ob- 
servable from  35°  w.  long,  to  Trinidad. 

NORTHERN  LIGHTS.  Luminous 
appearances  in  the  horizon,  less  trans- 
ient in  their  duration  than  the  light- 
ning, of  frequent  occurrence  in  the  higher 
latitudes,  more  rare  in  the  temperate 
zones,  and  scarcely  ever  seen  within  the 
tropics.  In  the  northern  hemisphere  the 
illuminated  part  surrounds  the  north 
pole,  in  the  opposite  hemisphere  the 
south  pole ;  hence  the  respective  names 
of  borealis  and  australis  applied  to  the 
aurora. 

NOTACA'NTHA  (vwrot,  the  back, 
anavOa,  a  spine).  A  section  of  Dipterous 
insects,  in  which  the  upper  part  of  the 
thorax  or  scutellum  is  armed  with  spines. 

NOTATION  {noto,  to  mark).  The 
act  or  practice  of  recording  any  thing  by 
marks,  as  by  figures  or  letters.  1.  Ma- 
thematical notation  comprises  symbols 
of  number ;  symbols  of  quantity,  which 
are  usually  letters ;  and  symbols  of  ope- 
ration, as  employed  in  algebra.  2.  Nota- 
tion in  Music  signifies  the  method 
whereby  the  pitch  or  tune,  and  the  dura- 
tion of  musical  sounds  are  represented, 
and  by  which  definite  periods  of  silence, 
called  rests,  are  marked.  It  is  to  music, 
what  letters  and  punctuation  are  to  lan- 
guage. 

NOTHOSAU'RUS  (v60os,  spurious, 
aavpa,  a  lizard).  A  spurious  kind  of 
saurian,  found  in  the  shelly  limestone 
occurring  in  the  middle  of  the  sandy  beds 
of  the  New  Red  Sandstone  Formation. 

NOTIONAL  and  RELATIONAL. 
By  these  terms,  Dr.  Becker  distinguishes 
all  the  words  of  language  into  two  classes, 
notional  words  being  those  which  ex- 
press notions,  or  objects  of  the  under- 
standing, as  verbs  and  nouns  ;  while 
relational  words  are  either  mere  termina- 
tions of  notional  words,  expressing  a 
relation  between  different  objects,  or  sepa- 
rate words  expressing  relation,  as  pre- 
positions.   The   former   class  of  words 


NUD 


NUM 


belong  to  etymology,  the  latter  to  syn- 
tax. 

NOTONECTID^l  (i/wto?,  the  back, 
veto,  to  swim).  A  family  of  the  Hydro- 
corisa,  or  water-bugs,  which  swim  on 
their  backs,  and,  from  their  peculiar 
aspect,  are  commonly  called  boat-flies 
and  water-boatmen. 

NOUN  (nomen,  a  name).  A  part  of 
speech  which  denotes  an  object,  or  the 
qualities  of  an  object.  When  it  declares 
its  own  meaning,  without  the  addition  of 
another  word,  it  is  termed  substantive; 
when  it  requires  to  be  added  {adjici)  to  a 
substantive,  which  stands  under  {sub 
stat)  and  supports  it,  and  of  which  it 
shows  the  nature  or  quality,  it  is  termed 
adjective. 

NOVA'CULITE.  Whet  slate;  a  mi- 
neral substance  found  in  beds  in  primi- 
tive and  transition  clay-slate. 

NU'CLEATED  {nucleus,  a  kernel). 
Having  a  nucleus  or  central  particle  ;  a 
term  applied  to  the  elementary  cells  of 
animal  tissues,  the  most  important  pro- 
perties of  which  reside  in  the  nucleus. 

NUCLEOBRANCHI'ATA.  The  name 
given  by  De  Blainville  to  the  fifth  order 
of  the  second  section  of  his  second  sub- 
class {Paracephalophor a  Monoica).  M. 
Rang  makes  them  the  first  order  of 
Cuvier's  class  Gasteropoda,  and  com- 
prises under  it  some  of  the  Heteropoda 
of  Lamarck,  and  the  family  Pterotrachees 
of  De  Ferussac. 

NU'CLEUS  (quasi  nuculeus,  dim.  of 
nux,  a  nut).  The  kernel  of  a  nut.  The 
solid  centre  around  which  the  particles 
of  a  crystal  are  aggregated.  The  pulpy 
conical  mass  which  constitutes  the  cen- 
tral part  of  the  ovule  in  plants.  In 
Astronomy,  the  term  nucleus  denotes 
the  apparently  solid  part  or  body  of  a 
comet,  as  seen  through  the  hazy  atmo- 
sphere which  surrounds  it. 

NUCULA'NIUM.  A  superior,  inde- 
hiscent,  fleshy  fruit,  containing  two  or 
more  cells,  and  several  seeds,  as  the 
grape.  By  Desvaux  it  was  called  bacca, 
or  berry,  from  which,  however,  it  differs 
in  being  a  superior  fruit. 

NU'CULE  {nucula,  dim.  of  nux,  a 
nut).  A  little  nut ;  a  term  applied  by 
Desvaux  to  the  fruit  of  the  oak,  the 
hazel,  &c.  It  is  more  commonly  called 
glans. 

NUDIBRANCHIA'TA  {nudus,  naked, 
branchice,  gills).  An  order  of  aquatic 
Gasteropods,  which  breathe  by  branchiae 
unprotected  by  an  external  or  internal 
6hell,  These  comprise  a  part  of  the 
236 


naked  Gasteropods  of  Cuvier.  They 
have  no  shell. 

NULLI'PORA.  A  family  of  litho- 
phytous  polyps,  the  axis  of  which  pre- 
sents no  visible  pores  on  its  surface. 
Some  naturalists  consider  that  these 
mucoso-calcareous  bodies  are  not  of  ani- 
mal origin.  Of  the  latter  opinion  is  De 
Blainville,  who  is  opposed  in  this  matter 
to  Lamarck. 

NUMBER.  The  abstract  idea  of  num- 
ber is  that  of  times  or  repetitions.  New- 
ton defines  number  as  the  abstract  ratio 
of  one  quantity  to  another  quantity  of 
the  same  species;  and  hence  there  are 
three  kinds  of  numbers — integers,  frac- 
tions, and  surds. 

1.  Number,  Abstract  and  Concrete. 
When  numbers  are  used  with  reference 
to  the  things  numbered,  they  are  said  to 
be  concrete  numbers.  When  used  with- 
out such  reference,  merely  to  indicate  a 
certain  number  of  units  of  the  same 
kind,  they  are  called  abstract  numbers. 
Thus  500  is  an  abstract,  500  pounds  a 
concrete  number.  An  abstract  number 
is  a  number  of  times ;  a  concrete,  a  num- 
ber of  things. 

2.  Number,  Perfect  and  Imperfect.  1 . 
A  perfect  number  is  that  which  is  equal 
to  the  sum  of  all  its  divisors ;  in  other 
words,  it  is  a  number  whose  aliquot 
parts,  added  together,  make  a  sum  equal 
to  the  number  itself.  Thus,  6  is  a  per- 
fect number,  for  its  divisors  or  aliquot 
parts  are  1,  2,  and  3,  and  the  sum  of 
these  is  6.  So  28  is  a  perfect  number, 
its  divisors  being  1,  2,  4,  7,  14,  the  sum 
of  which  is  28.  2.  An  imperfect  number 
is  one,  of  which  the  divisors  or  aliquot 
parts  are  not  equal  to  the  number  itself. 
Thus,  12  is  an  imperfect  number;  for  the 
sum  of  its  divisors,  1,  2,  3,  4,  6,  is  16. 

3.  Number,  Cardinal  and  Ordinal. 
Cardinal  numbers  denote  number,  as 
one,  two,  three,  &c. ;  ordinal  numbers 
denote  the  place  or  number  in  succession, 
as  first,  second,  third,  &c.  This  distinc- 
tion leads  to  a  deceptive  mode  of  speak- 
ing. "  The  real  distinction  is  that  of 
numeral  nouns  and  numeral  pronouns, 
to  the  latter  of  which  the  term  ■  ordinal ' 
might  properly  be  applied.  That  '  first, 
second,  third,'  &c,  are  properly  pro- 
nouns is  obvious,  if  we  consider  that,  so 
far  as  they  go,  this,  that,  and  the  other, 
would  supply  their  places.  The  so-called 
cardinal  numbers  denote  collections ;  the 
ordinal  numbers  point  out  only  the  places 
of  the  several  units  of  which  a  collection 
is  composed.    Even  one,  when  its  force 


NUM 


NUM 


is  simply  selective  or  distinctive,  is  a 
pronoun,  as  in  *  one  or  another ' "  (Pen. 
CycL).  If  it  be  asked,  in  what  century 
the  birth  of  a  person  occurs,  who  is  born 
in  the  year  1800,  the  answer  is, — if  born 
in  the  year  eighteen  hundred  (cardinal), 
the  birth  occurs  in  the  nineteenth  cen- 
tury ;  if  in  the  eighteen  hundredth  year 
(ordinal),  in  the  eighteenth. 

4.  Numbers,  Natural.  The  general 
name  for  the  whole  scale  of  numbers, 
1,  2,  3.  &c.  It  is  subdivided  into  the 
scale  of  odd  numbers,  1,  3,  5,  &c,  and 
even  numbers,  2,  4,  6,  &c.  These,  again, 
are  subdivided  into  oddly  odd  numbers, 
3,  7,  11,  &c. ;  evenly  odd  numbers,  1,  5, 
9,  &c. ;  oddly  even  numbers,  2,  6,  10,  &c. ; 
and  evenly  even  numbers,  4,  8,  12,  &c. 

5.  Number,  Square,  Cube,  &c.  When 
any  number  is  multiplied  by  itself  any 
number  of  times,  the  result  is  called  a 
power  of  that  number.  The  second  and 
third  powers  are  usually  called  the  square 
and  the  cube,  which  are  incorrect  names, 
derived  from  certain  connexions  of  these 
powers  with  the  square  and  the  cube  in 
geometry.  The  division  of  numbers  into 
square  numbers,  1,  4,  9,  16,  &c. ;  cube 
numbers,  1,  8.  27,  64,  &c. ;  fourth  powers, 
1,  16,  81,  256,  &c,  and  so  on,  may  be 
carried  to  any  extent. 

6.  Number,  Prime  and  Composite.  A 
prime  number  is  one  which  is  not  divi- 
sible by  any  number  except  unity  and 
itself,  as  1,  2,  3,  5,  7,  11,  13,  &c.  A  com- 
posite number  is  any  number  which  is 
not  prime. 

7.  Number,  Abundant,  Perfect,  De- 
fective. An  abundant  number  is  one,  of 
which  the  sum  of  all  its  divisors  exceeds 
itself:  thus,  12  is  an  abundant  number, 
for  1  +  2  +  3  +  4  +  6  =  16.  A  perfect  num- 
ber is  one,  or  which  the  sum  of  all  its 
divisors  is  equal  to  itself:  thus,  6  is  a 
perfect  number,  for  1+2+3  =  6.  A  de- 
fective number  is  one,  of  which  the  sum 
of  its  divisors  is  less  than  itself:  thus,  10 
is  a  defective  number,  for  1  +  2+5=8. 

8.  Numbers,  Figurate.  A  flgurate 
number  is  any  one  out  of  any  of  the  fol- 
lowing series,  the  first  excepted,  which 
is  only  introduced  as  a  basis : — 

12        3        4        5        6    &c. 

I. 

II. 

III. 

IV. 

V. 

&c. 

Each  number  is  the  sum  of  the  numbers 
in  the  preceding  row  :  thus  10  is  the  sum 
237 


1 

3 

6 

10 

15 

21 

&c. 

1 

4 

10 

20 

35 

56 

&c. 

1 

.  5 

15 

35 

70 

126 

&c. 

1 

6 

21 

56 

126 

252 

&c. 

1 

7 

28 

84 
&c. 

210 

462 

&c. 
&c. 

of  1,  3,  6  ;  70  is  the  sum  of  1,  4,  10,  20, 
35;  and  70  is  the  fifth  number  of  the 
third  order  of  figurate  numbers. 

9.  Numbers,  polygonal  and  pyramidal. 
The  principle  of  these  numbers  is  suffi- 
ciently explained  under  the  article  Figu- 
rate Numbers  (p.  136).  The  following 
are  some  of  the  polygonal  numbers  : — 
Triangular  13  6  10  15  21,  &c. 
Quadrangular  14  9  16  25  36,  &c. 
Pentagonal  1  5  12  22  35  51,  &c. 
Hexagonal        1    6     15    28    45    66,  &c. 

Pyramidal  numbers  are  formed  by 
summing  the  polygonal  numbers;  thus, 
to  find  pentagonally  pyramidal  numbers, 
take  the  pentagonal  numbers : 

1     5     12     22     35       51,    &c. 

1     6     18    40     75     125,   &c. 

10.  Numbers,  Amicable.  These  are 
numbers,  each  of  which  is  equal  to  the 
sum  of  all  the  divisors  of  the  other.  Such 
are 

284  and  220 

17,296  and  18,416 

9,363,583  and  9,437,056. 

NUMBER  of  DIRECTION.  A  num- 
ber not  exceeding  thirty-five,  which 
number  is  the  limit  of  Easter  day,  this 
day  always  falling  between  the  21st  of 
March  and  the  25th  of  April. 

NUMBERS  for  STARS.  A  mode  of 
denoting  the  stars  adopted  by  Flamsteed, 
who  numbered  them,  not  in  order  of 
brilliancy,  but  in  that  of  coming  on  the 
meridian.  Thus,  1  Orionis,  1  of  Orion, 
means  the  first  which  comes  on  the  me- 
ridian, of  all  the  stars  in  Orion  which 
Flamsteed  observed  and  recorded ;  7 
Leonis,  7  of  Leo,  is  the  star  of  this  con- 
stellation which  comes  seventh  on  the 
meridian.  So  long  as  a  star  has  either 
Bayer's  letter  (See  Letters  for  Stars)  or 
Flamsteed's  number,  both  are  used  indif- 
ferently and  perfectly  understood ;  nor  is 
it  expected  that  there  will  be  any  con- 
nexion between  the  letter,  which  refers, 
or  was  supposed  to  refer,  to  the  bright- 
ness of  the  star,  and  the  number,  which 
is  derived  from  its  position.  Thus  1  Vir- 
ginis  happens  to  have  w  for  its  letter;  it 
is  only  of  the  sixth  magnitude,  though  it 
comes  early  to  the  meridian;  but  a  Vir- 
ginis,  a  splendid  star,  is  67  Virginis  in 
Flamsteed. 

NUMERATION  (numerus,  a  number\ 
A  method  of  calculating  numbers  by 
means  of  ten  sipns,  viz  a  cipher  and 
nine  digits.  Higher  numbers  are  sig- 
nified by  placing  these  signs  by  the  side 
of  one  another,  and  agreeing  that  the 
first  figure  on  the  right  hand  shall  retain 


0  BL 


OB  L 


the  value  which  it  has  when  it  stands 
alone ;  that  the  second  on  the  right  hand 
shall  mean  ten  times  as  many  as  it  does 
when  it  stands  alone;  that  the  third 
shall  mean  one  hundred  times  as  many 
as  when  it  stands  alone;  the  fourth,  one 
thousand  times ;  and  so  on. 

NUMERATOR.  In  arithmetic,  that 
part  of  a  fraction  which  denotes  how 
many  of  the  aliquot  parts  of  an  integer 
or  unit  are  taken,  the  nature  of  these 
parts  being  expressed  by  the  denomi- 
nator. Thus  |  denotes  five,  not  of  units, 
but  of  sixths  of  a  unit;  six  is  the  deno- 
minator, 5  the  numerator  or  numberer 
of  the  parts  taken. 

NUMERICAL.  In  Algebra,  this  term 
is  applied  to  co-efficients  which  consist  of 
numbers,  as  distinguished  from  literal 
co-efficients,  which  consist  of  letters.  As 
opposed  to  algebraical,  it  is  applied  to  the 
magnitude  of  a  quantity,  considered  irre- 
spectively of  its  symbol;  thus  — 20  is 
numerically  greater  than  — 10,  though 
algebraically  less. 

NU'MMULITES  {nummus,  money,  \l- 
$ov,  a  stone).  An  extinct  genus  of  the 
order  of  molluscous  animals,  called  Ce- 
phalopods,  of  a  thin  lenticular  shape, 
resembling  a  coin,  internally  divided  into 
small  chambers. 

NUT.  A  dry,  bony,  indehiscent,  one- 
celled  fruit,  proceeding  from  a  pistil  of 
three  cells,  and  enclosed  in  a  cupule,  as 


in  the  hazel,  the  acorn,  &c.  The  term 
is  sometimes  applied  to  the  fruit  of 
borago,  lithospermum,  &c,  but  these 
fruits  are  more  properly  called  akenia. 
The  term  nux  baccata  is  sometimes  ap- 
plied to  the  fruit  of  taxus,  &c. 

NUTA'TION  (nuto,  to  nod).  The 
term  applied  to  a  small  and  slow  gyratory 
movement  of  the  earth's  axis,  by  which, 
if  subsisting  alone,  the  pole  would  de- 
scribe among  the  stars,  in  a  period  of 
nineteen  years,  a  minute  ellipse,  having 
its  longer  axis  equal  to  18"  5,  and  its 
shorter  to  13"*74;  the  longer  being  di- 
rected towards  the  pole  of  the  ecliptic, 
the  shorter  at  right  angles  to  it. 

NU'TTALITE.  A  mineral  associated 
with  calc-spar,  from  Bolton  in  Massa- 
chusetts. It  appears  to  be  an  alumino- 
silicate  of  lime,  potash,  and  iron. 

NYCTERIBI'ID^S.  The  Bat-lice;  a 
family  of  dipterous  pupiparous  insects, 
parasitic  on  bats,  and  approaching  to 
the  spiders  in  form. 

NYMPH.  A  fanciful  term  for  the 
chrysalis  or  pupa  state  of  insect  life,  ap- 
plied to  the  active  pupae  of  orthopterous 
and  hemipterous  insects. 

NYSSO'NIDjE.  A  family  of  hymeno- 
pterous  insects  belonging  to  the  section 
Fossores,  named  from  the  genus  Nysson, 
and  characterized  principally  by  the 
absence  of  a  notch  on  the  inner  side  of 
the  mandibles. 


O 


OB-.  A  Latin  preposition,  in  compo- 
sition signifying  inversion :  thus  oft-ovate 
means  inversely  ovate ;  oft-conical,  in- 
versely conical.  It  is  obvious  that  this 
term  can  only  be  employed  in  words 
which  denote  that  one  end  of  a  body  is 
wider  than  the  other.  Hence,  it  is  super- 
fluous in  such  a  word  as  oft-lanceolate. 

OBJECTIONS,  FALLACY  OF.  A 
fallacious  mode  of  argument,  by  which 
it  is  shown  that  there  are  objections 
against  some  plan,  theory,  or  system, 
and  thence  it  is  inferred  that  it  should 
be  rejected ;  whereas  that  which  ought 
to  have  been  proved  is,  that  there  are 
more  or  stronger  objections  against  the 
receiving  than  the  rejecting  of  it. 

OBLATE.  A  term  signifying  the  re- 
verse of  oblong,  or  shorter  in  one  direc- 
tion than  in  another,  and  applied  to  a 
238 


spheroid  which  is  made  by  the  revolution 
of  an  ellipse  about  the  smaller  of  the 
two  axes.  Thus  the  earth  is  an  oblate 
spheroid,  the  actual  difference  between 
the  polar  and  the  equatorial  diameters 
being  in  the  proportion  of  300  to  301. 

OBLIQUE.  A  term  generally  em- 
ployed in  opposition  to  direct  or  right. 
In  astronomical  language,  the  term  ob- 
liquity denotes  the  angle  made  by  the 
ecliptic  with  the  equator.  The  greatest 
latitude  at  which  the  sun  ever  appears 
vertical  is  the  obliquity  of  the  ecliptic 
(See  Ascension).  In  stereographic  pro- 
jection, an  oblique  circle  is  any  circle 
oblique  to  the  line  of  projection.  Oblique 
planes,  in  dialling,  are  planes  which  re- 
cline from  the  zenith.  Oblique  projection, 
in  mechanics,  is  the  projection  of  a  body 
at  an  oblique  angle  with  the  horizontal 


OCE 

line.  Oblique  sailing,  in  navigation,  is 
that  which  includes  the  calculation  of 
oblique-angled  triangles.  Oblique  sphere, 
in  geography,  is  that  in  which  the  axis  of 
the  earth  is  inclined  to  the  horizon  of 
the  place. 

OBLONG  (oblongus,  of  a  figure  inclin- 
ing to  long).  A  four-sided  figure,  which, 
like  the  square,  has  all  its  angles  right 
angles,  hut,  unlike  the  square,  has  not  all 
its  sides  equal.  The  term  rectangleis  often 
used  for  it,  but  is  obviously  objectionable. 
An  oblong  spheroid,  also  called  the  pro- 
late spheroid,  is  generated  by  the  revo- 
lution of  an  ellipse  about  its  longer  axis, 
and  is  therefore  elongated  at  the  poles. 

OBSI'DIAN.  A  volcanic  product,  or 
species  of  lava,  very  like  common  green 
bottle-glass,  which  is  almost  black  in 
large  masses,  but  semi-transparent  in 
thin  masses.  Pumice-stone  is  obsidian 
in  a  frothy  state,  produced,  most  pro- 
bably, by  water  which  had  been  contained 
in,  or  had  access  to,  the  melted  stone, 
and  converted  into  steam.  Solid  obsi- 
dian often  occurs  in  masses,  which  are 
partially  converted  into  pumice.  The 
name  is  derived  from  that  of  Obsidius, 
who  first  found  it  in  Ethiopia. 

OBSOLETE  {obsoletus,  gTOwn  out 
of  use).  A  term  denoting  a  faint  indi- 
cation of  a  character.  Thus,  the  calyx 
of  Conium  is  represented  by  an  obsolete 
margin  ;  slight  and  indistinct  striae  upon 
a  shell  are  termed  obsolete  striae.  In 
these  cases,  however,  the  obsolete  state 
is  not  the  result  of  accident,  but  of  par- 
tial development. 

OBTUSE.  Blunt  or  dull ;  opposed  to 
acute,  as  applied  to  an  angle  which  is 
greater  than  one  right  angle  and  less  than 
two ;  in  other  words,  an  angle  which 
measures  more  than  90  and  less  than 
180  degrees. 

O'BVOLUTE  (obvolutus,  rolled  over). 
A  form  of  aestivation  or  vernation,  in 
which  the  margins  of  one  leaf  alternately 
overlap  those  of  the  leaf  which  is  oppo- 
site to  it. 

OCCULT  SCIENCES.  Hidden  sci- 
ences; imaginary  sciences,  as  alchemy, 
astrology,  magic,  &c. 

OCCULTA'TION  (occulto,  to  hide). 
In  astronomy,  the  eclipsing  of  a  fixed 
star  by  the  interposition  of  the  moon. 

OCEAN.  The  one  continuous  fluid 
which  spreads  over  nearly  seven-tenths 
of  the  globe,  all  the  gulfs  and  inland  seas 
being  branches  of  this  universal  ocean. 
Different  names  have,  however,  been 
given  to  various  parts  of  it : — 
239 


OCT 

I.  South-Eastern  Basin. 

1.  Antarctic  Ocean.  Comprised  within 
the  Antarctic  circle  ;  that  is,  between  the 
parallel  of  66°  32'  of  southern  latitude 
and  the  South  Pole. 

2.  Southern  Ocean.  Bounded  on  the 
one  side  by  the  Antarctic  circle,  and  on 
the  other  by  a  line  drawn  from  Cape 
Horn  to  the  Cape  of  Good  Hope,  thence 
to  Van  Dietnen's  Land,  and  again  by  the 
south  of  New  Zealand  to  Cape  Horn. 

3.  Indian  Ocean.  Lying  between  Africa 
on  the  west,  and  the  peninsula  of  Malaya 
with  the  islands  of  Sumatra,  Java,  &c, 
and  New  Holland,  on  the  east,  and 
bounded  by  Persia  and  Hindostan  on  the 
north.  The  Red  Sea  or  Arabian  Gulf, 
the  Persian  Gulf,  and  the  Bay  of  Bengal, 
are  all  parts  of  this  ocean. 

4.  Pacific  Ocean.  Divided  by  the  equa- 
tor into  North  and  South,  and  inclosed 
between  America  on  the  east,  and  New 
Holland,  the  islands  of  Java  and  Su- 
matra, and  the  continent  of  Asia,  on  the 
west.  On  the  north  it  terminates  at 
Behring's  Straits.  The  seas  of  China, 
Japan,  Okhotsk,  &c,  form  parts  of  this 
ocean. 

II.  Western  Basin. 

1.  Atlantic  Ocean.  Commencing  in 
the  south  from  a  line  drawn  from  Cape 
Horn  to  the  Cape  of  Good  Hope,  and  ter- 
minated on  the  north  by  the  Arctic  circle. 
It  is  divi  led  into  the  North  and  South  by 
the  equator,  and  its  branches  are  the 
Mediterranean,  the  North  Sea  or  German 
Ocean,  the  Baltic,  Baffin's  Bay,  Hudson's 
Bay,  the  Gulf  of  Mexico,  and  the  Carib- 
bean Sea. 

2.  Arctic  Ocean.  Surrounding  the 
North  Pole,  and  bounded  by  the  Arctic 
circle  and  the  northern  shores  of  the  two 
continents.  The  White  Sea,  the  Sea  of 
Kara,  and  the  Gulf  of  Obe,  are  parts  of 
it. 

O'CHRE.  Hydrated  sesquioxide  of 
iron ;  an  argillaceous  earth,  impregnated 
with  iron  of  a  red  or  yellow  colour. 

O'CHREA.  Literally,  a  boot;  and 
hence  applied,  in  botany,  to  the  mem- 
branous tube  which  sheaths  the  stem  of 
rhubarb  and  other  plants,  and  consists  of 
two  stipules,  cohering  by  their  margins. 

O'CTAGON  Coktu>,  eight,  ^tovia,  an 
angle).  A  plane  geometrical  figure,  con- 
tained by  eight  sides,  and  consequently 
having  eight  angles.  When  the  sides 
and  angles  are  equal,  the  figure  is  a 
regular  octairon. 

OCTAHE'DRITE  (okto>,  eight,  edpa, 
a  seat).    Anatase.     Pyramidal  titanium 


CEST 


OLE 


ore,  from  Bourg  d'Oisans,  whence  it  is 
also  called  Oisanite. 

OCTAHE'DRON  (k™,  eight,  e&pa, 
a  seat).  In  Geometry,  a  solid  figure  con- 
tained by  eight  equal  and  equilateral 
triangles. 

OCTANDRIA  (i*™,  eight,  ixvtjp,  a 
male).  The  eighth  class  of  plants  in  the 
Linnaean  system,  characterized  by  their 
flowers  having  eight  stamens. 

Octo-gynia  (yvvt],  a  female).  The  name 
given  by  Linnaeus  to  those  orders  of 
plants  which  have  eight  pistils  in  their 
flowers. 

O'CTANS  HADLEIE'NSIS.  Hadley's 
Octant ;  a  modern  southern  constellation, 
consisting  of  forty-three  stars. 

OCTANT.  A  term  applied  to  an  in 
termediate  point  between  a  quadrature 
and  a  syzygy  of  the  moon.  See 
Phases. 

O'CTAVE  (octavus,  the  eighth).  In 
Music,  the  simplest  and  most  consonant 
interval,  in  which  the  higher  note  makes 
twice  as  many  vibrations  as  the  funda- 
mental note  from  which  it  is  derived  ;  its 
ratio  is,  therefore,  that  of  1  J  2  *  *  4  *  8, 
&c.  This  relation  serves  as  the  principal 
unit  of  measurement  in  music,  its  entire 
range  embracing  at  most  nine  entire 
octaves,  rising  from  the  deepest  note, 
which  makes  32  vibrations  in  a  second, 
to  the  highest,  which  performs  16,384 
vibrations  in  the  same  time. 

OCTO'PODA(oktw,  eight,  novs,  7ro36r, 
a  foot).  A  designation  of  animals  which 
have  eight  feet.  The  name  of  those 
Cephalopods  which  have  eight  prehensile 
organs  attached  to  the  head. 

OCYPO'DIANS  (wkm,  swift,  ttow,  a 
foot).  A  tribe  of  brachyurous  crustace- 
ans, placed  by  Milne  Edwards  between 
the  Pinnotherians  and  the  Gonoplacians, 
and  named  from  the  genus  Ocypoda.  The 
family  are  characterized  by  their  rapidity 
in  running. 

O'DERIT.  An  opaque  black  sub- 
stance, occurring  in  Sweden :  it  is  pro- 
bably black  mica ;  for  it  is  capable  of  being 
split,  like  mica,  into  thin  leaves. 

CSNANTHIC  ETHER  (cuW,  wine, 
avOos,  flower).  An  oily  liquid,  which 
gives  the  characteristic  odour  to  all 
wines. 

(Enanthic  acid.  An  acid  found  in  the 
foregoing  compound,  in  combination  with 
ether. 

CE'STRIDiE  {oestrus,  a  gad-fly).  The 
Bot-flies ;  a  family  of  Dipterous  insects, 
belonging  to  the  section  Athericera,  re- 
markable for  the  peculiar  habitation  of 
210 


the  larvae,  and  for  the  absence  of  any 
proper  mouth  in  the  imago  state. 

OFFICI'NA  SCULPTORIA.  A  mo- 
dern southern  constellation,  consisting  of 
twelve  stars. 

OFFING.  If  we  sail  out  of  sight  of 
land,  whether  we  stand  on  the  deck  of 
the  ship,  or  climb  the  mast,  we  see  the 
surface  of  the  sea — not  losing  itself  in 
distance  and  mist,  but  terminated  by  a 
sharp,  clear,  well-defined  line,  or  offing, 
as  it  is  called,  which  runs  all  round  us  in 
a  circle,  having  our  station  for  its  centre. 

O'FFSET.  Propagulum.  A  short 
branch  of  certain  herbaceous  plants, 
which  is  terminated  by  a  tuft  of  leaves, 
and  is  capable  of  taking  root  when  sepa- 
rated from  the  parent  plant,  as  in  house- 
leek.     It  differs  little  from  the  runner. 

O'GAM  or  OGMA.  An  occult  form 
of  writing  among  the  Irish,  apparently 
of  great  antiquity.  The  term  is  a  primi- 
tive Celtic  word,  signifying  the  secrets  of 
letters. 

OGYGIAN  DELUGE.  A  great  in- 
undation mentioned  in  fabulous  history, 
as  having  taken  place  in  the  time  of 
Ogyges,  king  of  Attica,  whose  death  is 
fixed  in  Blair's  chronological  tables  in 
the  year  b.c.  1764. 

OHM'S  LAW.  An  important  law 
which  refers  to  all  the  causes  which  tend 
to  impede  the  action  of  the  voltaic  bat- 
tery. It  is,  that  "  the  intensity  of  an  elec- 
tric current,  when  a  battery  is  in  action, 
is  directly  as  the  whole  electromotive 
force  in  operation,  and  inversely  as  the 
sum  of  all  the  impediments  to  conduc- 
tion." It  may,  therefore,  be  expressed  by 
a  fraction,  whose  numerator  is  the  elec- 
tromotive force,  and  its  denominator  the 
sum  of  the  resistance  of  all  its  parts. 

OI'SANITE.  An  ore  of  titanium,  from 
the  department  of  Oise. 

OLD  RED  SANDSTONE.  A  forma- 
tion lying  immediately  below  the  Car- 
boniferous group.  The  term  Devonian 
has  been  recently  proposed  for  strata  of 
this  age,  because  in  Devonshire  they  are 
largely  developed,  and  contain  many 
organic  remains. 

OLEA'CEjE.  The  Olive  tribe  of  dico- 
tyledonous plants.  Trees  or  shrubs 
with  leaves  opposite ;  flowers  regular, 
monopetalous,  hermaphrodite,  or  dioe- 
cious ;  stamens  two ;  ovarium  simple, 
superior,  2-celled ;  seeds  pendulous. 

OLEFIANT  GAS  {oleum,  oil,  fio,  to 
become).  A  compound  gas  consisting 
of  carbon  vapour  and  hydrogen,  and  now 
viewed  as  a  compound  of  the  organic 


ON  U 


OPA 


radical  acetyl  with  hydrogen.  Its  name 
was  derived  from  its  forming  an  oily 
substance  with  chlorine. 

OLEIC  ACID  {oleum,  oil).  An  acid 
forming  the  essential  part  of  fat  oils 
which  are  not  drying,  as  oil  of  almonds. 

OLEO-RESINS.  Native  compounds 
of  volatile  oil  and  resin,  the  proper  juices 
of  coniferous  and  other  plants. 

O'LIGIST  IRON.  A  subspecies  of 
rhomboidal  iron  ore,  comprising  the  com- 
mon specular,  and  the  micaceous  spe- 
cular varieties. 

OLIGO-  (6\t7os,  little,  few).  A  term 
used  in  Greek  compounds,  to  denote  that 
the  number  of  any  thing  is  small,  not 
indefinite.  It  is  contrasted  by  the  pre- 
fix poly-  (iroXvs,  many),  signifying  that 
the  number  is  large  and  not  definite. 
Thus  we  have  o/i^o-spermous  and  poly- 
spermous  fruits. 

OLIVE  MALACHITE.  Octahedral 
phosphate  of  copper,  from  Lebethen  in 
Hungary. 

OLIVE  ORE.  Olivenite.  One  of  the 
arseniates  of  copper. 

OLIVILE  (olea,  the  olive).  The 
name  given  by  Pelletier  to  a  peculiar 
substance  which  remains  after  gently 
evaporating  the  alcoholic  solution  of 
the  gum  which  exudes  from  the  olive 
tree. 

OLI'VIN^.  An  aberrant  sub-family 
of  the  VolutidcB,  or  volutes,  named  from 
the  typical  genus  oliva ;  these  shells  are 
cylindrical  in  shape ;  the  aperture  is 
linear,  and  the  pillar  thickened  and  con- 
fusedly plaited. 

O'LIVINE  {olea,  the  olive).  An  olive- 
coloured  silicate  of  lime  and  magnesia. 
In  its  purer  state  it  is  denominated 
chrysolite  or  peridot ;  and  when  protox- 
ide of  iron  is  predominant,  it  has  by 
some  been  called  hyalosiderite. 

OMNI'VOROUS  {omnis,  all,  voro,  to 
devour).  A  term  applied  to  animals 
which  feed  on  all  substances  indifferently. 
The  term  is  synonymous  with  the  Greek 
pantophagous. 

O'MPHACITE.  A  variety  of  augite, 
of  a  pale  green  colour,  occurring  in  primi- 
tive rocks,  with  precious  garnet,  in  Ca- 
rinthia. 

OMPHALO'DIUM  (oMtf>a\69,  the  um- 
bilicus). A  term  applied  by  Turpin  to 
the  centre  of  the  hilum  of  the  seeds  of 
plants,  through  which  the  nutrient  ves- 
sels pass  to  the  embryo. 

ONUS  PROBANDI.  The  burden  of 
proof,  in  Rhetoric,  rests  with  him  who 
would  deny  any  generally  received 
241 


opinion,  as  that  of  gravitation,  that  of 
the  Copernican  theory,  &c. 

O'NYX  (ovi/?,  onyx,  a  nail).  A  variety 
of  agate,  in  which  the  siliceous  particles 
are  disposed  in  alternating  horizontal 
layers  of  opaque  white,  and  translucent 
blue,  grey,  or  brown,  resembling  the 
marks  on  the  human  nail. 

O'OLITE  {d)6v,  an  egg,  XiOos,  a  stone). 
A  limestone ;  so  named  from  its  being 
composed  of  rounded  particles,  like  the 
roe  or  eggs  of  a  fish.  The  term  is  also 
applied  to  a  large  group  of  strata,  charac- 
terized by  peculiar  fossils,  in  which 
limestone  of  this  texture  occurs. 

1.  Lower  Oolite.  A  series  of  strata  of 
oolitic  limestone,  clays,  and  marls,  re- 
posing above  the  lias,  and  divisible  into 
the  Lower  or  Cheltenham  Oolite,  Fuller's 
Earth,  Stonesfield  Siate,  Great  Oolite, 
Forest  Marble,  and  Corn-brash. 

2.  Middle  Oolite.  A  series  of  strata, 
consisting  of  coralline  and  shelly  oolitic 
limestone,  calcareous  sandstone,  and 
clays,  separated  from  the  Lower  Oolite 
by  a  great  deposit  of  clay,  and  divisible 
into  Oxford  Clay,  Calcareous  Grit  or 
Sandstone,  Coral  Rag  and  Oolite,  and 
Calcareous  Sandstone. 

3.  Upper  Oolite.  A  series  of  strata 
separated  from  the  Middle  Oolite  by  a 
great  deposit  of  clay,  and  divisible  into 
the  Kimmeridge  Clay,  Portland  Sand, 
and  Portland  Oolite. 

OOZO'A  (tioi/,  an  egg,  £5>ov,  an  ani- 
mal). A  designation  given  by  Carus  to 
one  of  the  primary  divisions  of  the  Ani- 
mal Kingdom,  from  the  resemblance  of 
the  beings  composing  it  to  the  eggs  or 
rudiments  of  more  perfect  forms.  They 
correspond  wih  the  Acrita  of  Macleay, 
the  Cryptoneura  of  Rudolphi,  and  the 
Protozoa  of  other  writers. 

OPA'CITY  {opticus,  dark).  A  quality 
of  bodies  which  renders  them  impervious 
to  the  rays  of  light.  In  this  respect 
opaque  bodies  are  the  reverse  of  the 
transparent;  but  their  opacity  is  occa- 
sioned rather  by  their  thickness  than 
their  absolute  impermeabiliiy  to  light. 
Gold  is  considered  opaque ;  but  the  rays 
of  a  candle,  or  of  the  sun,  falling  on  a 
sheet  of  gold  leaf  laid  on  glass,  are  trans- 
mitted as  a  faint  green  glimmering  light. 

OPAL.  Opaline  substances  are  mostly 
hydrates  of  silica,  and  are  named — 

1.  Precious  or  Noble  Opal,  which  owes 
its  beautiful  play  of  colours  to  a  multi- 
plicity of  imperceptible  fissures  in  its 
interior.  A  variety  of  this  kind  has  the 
property  of  becoming  transparent  when 
M 


O  PP 


ORC 


immersed  in  water,  and  is  called  hydro- 
phane,  oculus  mundi,  or  changeable 
opal. 

2.  Sun  or  Fire  Opal,  of  a  hyacinth-red 
colour,  changing  to  a  paler  hue  by  heat ; 
found  only  at  Zimapan  in  Mexico,  in  a 
particular  variety  of  hornstone  porphyry. 

3.  Common  Opal,  a  translucent  white 
variety  of  which,  appearing  yellow  or  red 
when  held  between  the  eye  and  the  light, 
is  called  girasol. 

4.  Semi-opal,  agreeing  in  its  principal 
characters  with  common  opal,  and  pre- 
senting spotted,  striped,  or  brown  de- 
lineations. 

5.  Mother-of-pearl  Opal,  or  Cacholong, 
described  as  a  variety  of  quartz,  found  in 
the  river  Cach  in  Bucharia. 

6.  Jasper  Opal,  or  ferruginous  opal,  of 
a  scarlet-red  and  grey  colour,  referred  by 
some  authors  to  jasper. 

7.  Wood  Opal,  or  opalized  wood,  con- 
sisting of  wood  petrified  by  silicious 
earth,  and  acquiring  a  structure  similar 
to  simple  mineral  opal. 

8.  Liver  Opal,  or  menilite,  found  at 
Menil-Montant,  near  Paris,  in  a  bed  of 
adhesive  slate. 

OPE'RCULUM  {operio,  to  shut  up). 
A  cover  or  lid.  In  Malacology,  the  term 
operculum  denotes  the  hard  lid,  either 
corneous  or  calcareous,  which  closes  the 
mouth  of  many  spiral  shells,  and  is  car- 
ried on  the  posterior  part  of  the  belly  of 
the  animal. 

OPHI'DIA  {o(pn,  a  serpent).  An  order 
of  Reptiles,  comprising  the  Serpents, 
which  have  no  atlantal  or  sacral  extre- 
mities perceptible  externally,  and  conse- 
quently no  members  or  appendages  of 
locomotion. 

OPPOSITE  TERMS.  In  logic,  those 
terms  are  said  to  be  opposite,  or  incon- 
sistent, which  express  qualities  inap- 
plicable to  the  same  object  at  the  same 
time,  as  "  black  and  white."  Relative 
terms  are  opposite,  only  when  applied 
with  reference  to  the  same  subject :  as 
one  may  be  both  Master  and  Servant ; 
but  not  at  the  same  time  to  the  same 
person. 

OPPOSITION.  Two  bodies  are  in 
conjunction,  when  they  are  at  the  same 
point  of  a  circle  ;  and  in  opposition,  when 
they  are  at  opposite  points.  For  the  ap- 
plication of  these  terms  in  Astronomy, 
see  Conjunction  and  Opposition. 

OPPOSITION,  LOGICAL.  Two  pro- 
positions are  said  to  be  opposed  to  each 
other,  when,  having  the  same  subject 
and  predicate,  they  differ,  in  quantity,  or 
242 


quality,  or  both.  The  four  kinds  of  op- 
position are  termed  contraries,  sub- 
contraries,  subalterns,  and  contradic- 
tories. 

O'PTICS  (Stttoaicu,  to  see).  That 
branch  of  natural  science  which  treats  of 
the  properties  of  light  and  vision  ;  in  its 
proper  acceptation,  it  relates  to  direct 
vision,  while  catoptrics  treats  of  reflected, 
and  dioptrics  of  refracted  vision.  Prac- 
tical Optics  is  the  application  of  the  phy- 
sical properties  of  light,  and  the  mathe- 
matical laws  of  optics  to  the  construction 
of  optical  instruments. 

O'RBIT  {orbita,  a  track).  The  course 
which  a  star  describes  around  the  sun  or 
another  star.  The  Latin  word  orbis  is  a 
circle,  or  a  globe ;  and  hence  the  paths 
of  the  planets  round  the  sun  are  termed 
orbits,  and  the  planets  themselves  orbs, 
although  the  former  are  now  understood 
to  be  elliptical,  and  the  latter  spheroidal. 
The  earth's  orbit  is  the  ecliptic. 

1.  Orbit,  Plane  of.  The  plane  of  an 
orbit  is  an  imaginary  surface,  passing 
from  one  extremity,  or  side  of  the  orbit 
to  the  other.  If  the  rim  of  a  drum-head 
be  considered  the  orbit,  its  plane  would 
be  the  parchment  extended  across  it,  on 
which  the  drum  is  beaten. 

2.  Orbits,  inclination  of.  If  we  sup- 
pose planes  to  pass  through  the  orbits  of 
the  planets,  and  to  be  indefinitely  ex- 
tended, all  these  planes  will  pass  through 
the  sun's  centre;  but  all  of  them  will 
cut  the  plane  of  the  ecliptic,  though  at 
different  angles,  which  are  respectively 
called  the  inclination  of  the  orbits.  The 
average  inclination  of  the  moon's  orbit 
is  about  five  degrees. 

ORBITE'LJE  (orbis,  an  orb,  tela,  a 
web).  A  family  of  Spiders,  which  spread 
abroad  webs  of  a  regular  and  open  tex- 
ture, either  circular  or  spiral,  and  remain 
in  the  middle,  or  on  one  side,  in  readiness 
to  spring  upon  an  entangled  insect. 

ORCEIN.  A  red  colouring  matter 
found  in  archil,  and  referred  by  Dr.  Kane 
to  a  mixture  of  two  substances,  which 
he  terms  alpha-orcein  and  beta-orcein, 
the  latter  being  produced  by  oxidation  of 
the  former. 

ORCHIDA'CEiE.  The  Orchis  tribe 
of  Monocotyledonous  plants,  in  which 
the  stamens  and  the  style  are  consoli- 
dated into  a  central  column,  and  the 
ovary  is  inferior.  They  correspond  with 
the  Gynandria  Monandria  of  Linnaeus. 

ORCIN.  A  colourless  matter  procured 
from  the  lichen  dealbatus,  assuming  a 
deep  violet  colour  when  exposed  to  am- 


ORI 


ORT 


monia  and  air,  owing  to  the  formation  of 
orcein. 

O'RDINATE  {ordino,  to  arrange).  A 
term  applied,  in  Conic  Sections,  to  one 
half  of  any  line  drawn  across  an  ellipse, 
parallel  to  the  minor  axis.  The  whole 
line  is  called  a  double  ordinate,  and  the 
portion  of  the  major  axis  which  it  cuts 
off  is  called  an  abscissa.  These  terms 
are  equally  and  similarly  applicable  to 
the  parabola  and  the  hyperbola. 

ORES.  The  mineral  bodies  from 
which  metals  are  extracted.  These  are 
termed  sulphurets,  when  combined  with 
sulphur;  oxides,  when  combined  with  oxy- 
gen ;  and  salts,  when  combined  with  acids. 

ORGA'NIC  REMAINS  (Spyavov,  an 
organ).  The  remains  of  organized  bodies, 
both  plants  and  animals,  found  in  a  fossil 
state. 

ORGANO'GRAPHY  (opyavov,  an 
organ,  ypdcpta,  to  describe).  By  this  term 
De  Candolle  designated  his  learned 
work  on  the  structure  of  plants;  and 
although  the  word  simply  means  a  "de- 
scription of  organs,"  it  has  been  restricted 
to  the  organs  of  plants,  comprising  an 
account  of  their  elementary  tissues,  and 
of  their  compound  structures. 

O'RGANON  {opyavov,  an  instrument 
or  machine).  A  philosophical  term,  de- 
noting a  method,  and  usually  applied  to 
a  body  of  rules  and  laws  for  conducting 
a  scientific  inquiry.  What  is  called  the 
Organon  of  Aristotle,  is  a  collection  of 
the  views  of  that  philosopher  on  the 
several  subjects  of  the  Categories,  includ- 
ing his  Logic ;  of  the  Interpretation  or 
the  Nature  of  Propositions  ;  of  the 
former  and  latter  Analytics ;  of  Topics  ; 
and  of  Sophisms.  The  term  organon 
was  not  given  by  Aristotle,  but  is  of  a 
date  posterior  to  him. 

Novum  Organon  Scientiarum.  The 
name  given  by  Bacon  to  his  learned  work 
on  "  A  New  Method  of  studying  the 
Sciences."  This  method,  which  is  founded 
on  the  principle  of  Induction,  or  actual 
experiment,  which  Bacon  significantly 
terms  "Asking  Questions  of  Nature," 
has  earned  for  its  author  the  appellations 
of  the  Prophet  of  the  Arts  and  the  Father 
of  Experimental  Philosophy.  See  Baco- 
nian Philosophy. 

ORIOLI'NiE  {oriolus,  the  oriole). 
Orioline  birds,  or  Orioles ;  a  family  of 
the  Cantatrices  of  Macgillivray,  belonging 
to  the  warmer  regions  of  the  Old  Con- 
tinent. They  appear  to  be  allied  to  the 
Rollers,  not  only  in  the  form  of  the  bill, 
but  also  in  their  short  tarsi  and  broad  toes. 
243 


ORI'ON.  A  southern  constellation, 
consisting  of  seventy-eight  stars,  the 
principal  of  which  is  Betelgeuse. 

ORNITHO'LOGY  (6'pw?,  a  bird,  \6- 
709,  an  account).  The  science  which 
teaches  the  natural  history  and  arrange- 
ment of  birds.     See  Zoology. 

O'RPIMENT  (auri  pigmentum).  A  ge- 
neral name  for  two  sulphurets  of  arsenic, 
the  yellow,  or  prismatoidal  sulphur,  and 
the  red,  ruby  sulphur,  or  hemi-prismatic 
sulphur.  The  former  is  the  colouring 
principle  of  the  paint  called  King's  yellow. 

O'RRERY.  A  machine  for  repre- 
senting the  motions,  relative  magnitudes, 
and  distances  of  the  bodies  composing 
the  solar  system ;  said  to  have  been 
named  after  an  earl  of  Orrery,  for  whom 
the  first  machine  of  the  kind  was  made 
by  Prince  Eugene.  Planetary  machines 
have  received  various  names,  sufficiently 
indicative  of  their  object,  viz.,  planeta- 
rium, tellurian,  lunarian,  and  satellite 
machine. 

ORSEDEW.  Manheim  or  Dutch  Gold ; 
an  inferior  sort  of  gold  leaf,  prepared  of 
copper  and  zinc,  sometimes  called  leaf 
brass,  and  principally  manufactured  at 
Manheim. 

O'RTHITE  {bp66t,  upright).  A  sili- 
cate containing  yttria  and  protoxide  of 
cerium,  and  named  from  its  always  oc- 
curring in  straight  layers,  generally  in 
felspar. 

ORTHOCERA'TA  {bP06s,  straight, 
Kepac,  a  horn).  An  extinct  genus  of 
Cephalopods,  which  inhabited  a  long- 
chambered  conical  shell,  like  a  straight 
horn. 

ORTHOGO'NAL  (oP0or,  right,  ywia, 
an  angle).  In  Geometry,  this  term  simply 
means  at  right  angles,  or  perpendicular  • 
thus,  a  curve  cuts  a  set  of  curves  ortho- 
gonally, when  it  cuts  them  all  at  right 
angles.  The  term  is  sometimes  used 
synonymously  with  orthographic,  and 
relates  to  a  particular  mode  of  projection. 
See  Projection. 

ORTHO'GRAPHY  (bP06?,  right,  ypd- 
<pas,  to  write).  In  its  general  sense,  this 
term  denotes  that  part  of  Grammar  which 
teaches  the  nature  and  powers  of  letters, 
and  the  correct  method  of  spelling  and 
writing  words.  The  sense  of  the  word 
has,  however,  been  restricted  by  gram- 
marians to  the  proper  selection  of  the 
letters  of  words,  and  the  correct  division 
of  words  when  separated  by  the  termina- 
tion of  lines. 

ORTHO'PTERA  (bpOos,  straight,  me- 
pbv,  a  wing).  An  order  of  insects,  com- 
M2 


OST 


OVA 


prising  the  locusts,  grasshoppers,  crickets, 
&c. ;  having  their  anterior  wings  coria- 
ceous and  overlapping  each  other;  the 
posterior  partly  coriaceous,  partly  mem- 
branous, and  folded  longitudinally  when 
at  rest. 

O'RTIVE  AMPLITUDE  (ortus,  a 
rising).  An  astronomical  term,  denoting 
the  arc  of  the  horizon  intercepted  be- 
tween the  point  where  a  star  rises  and 
the  east  point.  Hence  it  is  also  called 
eastern  amplitude. 

ORY'CTOGNO'SY  (oPi/kto?,  dug  up, 
•yvwaiv,  knowledge).  Oryctology.  That 
branch  of  science  which  relates  to  fossil 
organic  remains.  The  term  is  sometimes 
applied  to  that  branch  of  mineralogy 
which  relates  to  the  classification  of 
minerals. 

OSCILLATION  (oscillum,  an  image 
hung  on  ropes,  and  swung  up  and 
down  in  the  air).  The  swinging  or  vi- 
bratory motion  by  which  a  body,  when 
made  to  change  its  place,  returns  in  a 
direction  opposite  to  that  in  which  it 
first  moved.  The  motion  of  a  pendulum, 
or  that  of  a  string  of  any  musical  instru- 
ment strained  tight  by  the  finger,  belongs 
to  this  class  of  motion. 

Oscillation,  Centre  of.  That  point  in 
an  oscillating  pendulum,  in  which  the 
whole  moving  force  is  concentrated,  and 
at  which,  if  it  meet  with  resistance,  it 
will  instantly  stop,  without  vibration  or 
strain  of  its  other  parts.  This  point  differs 
from  the  centre  of  gyration,  because  the 
motion  of  the  body  is  produced  by  the 
gravity  of  its  own  particles ;  whereas,  in 
gyration,  the  body  is  put  in  motion  by 
some  other  force,  acting  at  one  place 
only.     See  Percussion. 

OS'MELITE  (5fw>  to  smell).  A  mi- 
neral occurring  on  calcareous  spar,  mixed 
with  datholite,  and  emitting  at  the  ordi- 
nary temperature  of  a  room  a  distinct 
clayey  smell,  whence  its  name  is  derived. 

O'SMIUM  {banh>  odour).  A  metal 
discovered  in  1803,  in  the  grains  of  na- 
tive platinum,  together  with  iridium, 
and  named  from  the  pungent  and  pecu- 
liar smell  of  its  oxide. 

OSSEOUS  BRECCIA  (osseus,  bony). 
The  cemented  mass  of  fragments  of  bones 
of  extinct  animals  found  in  caverns  and 
fissures. 

OS'TIOLUM  (dim.  of  ostium,  a  door). 
A  little  door  ;  the  orifice  of  the  perithe- 
cium  of  some  fungaceous  plants. 

OSTRACEiE.  The  Oyster  tribe;  an 
order  of  the  Conchiferous  Mollusca, 
named  from  the  genus  ostrea,  in  which 
244 


the  two  halves  of  the  mantle  are  sepa- 
rated the  whole  way  round,  or  the  foot 
is  absent  or  very  small;  they  are  usually 
fixed  by  the  shell  to  solid  bodies. 

OSTRA'CILVE.  Oysters;  a  family  of 
the  atrachian  bivalves,  named  from  the 
genus  ostrea;  the  animal  is  sedentary, 
generally  affixed  by  the  under  valve ;  the 
shell  is  foliaceous,  rarely  pearly. 

OSTRACO'DA  (SarpaKov,  a  shell, 
eidor,  form).  A  family  of  the  Entomo- 
straca,  comprising  those  which  have  the 
shell  folded  so  as  to  resemble  those  of 
bivalves. 

OSTROTODA.  An  order  of  the  en- 
tomostracous  Crustacea,  in  which  the 
body  is  entirely  enclosed  under  a  large 
shield  having  the  form  of  a  bivalve  shell. 
The  animals  of  this  order  are  commonly 
termed  monoculous,  from  the  two  eyes 
being  united  into  one  mass. 

OTO'LOPHI  (oS?,  Atop,  the  ear,  \6- 
0o9,  a  crest).  A  group  of  Batrachians, 
which  have  the  muzzle  angular,  and  the 
head  furnished  on  each  side  with  a  crest 
which  extends  over  the  parotid  portion. 

OUTLIER.  A  term  applied  by  some 
mineralogists  to  a  portion  of  a  stratum 
which  occurs  at  some  distance,  detached 
from  the  general  mass  of  the  formation 
to  which  it  belongs. 

OVAL  {ovum,  an  egg).  A  curve  drawn 
by  taking  a  string  of  any  certain  length, 
and  fixing,  not  one  end  as  in  drawing 
the  circle,  but  both  ends  to  different 
points,  and  then  carrying  a  point  outside 
the  string,  always  keeping  it  stretched 
as  far  as  possible.  The  name  of  this 
figure  is  derived  from  its  resemblance  to 
the  transverse  section  of  an  egg.  Ellipses 
are  ovals  which  are  formed  by  the  above 
fixed  law,  but  the  latter  is  a  popular  term 
for  any  curved  figure,  approaching  to 
that  shape.  The  carpenter's  oval,  for 
example,  is  made  up  of  circular  arcs, 
which  unite  without  leaving  any  angular 
appearances  at  their  junctures. 

Ovals  of  Descartes.  These,  though  not 
Ellipses,  are  governed  by  a  determinate 
law,  which  constitutes  them  as  varieties 
of  that  curve.  As  in  the  Ellipse  the  two 
lines  drawn  from  the  foci  to  any  point  of 
the  circumference  vary,  so  that  the  in- 
crement of  one  shall  always  be  equal  to 
the  simultaneous  decrement  of  the 
others ;  so,  in  the  Cartesian  Ovals,  these 
increments  are  in  an  invariable  ratio. 
"  These  curves  may  therefore  be  defined 
the  locus  (place)  of  the  vertex  of  a  tri- 
angle, on  a  given  base,  one  of  whose 
sides  bears  a  given  ratio  to  the  sum  or 


0  vu 


OX  Y 


difference  of  a  given  line  and  the  other 
side." 

OVARIUM  OF  PLANTS.  The  hol- 
low case  at  the  hase  of  the  pistil,  enclosing 
the  ovules.  It  is  said  to  be  inferior, 
when  the  tube  of  the  calyx  contracts  ad- 
hesion with  its  sides ;  superior,  when  no 
such  adhesion  exists.  Hence,  an  infe- 
rior ovary  involves  a  superior  calyx;  a 
superior  ovary,  an  inferior  calyx.  When 
an  ovary  adheres  to  the  calyx  merely  by 
its  back,  it  is  termed  parietal. 

OVERLYING  ROCKS.  Interjected 
Rocks.  A  geological  term  applied  to 
those  rocks  which  appear  lying  over,  or 
interspersed  among,  the  stratified  rocks. 
They  are  probably  connected  with  de- 
posits situated  beneath  the  fundamental, 
having  apparently  been  ejected  in  a 
melted  state,  through  fissures  in  the 
strata. 

OVERSHOT  WHEEL.  A  water-wheel, 
to  which  the  water  is  conveyed  over  the 
top  of  the  wheel,  and  applied  above  the 
axle ;  in  this  case  the  water  acts  merely 
by  its  weight,  and  not  by  the  impulse  of 
the  stream. 

OVFGEROUS  {ovum,  an  egg,  gero,  to 
bear).  A  term  applied  to  parts  which 
contain  or  support  the  egg. 

OVI'PAROUS  (ovum,  an  egg,  pario, 
to  bring  forth).  A  designation  of  those 
animals,  which  produce  their  young  in 
an  egg,  the  egg  being  hatched  after  its 
exclusion  from  the  parent,  as  in  the 
cases  of  birds  and  most  reptiles. 

OVIPO'SITOR  {ovum,  an  egg,  pono, 
to  lay  down).  An  instrument  with  which 
some  Hymenopterous  insects  are  fur- 
nished for  depositing  their  eggs.  It  is 
formed  by  a  prolongation  of  the  last  seg- 
ment of  the  body  in  the  females,  and 
possesses  the  power  of  boring  a  hole  in 
certain  substances.  In  other  insects  of 
this  order,  the  ovipositor  is  replaced  by  a 
sting. 

OVO-VIVPPAROUS  {ovum,  an  egg, 
vivus,  alive,  pario,  to  bring  forth).  A 
designation  of  those  animals  which  bring 
forth  their  young  in  the  living  state,  the 
egg  having  been  previously  hatched 
within  the  body  of  the  parent. 

OVULE  OF  PLANTS.  A  small  pulpy 
body,  borne  by  the  placenta,  and  gra- 
dually changing  into  a  seed.  It  consists 
of  two  tunics  and  a  nucleus. 

OVU'LINjE.  The  egg-shells ;  the  sub- 
typical  group  of  the  Cyprceidce,  or  Cow- 
ries, named  from  the  genus  ovula,  and 
resembling  the  cowries  in  general  form  *, 
but  the  extremities  of  the  aperture  are 
245 


generally   produced,    and   there  are  no 
teeth  to  the  inner  lip. 

OXA'LIC  ACID.  An  acid  existing,  in 
the  form  of  an  acid  salt  of  potash,  in 
many  plants,  particularly  in  the  species 
of  Oxalis  and  Rumex ;  combined  with 
lime,  it  forms  a  part  of  several  lichens. 

OXALIDA'CEjE.  The  wood-sorrel 
tribe  of  Dicotyledonous  plants.  Herba- 
ceous plants,  undershrubs,  or  trees,  with 
leaves  alternate  ;  flowers  symmetrical ; 
stamens  hypogynous ;  fruit  capsular. 

O'XAMIDE.  A  white  insoluble  sub- 
limate, obtained  by  decomposing  oxalate 
of  ammonia  by  heat.  The  term  is  de- 
rived from  the  first  syllable  of  oxalic  acid 
and  ammonia. 

OXFORD  CLAY.  Clunch  clay;  a 
great  argillaceous  bed  interposed  between 
the  lower  and  the  middle  oolite.  It  is  of 
a  dark  blue  colour,  some  *of  the  beds  are 
bituminous,  and  abound  in  septaria,  or 
masses  having  internal  dissepiments.  In 
its  lower  part  are  beds  of  limestone  called 
Kelloway  Rock. 

OXIDA'TION.  The  process  of  con- 
verting metals  or  other  substances  into 
oxides,  by  combining  with  them  a  certain 
portion  of  oxygen.  It  differs  from  acidi- 
fication, in  the  addition  of  oxygen  not 
being  sufficient  to  form  an  acid  with  the 
substance  oxidated. 

O'XIDE.  A  generic  term,  consisting 
of  the  first  syllable  of  oxygen  with  a  termi- 
nation indicative  of  combination,  applied 
to  compound  neutral  bodies  and  bases.  To 
this  the  name  of  the  other  element  is 
joined,  to  express  the  specific  compound. 
Thus,  a  compound  of  oxygen  and  hydro- 
gen is  oxide  of  hydrogen ;  if  oxygen  and 
potassium,  oxide  of  potassium  ;  of  which 
compounds  the  first,  or  water,  is  an  in- 
stance of  a  neutral  oxide ;  the  second,  or 
potash,  of  a  base  or  alkaline  oxide.  But 
the  same  elementary  body  often  com- 
bines with  oxygen  in  more  than  one 
proportion,  forming  two  or  more  oxides  ; 
to  distinguish  them,  the  following  pre- 
fixes are  employed  : — 

1.  Proto  (upSi-or,  first),  denoting  the 
minimum  of  oxygen,  as  protoxide. 

2.  Deuto  (aeurepoc,  second),  denoting 
a  second  proportion,  as  dioxide.  This 
is  also  called  bin- oxide. 

3.  Trito  {rplrof,  third),  denoting  a 
third  proportion,  as  tritoxi&e.  This  is 
also  called  ter-oxide. 

4.  Per  {very  much),  denoting  the  max- 
imum of  oxidation,  as  peroxide. 

OXY  (ofv?,  acid).    A  prefix,  denoting 
in  some  terms,  the  presence  of  acidity; 
M3 


P  AI 


PAL 


in  others,  the  presence  of  oxygen ;  in  a 
third  class  of  terms,  acuteness  of  sense 
or  function ;  and,  lastly,  sharp-pointed- 
ness. 

O'XYGEN  (b£i>s,  acid,  yevvda,  to  gene- 
rate). The  name  given  by  Lavoisier  to 
an  elementary  body,  with  reference  to  its 
property  of  forming  acids  with  other  ele- 
mentary bodies.  Oxygen  is  a  permanent 
gas,  when  uncombined,  and  forms  one- 
fifth  part  of  the  atmospheric  air.  By 
Priestley  it  was  called  dephlogisticated 
air ;  by  Scheele,  empyreal  air ;  by  Con- 
dorcet,  vital  air. 

O'XYSTOMES  (6fi»r,  sharp,  o-To/xa,  a 
mouth).      The   name   given   by  Milne 


Edwards  to  the  fourth  and  last  family  of 
brachyurous  crustaceans,  comprising  all 
those  species  which  most  resemble  the 
type,  especially  in  the  conformation  of 
the  buccal  apparatus. 

O'ZON  (6'£a>,  to  smell).  The  name 
given  by  Schbnbein  to  the  odorous  prin- 
ciple emitted  during  the  action  of  an 
electrical  machine.  He  considered  it  to 
be  a  body  contained  both  in  air  and  in 
water;  that  it  had  hitherto  escaped  the 
observation  of  chemists  ;  and  that,  under 
certain  circumstances,  it  was  set  free  by 
electricity.  It  is  probably  a  trit-oxide  of 
hydrogen. 


PACHYCEPHALI'NjE  (iraxwp,  thick, 
KecpaXr],  head).  The  name  given,  in 
Mr.  Swainson's  classification  of  birds,  to 
the  Great-headed  Chatterers,  the  second 
sub-family  of  the  Ampelidae,  or  Chat- 
terers. 

PACHYDE'RMATA  {va%w,  thick, 
iepfxa,  skin).  An  order  of  the  Mammalia, 
comprising  thick-skinned  animals,  as  the 
elephant,  the  rhinoceros,  &c,  and  certain 
aquatic  animals,  approaching  to  the  hip- 
popotamus. 

PACKFONG.  The  white  copper  of 
the  Chinese,  said  to  be  an  alloy  of  copper, 
nickel,  and  zinc.  It  is  also  called  Ger- 
man Silver. 

PA'GINA.  Literally,  a  page  of  a  book ; 
hence,  applied  to  a  surface  of  a  leaf, 
pagina  superior  being  the  upper,  pagina 
inferior  the  lower  surface. 

PA'GODITE.  A  species  of  steatite  or 
serpentine,  which  the  Chinese  carve  into 
figures. 

PAGU'RIANS.  A  tribe  of  anomour- 
ous  crustaceans,  named  from  the  genus 
pagurus,  and  known  by  the  popular 
names  of  Hermit-crabs  and  Soldier-crabs ; 
in  France  they  are  called  Bernards 
l'Hermite. 

PAIRS,  CHEMICAL.  In  the  un- 
organized kingdom  the  elementary  sub- 
stances are  generally  combined  by  the 
force  of  affinity,  either  two  and  two  in 
pairs,  or  the  pairs  themselves  forming 
doublepairs,  and  in  some  few  cases  even 
the  double  pairs  united.  In  the  organ- 
ized kingdom,  on  the  contrary,  the  four 
elements  do  not  enter  into  binary,  but  at 
246 


least  into  ternary,  or  quaternary  combi- 
nations, without  first  forming  pairs. 

PALiEO'GRAPHY  {iraXcubs,  ancient, 
ypd<p<o,  to  write).  The  study  of  ancient 
documents,  including  the  knowledge  of 
the  various  characters  used  at  different 
periods  by  the  writers  and  sculptors  of 
different  nations  and  languages,  their 
abbreviations,  initials,  &c. 

PALjEONTO'LOGY(7ra\cu69,  ancient, 
ovra,  beings,  \6fos,  an  account).  The 
science  which  treats  of  fossil  remains, 
both  animal  and  vegetable;  of  their 
forms  and  relations,  of  the  changes  which 
they  have  undergone,  and  of  the  causes 
which  have  produced  their  immersion  in 
the  strata. 

PALjEOSAU'RUS  (TraXcuo?,  ancient, 
aavpa,  a  lizard).  The  name  of  a  genus 
of  fossil  Saurians  discovered  in  the  mag- 
nesian  conglomerate  on  Durdham  Down, 
near  Bristol,  in  1834. 

PALiEOTHE'RIUM  (nakaib?,  ancient, 
Qnplov,  a  wild  beast).  A  fossil  extinct 
quadruped,  belonging  to  the  order  Pachy- 
dermata,  resembling  a  pig,  or  tapir,  but 
of  great  size. 

PALjEOZO'IC  SERIES  {iraXaid  £5a, 
ancient  animals).  A  name  given  to  the 
fossiliferous  strata  of  earlier  geological 
date  than  the  carboniferous  system,  and 
the  mountain  limestone,  with  reference 
to  their  organic  contents.  The  term 
Protozoic  has  been  applied  to  these  early 
groups  of  strata;  but  this  term,  it  has 
been  observed,  seems  to  assert  more  than 
is  necessary,  perhaps  more  than  is  known. 

PALEA.    Chaff.    The  term  paleee  is 


PAL 


PAP 


applied  to  the  minute  colourless  bracts 
at  the  base  of  the  florets  of  a  capitulum ; 
and  to  the  floral  envelope  of  grasses, 
which  immediately  surrounds  the  sexual 
organs. 

Paleaceous.  Chaffy  ;  covered  with  pa- 
leae,  or  membranous  scales,  as  the  recep- 
tacle of  some  compositas. 

PALLADIUM.  A  new  metal  found 
by  Wollaston  in  the  ore  of  platinum. 

PALLAS  or  OLBERS.  A  telescopic 
planet,  discovered  by  Dr.  Olbers,  in  1802, 
and  situated  in  the  solar  system  between 
Mars  and  Jupiter.  Its  diameter  is  un- 
known. It  describes  its  orbit  round  the 
sun  in  four  years,  seven  months,  and 
eleven  days.  Its  distance  from  the  sun 
is  267  millions  of  miles. 

PA'LLIAL  IMPRESSION.  The  mark 
formed  in  a  bivalve  shell  by  the  pallium 
or  mantle.  It  occurs  usually  near  the 
margin  of  the  shell,  and  is,  hence,  some- 
times called  the  marginal  impression.  In 
the  Dimyaria,  this  mark  passes  from  one 
impression  of  the  muscles  of  attachment 
to  the  other ;  if,  in  its  passage,  it  bends 
inwards  posteriorly,  it  is  said  to  be  sinu- 
ated,  and  the  part  where  this  occurs  is 
the  siphonal  scar  of  Mr.  Gray. 

PA'LLIOBRANCHIA'TA  {pallium,  a 
mantle,  branchice,  gills).  A  term  ori- 
ginally proposed  by  Blainville  for  the 
Brachiopodous  mollusca,  notwithstanding 
his  belief  that  the  spiral  arms  were  the 
organs  of  respiration.  It  has  since  been 
proved  by  Owen  to  be  strictly  appropriate, 
and  is  applied  by  him  to  the  class  of  ace- 
phalous mollusca,  in  which  the  gills  are 
developed  from  the  mantle. 

PALMA'CEjE.  The  Palm  tribe  of 
Monocotyledonous  plants.  Plants  with 
an  arborescent  trunk,  covered  with  the 
sheathing  bases  of  leaves ;  leaves  termi- 
nal, clustered,  pinnate,  or  flabelliform ; 
flowers  hexapetalo'ideous,  stamens  defi- 
nite; ovarium  superior,  3-celled ;  fruit 
baccate,  or  drupaceous,  with  fibrous 
flesh. 

PALMATE  LEAF.  A  form  of  leaf, 
having  five  lobes,  with  the  midribs  radi- 
ating from  a  common  point  at  the  base  of 
the  leaf,  and  resembling  the  palm  of  the 
hand.  The  palmate  leaf  admits  of  the 
following  varieties,  which  occur,  in  bota- 
nical descriptions : — 

1.  Palmatifid,  in  which  the  lobes  are 
divided  as  far  down  as  half  the  breadth 
of  the  leaf. 

2.  Palmatilobate,  in  which  the  lobes 
are  divided  to  an  uncertain  depth. 

3.  Palmatipartite,  in  which  the  lobes 

247 


are  divided  beyond  the  middle,  and  the 
parenchyma  is  not  interrupted. 

4.  Palmatisected,  in  which  the  lobes 
are  divided  down  to  the  midrib,  and  the 
parenchyma  is  interrupted. 

PALMI'PEDES  (palma,  the  palm  of 
the  hand,  pes,  the  foot).  Natatores. 
Swimmers  ;  an  order  of  web-footed  birds, 
capable  of  swimming  in  the  water  the 
instant  they  are  liberated  from  their  egg- 
coverings.  They  comprehend  the  divers, 
pelicans,  albatrosses,  swans*,  &c. 

PA'LPI  {palpo,  to  touch).  The  organs 
of  touch  developed  from  the  labium  and 
maxillae  of  insects,  commonly  called 
feelers. 

PALPICO'RNES  {palpi,  feelers,  cornu, 
a  horn).  A  family  of  the  pentamerous 
Coleoptera,  characterized  by  the  presence 
of  antennae  with  club-like  terminations, 
which  are  usually  shorter  than  one  of  the 
pairs  of  palpi.    They  are  mostly  aquatic. 

PANDURIFORM  {pandura,  the  an- 
cient shepherd's  pipe,  forma,  likeness). 
Fiddle-shaped ;  obovate,  with  a  deep 
sinus  on  each  side,  as  the  leaves  of  rumex 
pulcher. 

PA'NGOLINS.  A  common  designa- 
tion of  the  Scaly  Ant-eaters,  derived 
from  a  Javanese  word  signifying  an  ani- 
mal which  rolls  itself  into  the  form  of  a 
ball.  The  pangolins  correspond  with  the 
genus  Manis  of  Linnaeus. 

PANICLE  {panicula,  the  woof  wound 
round  the  quill  in  the  shuttle).  A  form 
of  inflorescence,  in  which  the  flower-buds 
of  a  raceme  have,  in  elongating,  developed 
other  flower-buds,  as  in  the  oat.  When 
the  rachis  of  inflorescence  separates  irre- 
gularly into  branches,  so  as  to  lose  the 
form  of  an  axis,  this  is  called  by  Willde- 
now  a  deliquescent  panicle. 

PANTOCHRONO'METER  (war,  irav- 
top,  all,  xpovo^,  time,  fierpov,  a  measure). 
An  instrument  which  combines  the  use 
of  the  compass,  of  the  sun-dial,  and  of 
the  universal  time-dial. 

PAPAVERACEjE.  The  Poppy  tribe 
of  Dicotyledonous  plants.  Herbaceous 
plants  with  leaves  divided,  alternate ; 
flowers  polypetalous,  single  on  long  pe- 
duncles ;  petals  4,  or  some  multiple  of  4, 
cruciate  ;  stamens  hypogynous  ;  ovarium 
solitary ;  seeds  numerous. 

PAPER  COAL.  A  bituminous  shale, 
which  separates  into  thin  laminae  of 
coal,  like  sheets  of  paper. 

PAPILIONACEOUS  {papilio,  a  but- 
terfly). A  form  of  corolla  resembling  a 
butterfly,  and  found  in  all  the  leguminous 
plants  of  Europe.  Of  the  five  petals,  the 
M4 


PAR 


PAR 


uppermost  is  dilated,  and  called  vexillum, 
or  the  standard  ;  the  two  lateral  are  con- 
tracted and  parallel,  and  called  alee,  or 
the  wings ;  the  two  lower  are  contracted, 
parallel,  generally  coherent  by  their  an- 
terior margin,  and  termed  carina,  or  the 
keel. 

PAPPUS  (irdinros,  the  down  of  the 
cheek).  A  botanical  term  for  the  feathery 
appendage  which  crowns  the  fruit  of 
many  composite  plants,  being,  in  fact,  a 
reduced  calyx.  A  familiar  instance  oc- 
curs in  the  down  of  the  dandelion. 

PARA-  (napd).  A  Greek  preposition 
■with  various  meanings,  as  through,  near, 
about,  &c.  In  some  chemical  compounds, 
it  denotes  near  to,  and  expresses  a  close 
alliance  between  two  compounds. 

PARA'BOLA  (napafioXri,  the  Conic 
Section  parabola,  so  named  because  its 
axis  is  parallel  to  the  side  of  the  cone). 
A  section  of  a  cone  by  a  plane  parallel 
to  one  of  its  sides ;  it  is  therefore  an  open 
curve,  which  would  spread  out  wider  and 
wider,  if  the  cone  were  extended.  A 
simple  illustration  of  the  parabola  is  the 
curved  line  described  by  a  body  thrown 
forward,  as  of  a  bullet  from  a  gun,  a  jet 
of  water  from  a  fire-engine,  &c. 

Paraboloid.  A  geometrical  solid,  formed 
by  the  revolution  of  a  parabola  round  its 
axis  (See  Conoid).  The  term  is  also 
applied  to  two  surfaces  of  the  second  de- 
gree, viz.  the  elliptic  paraboloid  and  the 
hyperbolic  paraboloid,  which  answer  to 
the  curve  parabola. 

PARACE'NTRIC  VELOCITY.  An 
expression  denoting  the  rate  at  which  a 
moving  body  approaches  a  certain  centre, 
without  reference  to  the  rate  at  which  it 
moves  in  space. 

PARACEPHALO'PHORA  {napd,  be- 
side, Ke<t>a\ri,  the  head,  0<?po>,  to  carry). 
The  name  given  by  De  Blainville  to  a 
class  of  molluscous  animals,  in  which 
the  head  is  but  little  distinct  from  the 
body,  but  is  always  provided  with  some 
of  the  organs  of  sense.  They  are  divided 
into  the  sub-classes  dioica,  monoica,  and 
hermaphrodita. 

PARADI'SIDjE.  The  Birds  of  Para- 
dise ;  a  family  of  the  Insessores,  or 
Perchers,  characterized  by  the  extraor- 
dinary development  of  their  feathers. 
They  are  confined  to  New  Guinea  and 
the  neighbouring  islands.  See  Tenui- 
rostres. 

PA'RADOX  (7rapa3o?ta,  marvellous- 
ness).  A  statement  which  is  opposed 
to  general  belief,  being,  at  its  first  enun- 
ciation, apparently  contradictory  of  some 


established  maxim  or  truth.  Thus,  "  the 
wise  man  alone  is  rich,"  is  a  paradox, 
for  the  statement  would  be  ridiculed  by 
all,  except  the  wise. 

PA'RAFFIN.  Petroline.  A  particular 
hydrocarbon  produced  in  the  distillation 
of  wood.  Its  name  is  derived  from  pa- 
rum  afflnis,  denoting  its  remarkable  in- 
difference to  other  bodies  in  a  chemical 
point  of  view. 

PARALLACTIC  INSTRUMENT. 
Ptolemy's  Rules.  An  astronomical  in- 
strument invented  by  Ptolemy  for  deter- 
mining the  moon's  parallax,  and  described 
in  his  Almagest. 

PA'RALLAX  (ffapdWa&v,  alterna- 
ation).  Parallax  may  be  generally  defined 
to  be  the  change  of  the  apparent  situ- 
ation of  an  object  arising  from  a  change 
of  the  real  situation  of  the  observer.  In 
astronomical  language,  the  word  has  a 
more  technical  meaning,  and  is  restricted 
to  the  difference  of  the  apparent  positions 
of  any  celestial  object  when  viewed  from 
a  station  on  the  surface  of  the  earth, 
and  from  its  centre.  The  centre  of  the 
earth  is  the  general  station  to  which  all 
astronomical  observations  are  referred : 
but,  as  we  observe  from  the  surface,  a 
reduction  to  the  centre  is  needed;  and 
the  amount  of  this  reduction  is  called 
parallax. 

1.  Parallax,  diurnal  and  annual.  By 
the  preceding  paragraph  it  is  plain  that 
the  parallax  of  a  body  signifies  the  differ- 
ence between  its  apparent  place  and  its 
true  place,  or  that  in  which  it  would  be 
seen,  if  the  observer  were  situated  at  the 
centre  to  which  the  motion  is  referred. 
When  the  point  of  reference  is  the  centre 
of  the  earth  itself,  the  change  of  aspect 
is  called  the  diurnal  parallax ;  when  it 
is  the  centre  of  the  earth's  orbit,  the 
change  is  called  the  annual  parallax,  or 
parallax  of  the  great  orb.  The  latter  is 
the  angle  under  which  the  semidiameter 
of  the  earth's  orbit  would  be  seen  from  a 
superior  planet,  or  from  a  fixed  star. 

2.  Parallax,  horizontal.  The  parallax 
changes  with  the  planet's  distance  from 
the  earth,  and  also  with  its  altitude  above 
the  horizon.  It  is  nothing  when  the 
planet  is  in  the  zenith ;  and  greatest,  the 
distance  .from  the  earth  remaining  the 
same,  when  the  planet  is  in  the  horizon. 
In  the  latter  case,  it  is  called  horizontal 
parallax.  Thus,  by  saying  that  the 
moon's  horizontal  parallax  is  58'  on  a 
certain  day,  we  mean  that  the  moon's 
distance  is  such,  that  if  she  were  in  the 
horizon  of  any  place,  the  spectator's  de- 


PAR 


PAR 


scent  to  the  centre  of  the  earth  would 
elevate  her  58'  above  the  rational  horizon 
drawn  through  the  centre. 

3.  Parallax,  angle  of.  In  Optics,  the 
angle  of  parallax  is  that  angle  which  the 
axes  of  the  eyes,  when  directed  towards 
an  object,  form  with  it  at  their  point  of 
contact.  This  angle  becomes  greater  as 
the  object  is  nearer. 

PARALLELE'PIPED  (irapaWtiKeni- 
•rredov,  a  body  with  parallel  surfaces).  A 
hexahedron,  all  whose  faces  are  paral- 
lelograms, and  each  pair  of  faces  which 
do  not  actually  intersect  are  parallel.  A 
prism  whose  bases  are  parallelograms  is 
called  a  parallelepiped.  If  the  bases  of 
a  rectangular  parallelepiped  be  squares, 
and  the  attitude  be  equal  to  the  side 
of  the  base,  all  its  faces  will  be  squares, 
and  such  a  parallelepiped  is  called  a  cube. 

PARALLE'LOGRAM  (napaWtiXo- 
7pa.niJ.0s,  bounded  by  parallel  lines).  A 
quadrilateral  figure,  whose  opposite  sides 
are  parallel.  The  term,  as  thus  defined, 
is  applicable  to  the  square,  the  rectangle 
or  oblong,  the  rhombus  or  lozenge,  and 
the  rhomboid ;  but  these  terms  are  sig- 
nificant of  relations  existing  between  the 
angles,  as  well  as  the  sides  of  the  figures. 

PARALLELS  (napaWtjXos,  beside 
one  another,  side  by  side).  In  Astro- 
nomy, the  term  Parallels  denotes  those 
circles  which  every  point  of  the  earth 
between  its  poles  describes  by  its  diurnal 
rotation,  and  which  run,  as  it  were,  side 
by  side  of  one  another. 

Parallels  Mathematical.  Parallel  right 
lines  are  such  as  are  in  the  same  plane, 
and  which,  being  produced  continually 
in  both  directions,  would  never  meet. 

PARA'METER  {irapafxerpeu),  to  mea- 
sure by,  or  with,  another  thing).  A  term- 
originally  applied  to  a  constant  straight 
line  belonging  to  each  of  the  conic  sec- 
tions, and  synonymous  with  latus  rec- 
tum; that  is,  the  perpendicular  drawn  to 
the  axis  through  a  focus,  terminated  both 
ways  by  the  curve,  was  the  parameter  of 
the  curve.  The  term  was  afterwards 
applied,  in  a  general  sense,  to  the  con- 
stant quantity  which  enters  into  the 
equation  of  a  curve.  In  the  language  of 
astronomy,  what  were  formerly  called 
the  parameters  of  the  orbits,  are  now 
generally  called  their  elements. 

PARASI'TA.  The  Louse  tribe;  an 
order  of  "  familiar  "  insects,  which  are 
entirely  wingless,  do  not  undergo  meta- 
morphosis, but  agree  with  the  true  in- 
sects in  having  only  six  legs.  The  term 
parasite,  derived  from  irapa,  and  (m-or, 
249 


provisions,  denotes,  in  its  original  sense, 
a  hanger-on  at  the  tables  of  the  great. 

PARATO'NNERE.  The  French  term 
for  a  lightning  conductor,  or  metallic  rod, 
made  to  project  above  the  highest  part 
of  a  building,  and  continued  down  to  the 
ground ;  its  object  being  to  promote  the 
discharge  of  an  electric  cloud,  and  to 
conduct  the  lightning  to  the  ground 
without  injuring  the  building. 

PARE'NCHYMA  (napeyxv^a,  any 
thing  poured  in  beside).  The  name  given 
by  Erasistratus  to  the  peculiar  substance 
of  the  lungs,  liver,  kidneys,  and  spleen, 
as  if  formed  separately  by  the  blood  of 
veins  which  run  into  those  parts  :  the 
word  o-apf  he  used  only  of  the  muscular 
flesh.  The  term  is  generally  applied  to 
the  soft  tissue  of  organs,  in  plants  and 
animals,  particularly  to  that  of  the 
glands. 

PARHE'LION  {napa,  near,  »j\<or,  the 
sun).  A  mock  sun,  or  meteor,  of  a 
brilliant  light,  resembling  the  sun,  and 
occasionally  accompanying  halos.  The 
term  parhelion  denotes  an  image  of  the 
sun  formed  by  reflection  from  a  cloud. 

PARIE'TAL  (paries,  a  wall).  A  term 
applied  to  any  thing  which  is  attached  to 
the  wall  of  an  organ,  as  to  the  placenta 
of  plants,  when  attached  to  the  walls  of 
the  ovary,  as  in  poppy,  violet,  &c. 

PA'RINjE  {parus,  the  tit).  Parine 
birds  or  Tits  ;  a  family  of  the  Cantatrices 
of  Macgillivray,  somewhat  allied  to  the 
kinglets  and  the  jays,  although,  from 
their  diminutive  size,  they  seem  at  first 
sight  to  have  little  affinity  to  the  latter. 

PARI-PINNATE.  Equally  pinnate, 
abruptly  pinnate;  applied  to  a  pinnate 
leaf  of  which  the  petiole  is  terminated 
neither  by  a  leaflet  nor  a  tendril. 

PARO'NYMOUS  WORDS  {napthw- 
fxos,  formed  from  a  word  by  a  slight 
change).  Words  which  belong  to  one 
another,  as  the  substantive,  adjective, 
verb,  &c.  of  the  same  root.  These  have 
not  in  every  case  a  precisely  corre- 
spondent meaning,  and  the  careless  or 
designed  application  of  them  may  lead  to 
the  logical  fallaciafigurce  dictionis,  which 
properly  belongs  to  the  case  of  Ambi- 
guous Middle.  Thus,  "  Projectors  are 
unfit  to  be  trusted :  this  man  has  formed 
a  project ;  therefore  he  is  unfit  to  be 
trusted."  Here  the  sophist  proceeds  on 
the  hypothesis  that  he  who  forms  a,  pro- 
ject must  be  a  projector:  whereas  the 
bad  sense  which  commonly  attaches  to 
the  latter  word,  is  not  at  all  implied  in 
the  former.     Whately. 

M5 


PEA 


PEC 


PART,  LOGICAL.  Logically,  species 
are  called  parts  of  the  genus  they  come 
under ;  and  individuals,  parts  of  the 
species.  Really,  the  genus  is  a  part  of 
the  species  ;  and  the  species,  of  the  indi- 
vidual. 

PA'RTICIPLE.  A  part  of  speech  said 
to  have  derived  its  name  from  its  par- 
taking of  the  nature  both  of  the  verb  and 
of  the  noun.  Home  Tooke  calls  it  a  u  verb 
adjective." 

PA'RTICLE  {particula,  a  little  part). 
The  term  applied  by  grammarians  to 
those  parts  of  speech  which  are  inde- 
clinable, and  are  neither  nouns  nor  verbs, 
but  express  the  relations,  connexions, 
and  modifications  of  ideas.  In  this  sense, 
particles  comprehend  adverbs,  conjunc- 
tions, prepositions,  and  interjections. 

PARTICULAR  PROPOSITION.  In 
Logic,  a  proposition  in  which  the  predi- 
cate is  affirmed  or  denied  of  some  part 
only  of  the  subject. 

PARTITE  LEAF.  In  Botany,  a  leaf 
is  so  called  when  it  is  parted  or  divided 
into  a  fixed  number  of  segments,  which 
are  separated  nearly  down  to  the  base ;  a 
leaf  with  two  such  divisions  is  said  to  be 
bipartite ;  with  three,  tripartite ;  with 
many,  pluripartite,  &c. 

PASSERFNuE  {passer,  a  sparrow). 
Passerine  birds  or  sparrows ;  a  family  of 
the  Deglubitrices  of  Macgillivray,  differ- 
ing little  from  the  Emberizinaa  of  that 
author,  except  in  the  form  of  the  bill, 
and  in  having  the  upper  mandible  broad 
and  concave,  instead  of  being  narrow 
and  furnished  with  a  prominent  knob. 
By  other  writers,  the  Passerine  birds  are 
included  in  the  Fringilladae  or  Finches, 
a  family  of  the  Insessores  or  Perchers. 

PATENT  YELLOW.  A  pigment  con- 
sisting of  chloride  and  protoxide  of  lead  ; 
also  called  mineral  yellow. 

PAVO.  The  Peacock ;  a  modern 
southern  constellation,  consisting  of  four- 
teen stars,  and  occupying  a  part  of  the 
space  situated  between  Sagittarius  and 
the  South  Pole. 

PAVO'NIDjE  {pavo,  the  peacock). 
The  Peacock  family,  the  first  family  of 
Rasorial  birds,  in  Mr.  Swainson's  ar- 
rangement. The  term  Phasianidce  is 
adopted  by  other  writers. 

PEA  IRON-ORE.  The  common  name 
of  the  pisiform  variety  of  argillaceous  or 
clay  iron-stone. 

PEA-STONE.  Pisiform  limestone ;  a 
sub-species  of  limestone,  occurring  in 
round  granular  concretions. 

PEAK.  When  the  summit  of  a  moun- 
250 


tain  rises  with  an  acclivity  more  abrupt 
than  the  rest  of  the  mountain,  it  is 
usually,  whether  conical  or  not,  called 
a  peak.  When  very  slender  pointed 
rocky  protuberances  form  the  summits, 
they  are  called  by  the  French  aiguilles, 
or  needles,  but  by  us  generally  peaks. 

PEAR  GAGE.  An  instrument  in- 
vented by  Smeaton  for  measuring  the 
degree  of  the  rarefaction  of  air,  and 
named  from  its  peculiar  form.  It  is  a 
modification  of  the  air-pump  gage. 

PEARL.  A  spherical  concretion 
formed  within  the  pearl  oyster,  consist- 
ing of  carbonate  of  lime  and  albumen. 
Sir  Everard  Home  considered  that  the 
abortive  ova  of  the  animal  were  the  nu- 
clei upon  which  the  pearls  were  formed. 

PEARL-ASH.  The  name  of  potash 
when  it  is  calcined,  and  of  a  whitish 
pearly  lustre.  It  is  employed  in  making 
flint  glass,  soap,  &c. 

PEARL-SINTER.  Fiorite.  A  variety 
of  stalagmitic  quartz  or  quartzsinter, 
found  at  Santa-Fiora  in  Tuscany,  &c. 

PEARL-SPAR.  Another  name  for 
brown-spar  or  sidero-calcite.  It  consists 
of  the  carbonates  of  lime  and  magnesia, 
with  traces  of  other  substances,  and  oc- 
curs abundantly  in  the  lead  mines  in 
the  north  of  England,  &c. 

PEARL-STONE.  A  sub-species  of  in- 
divisible quartz,  occurring  in  large  beds 
in  clay,  porphyry,  and  secondary  trap- 
rocks,  in  Hungary  and  in  Spain. 

PEARL-WHITE.  The  sub-nitrate  of 
bismuth,  formerly  called  Magistery  of 
bismuth.  From  the  nitric  solution  of 
bismuth  is  procured  a  powder  of  a  pearly 
lustre,  used  by  perfumers  under  the 
name  of  pearl  powder. 

PEAT  or  TURF.  A  carboniferous  de- 
posit formed  in  the  low  parts  of  plains 
by  the  gradual  decomposition  of  succes- 
sive layers  of  vegetables,  burning  with 
flame  and  grey  smoke,  and  emitting  a 
pungent  and  somewhat  fetid  odour.  It 
occurs  wherever  the  soil  has  been  Jong 
soaked  with  water,  which  has  no  means 
of  complete  evaporation. 

PE'CHBLENDE.  An  ore  of  uranium, 
in  which  the  metal  exists  in  the  state  of 
sulphuret. 

PE'CORA  (plur.  of  pecus,  cattle).  The 
fifth  order  of  the  Mammalia  in  the  sys- 
tem of  Linnaeus,  where  they  are  placed 
between  the  orders  glires  and  bellute. 

PECTIC  ACID  (7r»KTi9,  a  coagulum). 
A  substance  obtained  from  the  carrot 
and  other  vegetables,  so  named  from  its 
remarkable  tendency  to  gelatinize. 


PED 


PEL 


PECTIN  {irriKrh,  a  coagulum).  The 
name  given  by  Braconnot  to  a  principle 
which  forms  the  basis  of  vegetable  jelly. 

PE'CTINATE  (pecten,  a  comb).  In 
Botany,  a  term  expressing  a  modification 
of  the  pinnatifid  leaf,  in  which  the  seg- 
ments are  long,  close,  and  narrow,  like 
the  teeth  of  a  comb. 

PE'CTINATED  (pecten,  a  comb). 
Having  processes  resembling  in  form  and 
arrangement  the  teeth  of  a  comb,  as  the 
spines  of  some  species  of  murex. 

PE'CTINIBRANCHIA'TA(p<?cten,  pec- 
tinis,  a  comb,  branchice,  gills).  The  name 
of  the  sixth,  the  most  highly  organized 
and  the  most  numerous  order  of  Gastero- 
pods,  including  all  the  inhabitants  of 
spiral  univalve  sea-shells,  and  many  with 
shells  simply  conical,  which  have  their 
comb-shaped  gills  placed  internally  in  a 
capacious  cavity,  into  which  the  water  is 
freely  admitted. 

PECTI'NIDiE.  A  tribe  of  Monomy- 
arian  conchifers,  including  the  pectens, 
the  limae,  the  oysters,  &c. 

PECTORA'LES  PEDU'NCULATI.  A 
family  of  Acanthopterygious  fishes,  in 
which  the  pectoral  fins  are  attached  to 
the  bones  by  a  peduncle,  resembling  a 
wrist,  enabling  the  fish  to  leap  in  pursuit 
of  its  prey,  as  in  the  lophius,  or  fishing- 
frog. 

PE'DAL  (pes,  pedis,  a  foot).  A  foot- 
key  in  musical  instruments,  or  a  lever 
for  acting  on  the  swell  of  the  organ  or 
the  piano-forte.  A  pedal-base  is  a  base 
which  remains  stationary  on  one  note, 
while  the  other  parts  continue  to  move 
and  form  various  chords  which  are  re- 
lated to  the  pedal-base  according  to  the 
laws  of  harmony. 

PED  ATE.  A  botanical  designation  of 
that  form  of  the  palmate  leaf,  in  which 
the  two  lateral  lobes  are  themselves  sub- 
divided, as  in  helleborus  niger.  The 
same  modifications  occur  as  in  the  pal- 
mate leaf,  with  similar  terms,  as  peda- 
tifid,  pedatipartite,  pedatisected,  and  pe- 
datilobate. 

PEDICELLA'RLE  (pedicellus,  a  little 
stalk).  The  name  of  certain  appendages 
to  the  integument  of  the  Echini  and 
other  echinodermata,  consisting  of  a 
dilated  end  or  head,  usually  prehensile, 
supported  by  a  slender  stem  or  pedicel. 
They  have  been  distinguished  by  Valen- 
tin into  the  gemmiform,  the  tridactyle, 
and  the  snake-headed,  or  ophicephalous. 

PEDIPA'LPI  (pes,  pedis,  a  foot,  palpi, 
the  organs  of  touch  in  insects).    A  divi- 
sion of  the  Arachnida,  in   which   the 
251 


palpi  are  exceedingly  strong,  and  fur- 
nished at  their  extremity  with  a  prehen- 
sile forceps,  as  in  the  scorpion. 

PEDO'METER  (nedov,  the  ground, 
/jLerpov,  a  measure).  An  instrument 
for  measuring  the  distance  which  a  person 
has  performed  by  walking  or  riding.  It 
is  of  a  portable  size,  and  its  operation 
is  effected  by  motion  communicated  to 
its  machinery  by  the  traveller  him- 
self. 

PE'DUNCLE  and  PE'DICEL.  In 
botanical  language,  the  peduncle  is  that 
part  of  the  inflorescence  which  proceeds 
immediately  from  the  stem.  If  it  is 
divided,  its  principal  divisions  are  called 
branches  ;  and  its  ultimate  ramifications, 
which  bear  the  flowers,  are  named  pedi- 
cels. There  are  modifications  of  the 
peduncle,  to  which  other  names  are  ap- 
plied.    See  Rachis  and  Scape. 

PEDU'NCULATE  (pedunculus,  a  foot- 
stalk). That  which  is  supported  on  a 
peduncle,  or  foot-stalk,  as  the  shell  of 
Terebratula,  or  a  flower  furnished  with  a 
stalk.     See  Sessile. 

PE'GASUS.  The  Flying  Horse ;  one 
of  the  old  northern  constellations,  con- 
sisting of  eighty-nine  stars. 

PE'GMATITE.  A  granular  mixture 
of  quartz  and  felspar.  It  often  occurs 
in  granite  veins  and  passes  into  Graphic 
Granite,  from  which  some  geologists  do 
not  distinguish  it. 

PELECA'NIDjE.  The  Pelican  tribe  ; 
a  family  of  the  Natatores,  or  Swimming 
birds,  characterized  by  having  the  hind 
toe  united  by  membrane  to  the  rest. 
They  are,  nevertheless,  almost  the  only 
birds  of  the  order  which  perch  upon 
trees.  They  include  the  pelican,  the 
cormorant,  the  frigate-bird,  the  gannet, 
and  the  boobie. 

PELIO'MA.  Iolite.  A  blue-coloured 
mineral,  belonging  to  the  garnet  tribe, 
now  commonly  called  dichroite,  from  its 
exhibiting  two  different  colours  when 
viewed  in  different  positions. 

PELLICLE  (dim.  of  pellis,  the  skin 
or  hide  of  a  beast,  flayed  off).  A  thin 
skin,  or  film.  Among  chemists,  it  de- 
notes a  thin  surface  of  crystals  uniformly 
spread  over  a  saline  liquor  evaporated  to 
a  certain  degree. 

PE'LOKONITE.  An  amorphous  mi- 
neral, of  a  bluish-black  colour,  contain- 
ing phosphoric  acid,  iron,  manganese, 
and  copper. 

PE'LTATE  (pelta,  a  shield).  Shield- 
shaped;  a  term  applied  by  botanists  to 
leaves  which  are  fixed  to  the  petiole  by 
M6 


PEN 


PER 


their  centre,  or  by  some  point  within  the 
margin,  as  in  tropaeolum. 

PE'NCIL  {penicillus,  any  thing  which 
has  its  end  divided  like  a  painter's  brush). 
In  optics,  a  pencil  of  rays  is  a  collection 
of  rays  which  converge  to,  or  diverge 
from,  a  point ;  in  geometry,  a  pencil  of 
lines  is  a  series  of  lines  which  meet  in  a 
point. 

PE'NDULUM.  Every  solid  body  which 
is  freely  suspended,  is  called  a,  pendulum. 
A  distinction  is  made  between  the  simple 
or  mathematical,  and  the  compound  or 
physical  pendulum.  The  former  is  re- 
garded as  an  inflexible  imponderable 
line  suspended  at  one  end,  its  other  end 
being  considered  as  a  point  possessing 
weight.  A  pure  mathematical  pendulum 
has  no  actual  existence.  All  such  as 
actually  exist  are  physical  pendulums, 
every  material  particle  of  which  acts 
as  the  heavy  point  of  the  simple  pen- 
dulum. A  seconds  pendulum  is  one 
whose  vibration  occupies  one  second. 

PENI'NSULA  (pene,  nearly,  insula, 
an  island).  A  part  of  a  continent  which 
runs  out  into  the  sea,  and  is  joined  to 
the  main  land  by  only  a  small  portion  of 
its  circumference.  If  the  projections  of 
land  reach  but  a  little  way  into  the  sea, 
they  are  called  capes,  promontories,  or 
headlands. 

PENNATU'LID.E  {pennatula,  a  little 
feather).  A  family  of  cortical  polyps,  in 
which  the  whole  animal  resembles  a 
feather,  the  stem  supporting  lateral 
branches,  upon  which  the  polyps  are 
arranged. 

PENTA'CRINITE  (TreVre,  five,  npivov, 
a  lily).  A  pedunculated  star-fish  with 
five  rays,  for  the  most  part  fossil.  The 
animal  is  so  complicated  that  the  num- 
ber of  separate  pieces  of  stone  of  which 
its  singular  skeleton  is  made  up  has  been 
calculated  to  amount  to  not  fewer  than 
one  hundred  and  fifty  thousand. 

PE'NTAGON  {irevre,  five,  futvla,  an 
angle).  A  plane  geometrical  -  figure, 
bounded  by  five  sides,  and  consequently 
having  five  angles.  When  the  sides  and 
angles  are  all  equal,  the  pentagon  is 
called  regular,  and  then  the  square  of 
its  side  is  equal  to  the  sum  of  the  squares 
of  the  sides  of  the  hexagon  and  decagon 
inscribed  in  the  same  circle  as  the  pen- 
tagon. 

PENTA-GYNIA    (ti/vJj,    a   woman). 
Having   five    pistils ;    an    ordinal    cha- 
racter of  plants  in  the  system  of  Lin- 
naeus. 
PENTAKE'NIUM.    The  name  given 
252 


by  Richard  to  that  modification  of  the 
polakenium,  in  which  the  fruit,  so  desig- 
nated, has  five  akenia,  or  cells.  See 
Cremocarpium. 

PENTA'MERA  (r*rr«,  five,  fiepos,  a 
paf%).  A  section  of  Coleopterous  insects, 
in  Which  the  tarsi  of  all  the  feet  are  five- 
jointed,  the  fourth  being  of  ordinary  size. 
Latreille. 

PENTA'NDRIA  (Trevre,  five,  Uvrjp,  a 
man).  Having  five  stamens;  the  cha- 
racteristic feature  of  the  fifth  class  of 
plants  in  the  system  of  Linnaeus. 

PENU'MBRA  {pene,  almost,  umbra, 
a  shadow).  A  partial  shadow ;  an 
intermediate  shade  between  pure  sha- 
dow and  light;  a  shadow  which  re- 
ceives only  a  portion  of  the  rays  of 
a  luminous  body,  when  that  body  has 
a  measurable  diameter.  It  occurs  in 
solar  and  lunar  eclipses,  in  the  form  of 
two  diverging  spaces,  one  on  each  side  of 
the  cone  of  umbra,  or  pure  shadow, 
caused  by  the  interception  of  the  sun's 
rays.  In  a  solar  eclipse,  so  long  as  any 
part  of  the  sun  is  visible,  the  observer 
is  in  the  penumbra,  and  not  in  the 
umbra  or  complete  shadow. 

PEPERI'NO.  An  Italian  name  for  a 
particular  kind  of  volcanic  rock,  formed, 
like  tuff,  by  the  cementing  together  of 
volcanic  sand,  cinders,  scoriae,  &c. 

PEPO.  A  gourd ;  a  three-celled  fleshy 
indehiscent  fruit,  with  parietal  placentae, 
as  the  cucumber.  Richard  uses  the  term 
peponida. 

PE'PSIN  (TreTTTO),  to  digest).  A  pecu- 
liar animal  principle  secreted  by  the 
stomach  and  present  in  the  gastric  juice. 

PER.  A  Latin  preposition,  which, 
when  prefixed  to  the  name  of  an  oxide, 
indicates  the  presence  of  the  greatest 
quantity  of  oxygen  which  can  exist  in 
a  compound,  as  in  per-oxide. 

Bi-per.  This  double  prefix  is  used, 
when  there  is  more  than  one  atom  of 
oxygen  in  the  base,  as  well  as  an  unequal 
number  of  atoms  of  acid  and  base,  as  in 
the  ii^per-sulphate  of  mercury,  where 
bi  indicates  the  presence  of  two  atoms  of 
acid,  and  per  that  the  mercury  is  in  the 
form  of  a  per-oxide. 

PER  ACCIDENS.  A  term  formerly 
employed  in  philosophical  language  to 
denote  an  effect  which  does  not  follow 
from  the  nature  or  essence  of  the  thing, 
but  from  some  accidental  circumstance 
or  quality;  in  this  sense,  it  is  opposed 
to  the  term  per  se :  thus,  fire  burns  per 
se ;  a  red-hot  iron  burns  per  accidens. 
In  Logic,  the    term  per  accidens   is 


PER 


PER 


applied  to  that  mode  of  conversion  of  a 
proposition  in  which  the  quantity  is 
changed,  or  limited  from  universal  to 
particular.  This  might  fairly  be  named 
conversion  by  limitation,  but  is  com- 
monly called  conversion  per  accident. 

PERCE'PTION.  The  mental  faculty 
•by  which  we  hold  communication  with 
the  actual  world.  1.  It  is  thus  distin- 
guished from  conception,  which  relates  to 
that  which  has  no  reality :  we  perceive 
the  present  order  of  things,  we  conceive 
of  the  future.  Thus  the  ancients  dis- 
tinguished the  ai(rOt]Ta,  or  objects  of  per- 
ception, from  the  von™,  or  objects  of 
conception.  2.  Perception  differs  from 
consciousness,  in  the  subjects  of  the 
former  being  external,  those  of  the  latter 
internal :  we  perceive  a  mountain,  we  are 
conscious  of  a  thought.  3.  It  differs 
from  remembrance,  in  respect  to  the  sub- 
jects being  present  or  past :  we  remember 
a  former  object  of  perception,  but  we  do 
not  perceive  it  until  it  is  again  present. 
4.  But  the  term  u  perception  "  is  vaguely 
applied  by  some  writers  to  all  operations 
and  states  of  mind,  comprising  the  pas- 
sions, and  all  the  phenomena  of  memory 
and  of  imagination. 

PE'RCIDjE  (perca,  the  perch).  The 
Perch  tribe  ;  a  family  of  Acanthopterygi- 
ous,  or  spiny-finned  fishes.  In  the 
thoracic  species,  the  ventral  fins  are 
placed  under  the  pectoral ;  in  the  jugular, 
upon  the  throat ;  in  the  abdominal,  on 
the  abdomen. 

PERCU'SSION  (percutio,  to  strike). 
A  forcible  stroke  given  to  a  resisting  ob- 
ject by  a  moving  body.  There  is  one 
point  of  the  moving  body  in  which  the 
whole  force  of  the  stroke  is  concentrated, 
and  the  resistance  to  which  would  neu- 
tralize the  blow.  This  point  is  termed 
the  centre  of  percussion,  and  it  always 
coincides  with  that  of  oscillation  ;  and  if 
all  parts  of  the  percutient  body  be  carried 
forward  with  the  same  celerity  (which  is 
not  the  case  of  the  pendulum),  the  centre 
of  percussion  is  the  same  with  the  centre 
of  gravity.  The  force  of  percussion  is  mo- 
mentum.   See  Momentum. 

PERDICI'N,E  {perdix,  a  partridge)* 
Perdicine  birds,  or  partridges;  a  family 
of  the  i  Rasores,  or  Scratching  birds. 
There  is  little  essential  difference  be- 
tween the  large,  long-tailed  birds,  called 
Cocks  and  Pheasants,  and  the  small, 
short-tailed  species,  called  Partridges  and 
Quails.  Their  habits  also  are  essentially 
similar. 

PERE'NNIBRA'NCHIATE    (peren- 

253  w 


nis,  perpetual,  branchiae,  gills).  A  divi- 
sion of  Amphibious  animals,  which  pre- 
serve their  branchiae  through  the  whole 
period  of  their  lives,  as  the  proteus,  the 
siren,  &c. 

PERFECT  NUMBER.  A  number 
which  is  equal  to  the  sum  of  all  its  divi- 
sors. Thus  6  is  a  perfect  number,  for  its 
divisors  are  1,  2,  and  3,  and  the  sum  of 
these  is  6.     See  Number. 

PERFOLIATE.  The  designation  of 
a  leaf  which,  by  union  of  its  margins, 
encloses  the  stem,  which  thus  seems  to 
pass  through  it. 

PERFORATED  (perforo,  to  pierce 
through).  Bored,  or  pierced  through,  as 
by  an  awl;  a  term  applied  to  the  ear- 
shells. 

PERI-,  PER-  (Trep/).  A  Greek  prepo- 
sition, signifying  around,  about,  ex- 
pressing the  relation  of  circumference  to 
centre,  and  so  strictly  different  from  ufi<pi. 

1.  Peri-anth  (avOov,  a  flower).  A  collec- 
tive term  for  the  calyx  and  corolla  com- 
bined, the  limits  of  which  are  undefined, 
so  that  they  cannot  be  satisfactorily  dis- 
tinguished from  each  other,  as  in  tulip, 
orchis,  &c. 

2.  Peri-carp  (tcapiros,  fruit).  A  botani- 
cal term  denoting  all  the  parts  of  a  ripe 
fruit  which  are  on  the  outside  of  the  real 
integuments  of  the  seed,  except  the  aril. 
These  parts  are,  severally,  the  epicarp, 
the  sarcocarp,  and  the  endocarp. 

3.  Peri-cladium  (/cXa3or,  a  young 
branch).  A  term  sometimes  applied  to 
the  lower  part  of  a  petiole,  when  this 
part  sheaths  the  branch,  as  in  Apiaceae. 

4.  Peri-chcetium  (xaiTn,  seta,  a  hair). 
A  term  applied  to  the  peculiar  leaves 
which  surround  the  base  of  the  seta,  or 
stalk  of  the  sporangium,  or  seed-vessel 
of  mosses. 

5.  Peri-clinium  (nXivn,  a  couch).  The 
name  given  by  Cassini  to  the  involucrum 
of  composite  plants.  It  is  to  be  lamented 
that  botanists  cannot  agree  in  employing 
the  same  term  for  an  organ.  Besides  the 
above  designation  of  the  involucrum, 
Linnaeus  called  it  calyx  communis, 
Necker,  perigynandra  communis,  and 
Richard  periphoranthium. 

6.  Per-enchyma.  In  the  nomenclature 
of  vegetable  tissues  propounded  by 
Morren,  this  term  is  applied  to  the 
amylaceous  granules  contained  within 
the  tissue  of  plants. 

7.  Peri-gee  (-yfj,  the  earth).  That  point 
in  a  planet's  orbit  in  which  it  is  nearest 
to  the  earth.  Its  apogee  is  that  point  in 
which  it  is  furthest  from  the  earth. 


PER 


PER 


8.  Peri-gonium  {fovrj,  generation).  A 
term  synonymous  with  perianthium, 
and  denoting  the  parts  which  surround 
the  organs  of  generation  in  plants, 
viz.  the  floral  envelopes. 

9.  Peri-gynium  {^wrj,  a  woman).  A 
term  which  has  been  variously  employed 
by  botanical  writers.  Link  applied  it  to 
the  disk  found  in  certain  plants.  With 
some,  it  is  synonymous  with  urceolus ; 
with  others,  it  relates  to  the  hypogynous 
setce  found  at  the  base  of  the  ovary  of 
cyperaceae. 

10.  Peri-gynous  (71^,  a  woman).  That 
condition  of  the  stamens  of  a  plant  in 
which  they  contract  adhesion  to  the  sides 
of  the  calyx,  as  in  the  rose. 

11.  Peri-helion  (#\tor,  the  sun).  An 
astronomical  term,  denoting  the  greatest 
approximation  of  a  planet  to  the  sun.  See 
Aphelion. 

12.  Peri-meter  (/lerpov,  a  measure). 
The  bounding  line  of  any  plane  figure,  of 
whatever  parts  or  shapes  that  line  may 
consist.  The  bounding  line  of  a  circle,  or 
perhaps  of  any  curve  which  returns  upon 
itself,  is  termed  the  circumference  or 
periphery. 

13.  Peri-oeci  (oIkos,  a  habitation). 
Those  who  live  under  the  same  parallel 
of  latitude,  whether  north  or  south,  but 
on  opposite  meridians. 

14  Peri-ostracum  {ocrpaKov,  a  shell). 
The  epidermis,  or  membrane  analogous 
to  scarf-skin,  which  covers  shell. 

15.  Peri-phery  (cpepoo,  to  carry).  The 
line  which  bounds  a  circular  body;  a 
circumference,  as  that  of  a  circle,  an 
ellipse,  or  any  other  curvilinear  figure. 

16.  Peri-phyllia  (<pv\\ov,  a  leaf.)  The 
term  applied  by  Link  to  the  minute 
hypogynous  scales  found  within  the 
paleae  of  grasses.  These  little  organs 
have  disturbed  the  nomenclature  of 
botany  not  a  little ;  for  while  some  call 
them  corolla,  others  call  them  squamulce, 
Linnaeus  nectarium,  Richard  glumella, 
De  Candolle  glumellula,  and  De  Beauvois 
lodicula. 

17.  Peri-scii  (aula,  shadow).  The  inha- 
bitants of  the  polar  circles ;  those  whose 
shadows  make  complete  revolutions,  in 
consequence  of  the  sun  being  present  for 
twenty-four  hours  together.  See  Hete- 
roscii. 

18.  Peri-sperm  {anepua,  a  seed).  An- 
other name  for  the  albumen,  or  the  sub- 
stance lying  between  the  integuments 
and  the  embryo  of  the  seed.  By  Richard, 
the  term  is  applied  to  the  testa  or  sper- 
moderm  of  other  writers. 

254 


19.  Peri-sporum  (anopos,  a  seed,  a 
spore).  The  name  given  by  some  French 
writers  to  the  hypogynous  setce  found  at 
the  base  of  the  ovary  of  Cyperaceae.  They 
have  also  been  termed  perigynium. 

20.  Peri-stomians  {aro/xa,  the  mouth). 
The  name  given  by  Lamarck  to  a  family 
of  Gasteropods,  consisting  of  the  genera 
Valvata,  Paludina,  and  Ampullaria. 
Cuvier  comprises  these  under  his  tro- 
choid pectinibranchians. 

21.  Peri-stomium  (arofxa,  the  mouth). 
The  membrane,  or  series  of  tooth-like 
processes,  which  closes  the  orifice  of  the 
theca  of  mosses.  Strictly  speaking,  it 
consists  of  two  membranes,  and  hence 
we  hear  of  an  inner  and  an  outer 
peristomium.  The  organ  is  highly  hy- 
grometrical. 

22.  Peri-thecium  (9t]Kn,  a  theca,  or 
case).  The  case  which  contains  the  re- 
productive organs  of  certain  fungi.  Peri- 
dium  is  also  a  kind  of  covering  of  spori- 
dia ;  peridiolum  is  its  diminutive. 

23.  Peri-trema  (xpfj^a,  a  hole).  The 
raised  margin  which  surrounds  the 
breathing  holes  of  scorpions. 

24.  Peri-tropal  {rpeirui,  to  turn).  A 
botanical  term  applied  to  the  embryo  of 
the  seed,  when  it  is  directed  from  the 
axis  to  the  horizon. 

PE'RICLINE.  A  felspathic  substance, 
united  by  some  mineralogists  with  ice- 
spar,  and  found  in  the  Tyrol,  St.  Go- 
thard,  &c. 

PERI  DOTE.  Chrysolite.  A  silicate 
of  magnesia,  constituting  olivine  in  its 
purer  state. 

PERIOD.  The  time  occupied  by  a 
planet  in  making  a  revolution  round  the 
sun ;  or  the  duration  of  its  course  till  it 
returns  to  the  same  point  of  its  orbit. 
In  Arithmetic,  a  period  is  the  recurring 
part  of  a  circulating  decimal.  For  its 
chronological  meaning,  see  Cycle. 

PERIO'DIC  ACID.  An  acid  consist- 
ing of  iodine  and  oxygen. 

PERIO'DIC  FUNCTIONS.  Trigono- 
metry has  for  its  subject  periodic  magni- 
tude, i.  e.  magnitude  which  varies  in 
such  a  manner  as  to  go  through  stated 
cycles  of  changes,  each  cycle  being  a 
reiteration  of  the  preceding  one.  Peri- 
odic functions  are  those  which,  performed 
any  given  number  of  times  on  a  variable, 
reproduce  the  simple  variable  itself. 
Thus  1 — x  and  — x  are  periodic  func- 
tions of  the  second  order,  since 

1—  (1—  x)  =  x,         — (— -x)=x. 

PERIODICAL  STARS.  Stars  which 
undergo  a  regular  periodical   increase 


PER 


PET 


and  diminution  of  lustre,  involving  in 
one  or  two  cases  a  complete  extinction 
and  revival.  One  of  the  most  remark- 
able of  these  is  the  star  Omicron,  in  the 
southern  constellation  Cetus,  first  noticed 
by  Fabricius  in  1596. 

PERIODICAL  WINDS.  Winds  which 
blow  half  the  year  in  one  direction,  and 
half  the  year  in  the  opposite  direction. 
October  and  April  are  the  two  months,  in 
which  the  change  in  the  direction  of 
these  winds  usually  takes  place.  See 
Monsoon. 

PERKINS'S  STEAM-ENGINE.  A 
modification  of  the  steam-engine,  in 
which  there  is  no  proper  boiler,  but  the 
water  is  heated  to  a  high  temperature  in 
a  cylindrical  vessel,  called  a  generator, 
thence  discharged  through  a  valve,  and 
immediately  converted  into  steam,  hav- 
ing a  pressure  equal  to  that  of  about  35 
atmospheres,  or  of  about  500  lbs.  on  the 
square  inch ;  the  steam  at  this  high 
pressure  is  then  admitted  into  a  cylinder 
only  18  inches  long  and  2  inches  wide, 
the  piston  of  which  would  perform  200 
strokes  per  minute,  and  exert  a  force 
equal  to  10  horse  power. 

PERLATE  ACID.  The  name  given 
by  Bergman  to  the  acidulous  phosphate 
of  soda ;  the  phosphate  of  soda  had  been 
previously  called  sal  mirabile  perlatum. 
It  was  named  by  Guyton-Morveau, 
ouretic  acid. 

PERMANENT  INK.  A  solution  of 
nitrate  of  silver,  thickened  with  sap 
green  or  cochineal. 

PERMANENT  WHITE.  Sulphate  of 
baryta.  At  a  high  temperature  it  fuses 
into  an  opaque  white  enamel,  which  is 
used  in  the  manufacture  of  fine  earthen- 
ware, and  as  a  pigment. 

PERMEABILITY  (per,  through,  meo, 
to  pass).  That  property  of  certain  bodies 
by  which  they  admit  the  passage  of  other 
bodies  through  their  substance.  The 
cellular  tissue  of  plants  is  permeable  by 
fluids,  though  at  the  same  time  imper- 
forate. 

PERMIAN  SYSTEM.  Zechstein. 
Magnesian  Limestone  Formation.  Under 
these  names  is  designated  a  series  of 
•well-known  deposits  which  succeed  the 
carboniferous  rocks,  and  sometimes  pass 
into  them  by  insensible  gradations. 

PERMUTATIONS.  By  this  term  is 
meant  the  number  of  changes  which  any 
quantities,  a,  b,  c,  d,  &c,  may  undergo 
with  respect  to  their  order,  when  taken 
two  and  two  together,  three  and  three, 
&c.  &c.  The  number  of  changes  which 
255 


may    be   rung    upon     twelve    bells    is 
479,001,600.     See  Combinations. 

PE'RONATE  (pero,  a  sort  of  high 
shoe).  A  term  applied  in  botany  to  the 
stipes  of  fungaceous  plants,  which  is 
thickly  laid  over  with  a  woolly  substance, 
ending  in  a  sort  of  meal. 

PEROXIDE.  A  term  applied  in  che- 
mical nomenclature  to  denote  the  highest 
degree  of  oxidation,  of  which  a  compound 
is  capable.     See  Per. 

PERPENDICULAR.  A  term  applied 
in  geometry  to  that  straight  line  which, 
falling  upon  another  straight  line,  makes 
the  adjacent  angles  equal  to  each  other. 
Each  of  these  angles  will  be  a  right 
angle. 

PERSEUS.  A  northern  constellation 
consisting  of  fifty-nine  stars,  the  prin- 
cipal of  which  is  Algenib. 

PERSISTENT.  A  term  applied  to 
those  parts  of  plants  which  do  not  fall  at 
the  usual  period,  as  the  corolla  of  cam- 
panula, the  calyx  of  paeonia.  See  Cadu- 
cous. 

PERSONATE  (persona,  a  mask).  A 
term  applied  to  that  form  of  the  gamo- 
petalous  corolla,  in  which  the  limb  is 
unequally  divided :  the  upper  division, 
or  lip,  being  arched ;  the  lower  prominent, 
and  pressed  against  it,  so  that  the  whole 
resembles  the  mouth  of  a  gaping  animal, 
as  in  antirrhinum.     See  Ringent. 

PERSONIFICATION.  A  metaphor- 
ical mode  of  speech  by  which  inanimate 
objects  or  abstract  ideas  are  repre- 
sented as  possessed  of  life  and  action. 
Every  scholar  has  enjoyed  Virgil's  famous 
personification  of  the  grafted  tree  : — 
"  Miraturque  uovas  frondes,  et  non  sua  poma." 

PERSPECTIVE.  The  application  of 
geometrical  rules  to  the  delineation  of 
objects  on  a  plane  surface,  as  connected 
with  the  arts  of  design. 

PERTURBATIONS  (perturbo,  to  dis- 
turb). A  name  applied  to  those  inequa- 
lities in  the  lunar  and  planetary  motions, 
which  arise  from  the  universality  of  at- 
traction. Thus,  not  only  does  the  sun 
attract  the  earth,  and  the  earth  the  moon, 
but  these  attractions  are  all  reciprocal ; 
and  not  only  is  this  the  case,  but  each 
individual  planet  attracts,  and  is  attracted 
by,  all  the  rest. 

PETAL  (nera'Kov,  a  leaf).  In  Botany, 
a  flower-leaf;  one  of  the  divisions  of  a 
corolla.  In  some  plants,  as  in  nymphaea, 
the  filament  is  expanded,  and  resembles 
a  petal,  and  is  then  called  petaloid. 

PE'TALITE.  A  felspathic  substance, 
in  which  lithia  was  first  discovered  by 


PH  A 


PH  A 


Arfvedson.    It  is  a  silicate  of  lithia  and 
alumina. 

PETIOLE.  The  leaf- stalk  of  a  plant, 
or  that  which  connects  the  blade  with 
the  stem.  A  leaf  so  provided  is  called 
petiolate ;  if  otherwise,  sessile.  "When  a 
petiole  is  divided  into  several  parts,  each 
part  bearing  a  separate  leaf  or  leaflet,  it 
is  said  to  be  compound,  the  stalks  of  the 
leaflets  being  called  petiolules  or  stalk- 
lets. 

PETITIO  PRINCIPII.  A  non-logical 
or  material  fallacy  in  reasoning,  com- 
monly called  begging  the  question.  It 
takes  place  when  a  premiss,  whether 
true  or  false,  is  either  plainly  equivalent 
to  the  conclusion,  or  depends  on  it  for 
its  own  reception,  as  if  any  one  should 
infer  the  actual  occurrence  of  the  eclipses 
recorded  in  the  Chinese  annals,  from  an 
assumption  of  the  authenticity  of  those 
annals.     Whately. 

PETRIFACTIONS.  Stony  matters 
deposited  either  in  the  way  of  incrusta- 
tions, or  within  the  cavities  of  organized 
substances.  In  the  former  case,  carbo- 
nate of  lime  flows  over  wood  and  other 
organic  and  destructible  matters,  of 
which  it  preserves  the  form. 

PETROLE'UM  (irtrpa,  a  rock,  ZXauov, 
oil).  Rock  oil,  an  inflammable  liquid 
bituminous  substance,  differing  from 
naphtha  only  in  being  more  inspissated. 
It  receives  its  name  from  its  oozing,  like 
oil,  from  the  rock.  It  abounds  in  the 
United  States,  where  it  is  known  under 
the  name  of  Seneca  or  Genessee  oil. 

PETRO'SILEX.  A  name  probably 
given  to  two  different  minerals,  viz.  com- 
pact quartz  and  compact  felspar;  the 
latter  has  also  been  termed  fusible  petro- 
silex. 

PETUNTSE'.  A  species  of  felspar, 
constituting  the  vitrifying  ingredient  in 
Chinese  porcelain. 

PETWORTH  MARBLE.  Sussex 
Marble.  A  variously  coloured  limestone, 
occurring  in  the  weald  clay,  and  com- 
posed of  the  remains  of  fresh-water 
shells. 

PEWTER.  A  compound  metal  formed 
of  tin  and  lead,  in  the  proportions  of  80 
parts  of  the  former  to  20  of  the  latter. 

PHjENO'GAMOUS  {(paiva>,  to  show, 
ydyuof,  nuptials).  A  term  applied  to 
those  plants  in  which  the  reproductive 
organs  are  visible,  as  distinguished  from 
the  cryptogamous,  in  which  they  are  con- 
cealed, or  of  which  the  function  is  not 
understood.  The  term  is  synonymous 
with  phanerogamous. 
256 


PHENOMENA  {<palvoncu,  to  ap- 
pear). The  appearances  upon  which  a 
system  or  hypothesis  is  founded.  Thus 
the  apparent  motions  of  the  celestial 
bodies  are  phaenomena,  which  have  sug- 
gested the  systems  of  astronomers.  A 
hypothesis,  on  the  contrary,  is  an  assumed 
cause,  by  which  we  endeavour  to  explain 
a  particular  class  of  phaenomena. 

PHANEROGAMOUS  (0ai/eP6c,  evi- 
dent, fdfxot,  nuptials).  Phcenogamous. 
A  term  applied  by  botanists  to  those 
plants  in  which  the  organs  of  reproduction 
are  easily  distinguished.  They  comprise 
the  exogens  and  endogens  of  the  natural 
arrangement.     See  Cryptogamous. 

PHA'RMACOLITE.  Arsenic  bloom. 
Native  arseniate  of  lime,  occurring  in 
white  acicular  crystals,  in  veins  together 
with  tin-white  cobalt  at  Andreasberg,  &c. 

PHA'RMACOSIDE'RITE.  Arseniate 
of  iron,  occurring  crystallized,  chiefly  in 
cubes,  and  hence  called  by  Werner  cube- 
ore. 

PHARYNGI'N^  LABYRINTHI- 
FO'RMjE.  A  family  of  Acanthopterygi- 
ous  fishes,  in  which  the  membranes  of 
the  pharynx  are  divided  into  small  irre- 
gular leaves,  containing  cells,  which  the 
fish  can  at  pleasure  fill  with  water ;  and, 
by  ejecting  a  portion  of  this  water,  it 
moistens  its  gills,  and  is  thus  enabled  to 
continue  its  respiration  out  of  its  proper 
element. 

PHASES  (0d<m,  an  appearance).  A 
term  applied  in  astronomy  to  the  monthly 
changes  of  appearance  of  the  moon. 
When  she  appears  with  a  full  orb,  or 
with  all  her  surface  enlightened,  we  say 
the  moon  is  full.  When  a  part  only  of 
her  enlightened  hemisphere  is  towards 
the  earth,  and  that  part  is  convex,  the 
moon  is  said  to  be  gibbous  (gibbus, 
bunched  out).  When  a  half  only  of  her 
enlightened  hemisphere  is  visible  to  the 
earth,  we  speak  of  a  half-moon.  When 
a  very  small  portion  of  the  enlightened 
hemisphere  is  towards  us,  and  that  con- 
cave, the  moon  is  said  to  be  horned. 
Lastly,  when  none  of  her  enlightened 
hemisphere  is  towards  us,  we  say  the 
moon  changes,  or  it  is  new  moon. 

When  the  moon  is  full,  she  is  said  to 
be  in  opposition  to  the  sun  ;  when  new, 
she  is  said  to  be  in  conjunction :  these 
two  positions  are  called  syzygies.  In  the 
first  and  the  last  quarter,  half  her  illu- 
minated portion  is  visible;  these  posi- 
tions are  called  quadratures,  and  the  in- 
termediate points  between  them  and  the 
syzygies  are  called  octants. 


PIIL 


PHO 


PHA'SIANE'LLIN^E.  Pheasant  snails, 
a  sub-family  of  the  Trochidce,  or  Top 
Shells,  named  from  the  genus  phasi- 
anella,  in  which  the  shell  is  spiral  and 
obovate,  the  outside  polished,  and  the 
operculum  shelly. 

PHASIANI'DjE.  The  Pheasant  and 
Fowl  tribe  of  the  Rasores,  or  Scratching 
Birds,  distinguished  by  the  shortness  of 
the  hind  toe,  the  presence  of  spurs  on 
the  legs,  and  the  beautiful  development 
of  the  tail.  They  pass  gradually  into  the 
Perdicince,  there  being  no  real  distinction 
between  them. 

PHI'LLIPSITE.  A  zeolitic  substance 
belonging  to  that  division  of  the  har- 
motome  minerals,  which  contain  potass, 
as  distinguished  from  the  baryte-har- 
motome  species. 

PHILO'LOGY  (0iXo\o<y/a).  This  term, 
in  its  strict  etymological  sense,  denotes 
a  love  of  talking ;  generally,  it  signifies 
a  love  of  literature ;  in  modern  times  it 
has  been  restricted  to  the  study  of  lan- 
guage and  history. 

PHILOSOPHICAL  CANDLE.  A  bot- 
tle fitted  with  a  cork,  through  which  a 
slender  glass  or  metallic  tube  passes.  On 
introducing  the  materials  for  generating 
hydrogen,  and  fixing  the  cork  and  tube 
air-tight,  a  jet  of  hydrogen  is  discharged, 
which  may  be  ignited  by  the  application 
of  a  burning  body  or  an  electric  spark. 

PHILOSOPHY  (<t>i\o<ro<pia).  This 
term  denotes,  simply,  a  love  of  know- 
ledge. But  all  subjects  of  systematic 
inquiry,  ranging  from  that  of  the  opera- 
tions of  the  mind  to  those  of  the  arts 
and  manufactures,  have  their  philoso- 
phies ;  and  hence,  although  the  term 
carries  with  it  no  great  precision,  its  ap- 
plication in  any  particular  case  is  suffi- 
ciently obvious. 

PHLEGRjE'AN  FIELDS  (<p\ey<a,  to 
burn).  Campi  Phlegrcei,  or  the  "Burnt 
Fields."  The  country  round  Naples,  so 
named  by  the  Greeks,  from  the  traces 
of  igneous  action  every  where  visible. 

PHLG2UM  ((pXotos,  bark).  Peridermis. 
The  name  given  by  Mohl  to  one  of  the 
layers  of  bark,  the  epi-phlceum  of  Link. 
See  Bark,of  Plants. 

PHLOGISTON  ((p*eya>,  to  burn).  A 
name  given  by  Stahl  to  an  imaginary 
substance,  which  was  the  principle  of  in- 
flammability. Combustible  bodies  were 
supposed  to  consist  of  an  incombustible 
base,  united  to  this  phlogiston,  which 
escaped  during  combustion.  This  pro- 
cess is  now  attributed  to  the  combination 
of  combustible  matter  with  oxygen, 
257 


which  is  hence  called  a  supporter  of  com- 
bustion. 

PHLORIDZIN  (tf>Xot6p,  bark).  A 
substance  discovered  in  the  bark  of  the 
root  of  the  apple,  pear,  cherry,  and  plum- 
tree.  It  has  been  considered  as  crystal- 
lized salicin  plus  two  atoms  of  oxygen. 

PHOCENIC  ACID  (phoccena,  a  por- 
poise). Delphinic  acid.  A  volatile  acid 
contained  in  train  oil  or  seal  oil,  and  in 
the  berries  of  Viburnum  opulus. 

PHO'CIDjE  (phoca,  a  seal).  The 
Seal  tribe  of  carnivorous  Vertebrata,  the 
Amphibia  of  Cuvier,  distinguished  by 
the  adaptation  of  their  form  and  struc- 
ture to  a  residence  in  the  water,  and  of 
their  teeth  for  retaining  a  hold  on  the 
slippery  surface  of  fish,  and  crushing 
them  before  they  are  swallowed. 

PHCENICIN  {<t>oivi$,  purple).  Indigo- 
purple  ;  supposed  to  be  a  hydrate  of  in- 
digo, with  two  equivalents  of  water. 

PHC2NIX.  A  modern  southern  con- 
stellation, consisting  of  thirteen  stars. 

PHO'LARITE.  Hydrated  silicate  of 
alumina ;  a  substance  occurring  in  small 
pearly  scales  in  the  coal  formation  of 
Fins. 

PHO'LIDjE.  A  family  of  macrotra- 
chian  bivalves,  named  from  the  genus 
pholas ;  in  these  the  valves  are  often 
prolonged  in  a  shelly  tube,  resembling 
that  of  the  Tubulibranchiata. 

PHONETIC  WRITING  (fuvij, 
sound).  A  kind  of  hieroglyphic  writing 
employed  by  the  ancient  Egyptians,  in 
which  the  characters  represent,  not 
objects,  but  sounds.  The  figures  repre- 
senting letters  were  the  likenesses  of 
certain  animals  or  other  objects,  the 
names  of  which  began  with  those  letters. 
The  phonetic  was  thus  opposed  to  the 
ideographic  writing,  in  which  the  charac- 
ters represented  objects,  or  symbolically 
denoted  abstract  ideas.  See  Hiero- 
glyphics. 

PHO'NICS  {<p(avtj,  sound).  A  term 
synonymous  with  acoustics,  denoting  the 
doctrine  of  sound.  The  phenomena  of 
direct,  reflected,  and  refracted  sound 
have  given  rise  to  the  three  respectively 
corresponding  terms  of  phonics,  cata- 
phonics,  and  diaphonics. 

PHONOLITE  (0a>i/»/,  sound,  \i$ov,  a 
stone).  Clinkstone.  A  felspathic  rock  of 
the  trap  family,  usually  fissile,  and 
named  from  its  sonorous  property,  when 
struck  with  a  hammer. 

PHORA'NTHIUM  (0«?Po>,  to  bear, 
avOot,  a  flower).  The  term  applied  by 
Richard  to  the  receptacle  of  composite 


PHO 


PHO 


plants.  This  is  the  thalamus  and  cli- 
nanthium  of  other  writers. 

PHOSGENE  GAS  {<pS>s,  light,  yewdco, 
to  produce).  Chloro-carbonic  acid  gas; 
a  compound  of  chlorine  and  protoxide  of 
charcoal.  It  is  named  from  the  peculiar 
power  of  the  sunbeam  in  effecting  this 
combination. 

PHOSPHATE.  A  salt  formed  by  the 
union  of  phosphoric  acid  with  a  sala- 
fiable  base. 

PHO'SPHITE.  A  salt  formed  by 
the  union  of   phosphorous  acid  with  a 

PHOSPHORESCENCE  (tf>wp,  light, 
<pepa>,  to  carry).  The  emission  of  light 
by  many  bodies  at  a  low  temperature, 
unaccompanied  by  any  essential  change 
in  their  properties.  The  luminous  ap- 
pearance of  common  phosphorus  is  the 
result  of  chemical  action,  for  it  takes 
place  only  when  this  substance  is  in 
combination  with  oxygen  or  chlorine. 

1.  Phosphorescence  by  insulation  is  a 
property  possessed  by  many  bodies,  in 
consequence  of  which,  after  long  ex- 
posure to  the  sun's  rays,  they  become 
luminous  in  the  dark  on  the  application 
of  heat.  Of  this  kind  are  the  phosphorus 
of  Baldwin,  or  the  ignited  muriate  of 
lime  ;  phosphorus  of  Canton,  consisting 
of  oyster-shells,  calcined  with  sulphur; 
and  the  Bologna  stone,  or  the  sulphate  of 
barytes. 

2.  Phosphorescence  of  organic  remains 
in  a  state  of  dissolution.  This  luminous 
property  occurs  in  touchwood,  and  in 
sea-fish,  on  which  a  luminous  film  is 
formed.  The  phosphorescence  appears 
to  be  owing  to  a  low  sort  of  combustion, 
as  the  emission  of  light  decreases  on 
rarefying  the  air. 

3.  Phosphorescence  of  organic  bodies 
during  life.  This  occurs  in  the  marigold 
and  yellow  lily,  a  little  after  sunset,  when 
the  atmosphere  has  been  very  much 
heated  in  July  and  August.  It  is  pro- 
bably of  an  electrical  nature.  The  lu- 
minosity of  the  infusoria,  zoophytes, 
fire-flies,  and  glow-worms,  is  a  subject  of 
much  obscurity. 

PHO'SPHORITE.  A  sub-species  of 
apatite,  comprising  the  fibrous  and  the 
compact  phosphates  of  lime. 

PHO'SPHORUS  (<pw,  light,  0<?po>,  to 
carry).  A  solid,  semi-transparent  colour- 
less substance,  of  a  waxy  consistence, 
undergoing  slow  combustion  at  ordinary 
temperatures  ;  burning  brilliantly  in  air. 
Combined  with  lime,  it  is  a  principal 
constituent  of  the  bones  of  vertebrated 
258 


animals,  and  is  found  in  some  kinds  of 
limestone. 

1.  Phosphorous  acid.  An  acid  pro- 
duced, in  the  form  of  a  white  volatile 
powder,  by  the  slow  combustion  of 
phosphorus.  Its  salts  are  called  phos- 
phites. 

2.  Phosphoric  acid.  An  acid  obtained, 
in  the  form  of  white  flakes,  by  igniting 
phosphorus  under  a  large  bell  jar.  Its 
salts  are  called  phosphates. 

PHO'SPHURET.  A  compound  of 
phosphorus  with  a  combustible  or  a 
metallic  oxide. 

PHOSPHY'TTRITE.  Phosphate  of 
yttria ;  a  very  scarce  mineral  substance, 
first  found  in  the  granite  of  Lindenas  in 
Norway,  and  subsequently  in  equally 
small  quantities  at  Ytterby  in  Sweden. 

PHO'TICITE.  A  mixture  of  the  sili- 
cate and  the  carbo-silicate  of  manganese. 

PHOTOGE'NIC  DRAWING  {<pZt, 
0o)Tor,  light,  fewdu),  to  produce).  A 
modern  discovery  by  which  objects  are 
represented  by  the  chemical  action  of 
light  on  a  prepared  metallic  tablet,  upon 
which  the  images  of  the  objects  are 
thrown  by  a  camera  obscura.  The  dis- 
covery was  made  by  Daguerre ;  and  the 
apparatus  was  hence  called  Daguerreo- 
type ;  and  the  process  itself  photogeny, 
photography,  or  heliography. 

PHOTO'GRAPHY  (0Sr,  <P<ot6v,  light, 
•ypa^a),  to  delineate).  Heliography.  The 
application  of  the  chemical  effects  of 
light  to  the  purpose  of  rendering  perma- 
nent the  images  obtained  by  means  of 
convex  lenses.     See  Daguerreotype. 

PHOTO'METER  (0Sf,  ^w-rof,  light, 
fxerpov,  a  measure).  An  instrument  for 
measuring  the  relative  illuminating 
powers  of  different  sources  of  light.  In 
Rumford's  photometer,  the  depth  of  the 
shadow  is  the  measure  used  for  com- 
paring the  intensities  of  different  lights ; 
in  Ritchie's,  the  brightness  of  the  illu- 
mination answers  the  same  purpose. 
When  the  shadows  are  equally  deep,  or 
when  the  illuminations  are  equally 
bright,  the  luminous  powers  of  the  two 
sources  of  light  will  be  as  the  squares  of 
the  distances  at  which  they  act. 

Leslie's  Photometer  consists  of  the 
differential  thermometer  with  one  of  the 
balls  blackened.  The  clear  ball  transmits 
all  the  light  that  falls  upon  it,  and  there- 
fore its  temperature  is  not  affected  ;  the 
black  ball,  on  the  contrary,  absorbs  all 
the  light,  and  a  corresponding  elevation 
of  temperature  takes  place.  The  action  of 
the  photometer  depends,  therefore,  on 


PHY 


PHY 


the  heat  produced  by  the  absorption  of 
light. 

PHRA'GMOCONE  (<pPayp.a,  a  parti- 
tion, kwvos,  a  cone).  The  chambered 
cone  of  the  shell  of  the  Belemnite. 

PHRASE  (in  Music).  This  term  is 
denned  by  Rousseau  as  a  succession  of 
sounds  in  melody  or  harmony,  expressing 
an  unbroken  sense  more  or  less  complete, 
and  terminating  in  a  pause,  thus  forming 
a  cadence  more  or  less  perfect.  But  the 
notions  entertained  of  this  term  are 
various. 

PHRENO'LOGY  (*>**  the  mind, 
Aoyos,  an  account).  The  name  of  a 
science  introduced  by  Gall  and  Spurz- 
heim,  by  which  particular  characters  and 
propensities  are  indicated  by  the  con- 
formation and  protuberances  of  the  skull. 

PHYCOMA'TER  (ipvuos,  sea-weed, 
liijTnp,  mother).  The  name  given  by 
Fries  to  the  gelatine  in  which  the  sporules 
of  byssaceous  plants  first  vegetate. 

PHYLLI'DIANS.  The  name  given 
by  Lamarck  to  a  family  of  Gasteropodous 
molluscs,  typified  by  the  genus  phyllidia, 
and  characterized  by  the  position  of  the 
branchia  in  a  circle  round  the  body  be- 
tween the  foot  and  the  mantle. 

PHYLLO'DIUM  {<pv\\ov,  a  leaf).  A 
term  applied  to  the  petiole  of  a  leaf, 
when  it  is  expanded  and  leafy,  and  the 
lamina  abortive,  as  in  many  species  of 

PHYLLONY'CTERANS  (<pv\\ov,  a 
leaf,  vvKTepJf ,  a  bat).  A  primary  division 
of  the  Cheiroptera,  commonly  termed  the 
"foliated  bats,"  from  the  peculiar  mem- 
branous foliations  which  in  these  animals 
serve  the  purpose  of  antennae. 

PHYLLO'PODA  (<pv\Xov,  a  leaf,  noi>t , 
jrodof,  a  foot).  An  order  of  the  bran- 
chiopodous  Crustacea,  in  which  the  body 
is  elongated,  and  the  extremities  flattened 
for  the  purpose  of  swimming,  as  in  the 
branchipus. 

PHYLLOSO'MA  {<pv\\ov,  a  leaf,  o-w/ia, 
the  body).  The  family  of  double-cuirassed 
crustaceans,  the  forms  of  which  are  re- 
markable for  their  rounded  shape  and 
the  transparency  of  their  integuments. 

PHYLLOSTOMI'NjE  (<p6\\ov,  a  leaf, 
o-To/ua,  the  mouth).  A  family  of  insec- 
tivorous Cheiroptera,  which  have  the 
nasal  appendage  simple  and  fleshy,  and 
to  which  the  celebrated  vampyre  belongs. 

PHY'SALITE.  Pyrophysalite.  A  sub- 
species of  prismatic  topaz,  found  in 
granite  at  Finbo  in  Sweden. 

PHYSCOSTE'MON  (</>ucrcza>,  to  swell, 
crfjuav,  a  stamen).  The  name  given  by 
259 


Turpin  to  a  fleshy  body  found  in  certain 
plants  between  the  base  of  the  stamens 
and  the  base  of  the  ovary.  It  is  com- 
monly called  the  disk. 

PHYSICAL  DEFINITION.  A  defi- 
nition which  assigns  the  parts  into 
which  the  thing  defined  can  be  actually 
divided.  Thus,  a  plant  would  be  defined 
physically,  by  enumerating  the  root, 
stalk,  leaves,  &c,  of  which  it  is  com- 
posed. Logically,  it  would  be  defined 
"  an  organized  being,  destitute  of  sensa- 
tion," the  former  of  these  expressions  de- 
noting the  genus,  the  latter  the  difference. 

PHY'SICS  {(pvarti,  nature).  That  de- 
partment of  science  which  treats  of  the 
properties  of  bodies,  the  laws  of  motion, 
and  the  general  phenomena  of  nature. 
It  is  commonly  termed  Natural  Philoso- 
phy and  Mechanical  Philosophy.  Bacon 
endeavours  to  draw  a  line  between  phy- 
sics and  metaphysics ;— "  Physic  is  that 
which  inquires  of  the  efficient  cause  and 
of  the  matter ;  metaphysic,  that  which 
inquires  of  the  form  and  end." 

PHYSIO'GNOMY  {<pv<rioyva>p.ovia). 
The  science  or  art  of  judging  of  a  per- 
son's character  by  his  outward  look. 

PHYSIOLOGY  {<p6<ris,  nature,  \d70r, 
an  account).  The  science  which  treats 
of  the  properties  of  organic  bodies,  ani- 
mal and  vegetable ;  of  the  phenomena 
which  they  present ;  and  of  the  laws 
which  govern  their  actions. 

PHYSO'GRADA.  An  order  of  the 
Acalephce,  in  which  the  body  is  supported 
in  the  water  by  means  of  one  or  more 
bladders,  capable  of  being  filled  with  air 
at  the  will  of  the  animal,  and  which, 
when  partially  empty,  enable  the  animal 
to  sink  on  the  approach  of  danger.  These 
are  the  hydrostatic  acalephce  of  Cuvier. 
M.  de  Blainville  considers  the  Physo- 
grada  as  one  of  the  aberrant  or  false 
forms  of  the  Zoophytes,  and  as  animals 
improperly  referred  to  them. 

PHYTO'GRAPHY  (<pvrbv,  a  plant, 
7pa0o),  to  write).  An  account  of  the 
rules  observed  in  describing  and  naming 
plants. 

PHYTO'LOGY  (<pVrov,  a  plant,  Aoyor, 
an  account).  That  branch  of  science 
which  treats  of  the  forms  and  properties 
of  plants. 

PHYTOTHAGOUS  (<pvr6v,  a  plant, 
(pdya,  to  eat).  Plant-eating ;  a  term  ap- 
plied to  a  division  of  cetaceous  animals, 
and  to  a  tribe  of  plant-eating  gasteropods. 
See  Zoophagous. 

PHYTO'TOMY  (<f>vc6v,  a  plant,  refxvto, 
to  cut).    Vegetable  anatomy ;  the  display 


PIL 


PIN 


of  the  tissues  of  plants  by  means  of  dis- 
section. 

PHYTOZO'A  (<puTov,  a  plant,  £wov,  an 
animal).  Animal  plants,  or  polyps ;  a 
class  of  Radiate  animals,  named  from 
their  plant-like  forms  ;  the  Zoophytes  of 
old  authors. 

PHYTOZOA'RIA  {<j>vr6v,  a  plant, 
£5oi/,  an  animal).  A  term  applied  by 
Ehrenberg  to  those  minute  aquatic  ani- 
mals which  are  more  commonly  termed 
infusoria  and  microzoaria.  They  are 
distinguished  into  the  polygastrica  and 
the  rotifera. 

PI'CAMAR  (in  pice  amarum).  The 
bitter  principle  of  tar,  and  of  all  empy- 
reumatic  products. 

PI'CIDiE  (picus,  a  woodpecker).  Picine 
birds,  or  woodpeckers;  a  family  of  the 
Scansores,  or  Climbing  birds,  character- 
ized by  their  long,  straight,  angular 
beak,  the  end  of  which  is  compressed 
into  a  wedge,  adapted  to  perforate  the 
bark  of  trees. 

PICRO'LITE.  A  green  or  yellow 
mineral  consisting  chiefly  of  magnesia ; 
found  traversing  beds  of  magnetic  iron 
ore. 

PICRO'SMINE  (mnpos,  bitter,  baixrj, 
odour).  A  mineral  species,  consisting  of 
silicate  of  magnesia;  found  in  the  iron 
mine  of  Englesburg,  in  Bohemia. 

PICROTO'XIN.  The  deleterious  prin- 
ciple of  the  cocculus  indicus.  It  is  ex- 
tracted by  means  of  water  and  alcohol, 
and  eventually  crystallizes. 

PIERRE  DE  TRIPES.  The  name 
given  to  a  sub  species  of  prismatic  gyp- 
sum, or  anhydrite,  from  its  convoluted 
concretions. 

PIEZO'METER  (™£a>,  to  press, 
nerpov,  a  measure).  An  instrument  for 
ascertaining  the  compressibility  of 
liquids. 

PILE.  An  apparatus  for  exhibiting 
the  phenomena  of  Galvanism,  and  con- 
sisting, literally,  of  a  pile  or  column  of 
metallic  plates  of  zinc  and  copper  and 
discs  of  wet  card,  placed  in  succession 
to  one  another  in  a  regular  order 
throughout  the  series. 

1.  Dry  Pile.  This  apparatus,  also 
called  ZambonVs  pile,  after  its  inventor, 
differs  from  the  hydro  electric  batteries 
principally  in  this,  that  the  presence  of 
the  electromotive  liquid  is  dispensed 
with,  its  place  being  occupied  by  some 
moist  substance  of  low  conducting  power, 
generally  paper.  It  agrees,  therefore, 
mainly  with  the  description  given  above, 
and  the  term  "  dry  "  is  inappropriate. 
230 


2.  Pile  of  two  elements  only.  This 
apparatus,  also  an  invention  of  Zamboni, 
consists  of  one  metal  and  one  interme- 
diate conductor,  either  dry  or  moist. 
These  piles  acquire  at  their  poles  a  feeble 
electrical  tension,  the  metallic  pole  ex- 
hibiting positive  electricity  in  the  dry 
pile,  and  the  pointed  end  of  the  metal 
being  positively  electrified  in  the  moist 
pile. 

3.  Secondary  piles.  These,  sometimes 
called  Rater's  piles,  consist  of  alternate 
layers  of  homogeneous  metallic  plates, 
between  which  some  moist  conducting 
substance  is  interposed.  When  they 
stand  alone,  no  electromotive  tension  is 
excited ;  but  they  are  capable  of  receiv- 
ing a  charge  by  being  placed  in  the  cir- 
cuit of  a  powerful  Voltaic  battery,  and  of 
thus  acquiring,  though  in  an  inferior  de- 
gree, the  properties  of  the  battery  itself. 

4.  Pile  of  Be  Luc.  An  electrical 
column,  constructed  of  pieces  of  paper, 
silvered  on  one  side,  and  alternating 
with  thin  leaves  of  zinc;  the  silvered 
surfaces  of  the  paper  discs  being  always 
in  the  same  direction. 

PILEUS.  The  cap ;  the  botanical 
term  for  the  uppermost  part  of  an  agaric, 
resembling  an  umbrella  in  form. 

PILI'DIUM.  The  orbicular  hemisphe- 
rical shield  of  lichens,  the  outside  of 
which  changes  to  powder,  as  in  calycium. 

PILOSITY  (pilosus,  hairy).  A  term 
applied  to  that  kind  of  hairiness  in 
plants,  in  which  the  hairs  are  long,  soft, 
and  erect,  as  in  the  carrot. 

PPM  ELITE.  A  green  silicious  earthy 
substance,  which  accompanies  chryso- 
prase,  and,  like  it,  owes  its  colour  to 
oxide  of  nickel.  It  is  a  variety  of  stea- 
tite, found  at  Kosemutz  in  Silesia. 

PINCHBECK.  An  alloy  of  copper,  or 
brass,  and  zinc,  made  in  imitation  of 
gold.  It  is  sometimes  called  tombac, 
similor,  and  petit-or. 

PINIC  ACID  (pinus,  the  pine).  An 
acid  obtained  from  rosin  ;  it  may  be  re- 
garded as  an  oxide  of  oil  of  turpentine. 

PINION.  A  wheel  consisting  of  fewer 
teeth  than  that  which  it  drives.  The 
teeth  of  a  pinion  are  called  leaves. 

PI'NITE.  A  talcose  substance,  con- 
sisting of  silica,  alumina,  and  oxide  of 
iron ;  found  in  granite  and  in  porphyry. 
By  Kirwan  it  is  called  micarelle. 

PINNATE  LEAF  (pinna,  a  feather, 
a  fish's  fin).  That  form  of  leaf  in  which 
simple  leaflets  are  placed  on  each  side  of 
a  common  petiole.  The  same  modifica- 
tions occur  as  in  the  palmate  leaf,  with 


PIS 


PLA 


similar  terms,  as  pinnatifid,  pinnatipar- 
tite,  pinnatisected,  and  pinnatilobate. 
A  pinnate  leaf  which  has  no  terminal 
leaflet  or  tendril,  is  said  to  be  equally  or 
abruptly  pinnate. 

PFNNATIPEDS  {pinna,  a  fin,  pes,  the 
foot).  An  order  of  birds  which  have  the 
digits  bordered  by  membrane. 

PINNOTHE'RIANS.  A  tribe  of  the 
third  family  of  the  brachyurous  crusta- 
ceans in  the  arrangement  of  Milne 
Edwards,  named  from  the  genus  pin- 
notheres, and  characterized  by  their  pecu- 
liar habit  of  being  housed  between  the 
mantle-lobes  of  certain  conchifers,  as  of 
mytilus,  pinna,  &c. 

PIPE-CLAY.  A  plastic  and  tenacious 
variety  of  clay,  of  a  greyish- white  colour, 
with  an  earthy  fracture,  and  a  smooth 
greasy  feel ;  found  near  Poole  in  Dorset- 
shire. 

PIPERA'CEiE.  The  Pepper  tribe  of 
dicotyledonous  plants.  Shrubs  or  herba- 
ceous plants,  with  leav es  opposite ;  flowers 
achlamydeous ;  stamens  adhering  to  the 
base  of  the  ovarium,  which  is  superior 
and  one-celled. 

PI'PRIDjE.  The  name  given  by  Mr. 
Vigors  to  a  family  of  the  Dentirostres, 
from  the  genus  Pipra.  Mr.  Swainson, 
rejecting  this  family,  gives  the  name 
Piprinae  to  the  manakins,  whicli  he 
makes  a  sub-family  of  the  Ampelidae, 
Fruit-eaters,  or  Chatterers. 

PISCES  {piscis,  a  fish).  The  first 
class  of  the  Vertebrata  or  Encephalata, 
consisting  of  fishes,  or  oviparous  ani- 
mals, inhabiting  the  water,  breathing  by 
means  of  permanent  branchiae,  and  hav- 
ing fins  for  progressive  motion.  See 
Ichthyology. 

PISCES  (in  Astronomy).  The  twelfth 
and  last  of  the  zodiacal  constellations, 
consisting  of  113  stars.  It  denoted  the 
third  month,  extending  from  the  20th  of 
August  to  the  20th  of  September.  During 
this  period,  the  inundation  of  the  Nile 
spreads  over  the  whole  of  Egypt,  and  the 
fishes  move  about. 

PISCIS  AUSTRALIS.  The  Southern 
Fish ;  a  constellation,  consisting  of 
twenty-four  stars,  the  principal  of  which 
is  Fomalhaut. 

PISCIS  VOLANS.  The  Flying-fish; 
a  modern  southern  constellation,  con- 
sisting of  eight  stars. 

PI'SOLITE  (7uW,apea,  MOo?,  stone). 
A  variety  of  carbonate  of  lime,  possess- 
ing a  structure  like  that  of  an  aggluti- 
nation of  pease.  It  occurs  in  the  middle 
Oolite  Formation. 
261 


PFSTACITE.  The  name  given  by 
Werner  to  some  mineral  substances,  now 
more  generally  designated  by  the  name 
of  epidote,  a  sub-species  of  prismatoidal 
augite. 

PISTIL  {pistillum,  a  pestle).  The 
name  given  by  botanists  to  the  female 
apparatus  in  plants.  It  occupies  the 
centre  of  the  flower,  and  is  distinguished 
into  three  parts;  viz.  the  ovary,  the 
style,  and  the  stigma. 

PISTON.  A  short  plug  of  metal,  or 
other  solid  substance,  fitted  exactly  to 
the  cavity  of  the  barrel  or  body  of  a  pump. 
It  serves  the  purpose  of  exhausting  the 
air  from  the  barrel,  and  is  hence  com- 
monly called  the  sucker.  There  are  two 
kinds  of  pistons  used  in  pumps,  the  one 
with  a  valve,  and  the  other  without  a 
valve,  called  a,  forcer  or  plunger. 

PIT  COAL.  Common  coal ;  so  called 
from  its  being  obtained  by  sinking  pits 
in  the  ground. 

PITCH-ORE.  The  hydrous  protoxide 
of  uranium,  also  called  indivisible  ura- 
nium; found  in  primitive  rocks. 

PITCHSTONE.  A  quartzose  rock,  of 
a  uniform  texture,  belonging  to  the  un- 
stratified  and  volcanic  classes,  which  has 
an  unctuous  appearance  like  that  of  in- 
durated pitch. 

PITTACAL  (tti'tto,  pitch,  jca\6f, 
beautiful).  A  beautiful  blue  colouring 
matter,  discovered  in  the  oil  of  tar. 

PITTED  TISSUE.  Bothrenchyma.  A 
variety  of  the  cellular  tissue  of  plants,  hav- 
ing its  sides  marked  by  pits,  sunk  in  the 
substance  of  the  composing  membrane. 
It  was  formerly  designated  by  the  term 
dotted  ducts,  vasiform  tissue,  &c. 

PI'TTIZITE.  Pitchy  iron  ore;  a 
variety  of  bog  iron  ore  found  near  Li- 
moges in  France. 

PLACE'NTA.  In  Botany,  that  part 
of  the  ovary  from  which  the  ovules  arise. 
It  generally  occupies  the  whole  or  a 
portion  of  one  angle  of  each  cell.  It  is 
sometimes  elongated  in  the  form  of  a 
little  cord,  called  the  umbilical  cord,  as 
in  the  hazel. 

PLAGIO'STOMI  (TrAcrytop,  transverse, 
(no/da.  a  mouth).  An  order  of  cartilagi- 
nous Fishes,  which  have  tneir  mouth 
placed  transversely  beneath  the  snout. 

PLANE,  or  PLANE  SURFACE.  In 
geometry,  this  is  a  surface  such  that  the 
right  line,  which  joins  every  two  points 
which  can  be  assumed  upon  it,  lies  en- 
tirely in  the  surfa'-e.  Hence,  a  plane 
rectilineal  figure  is  any  portion  of  a  plane 
surface  which  is  included  by  right  lines, 


PL  A 


PL  A 


and  the  figure  is  trilateral,  quadrilateral, 
multilateral,  &e.,  according  as  it  has 
three,  four,  or  many  sides. 

1.  Plane,  vertical.  A  plane  which 
passes  through  the  zenith,  or  point  which 
is  directly  over  our  heads,  and  the  centre 
of  the  earth,  is  called  a  vertical  plane, 
and  the  circle  in  the  heavens  marked  hy 
such  a  plane,  is  a  vertical  circle,  or 
azimuth. 

2.  Plane,  Tangential.  A  plane  which 
touches  a  curvilineal  solid.  It  is  from 
such  a  plane  that  angles  of  incidence  are 
measured,  whether  the  impinging  rays 
be  reflected  or  refracted. 

3.  Plane,  inclined.  In  Statics,  this 
term  denotes  a  plane  inclined  to  the  hori- 
zon. It  is  used  as  a  mechanical  power, 
and  the  problem  is  to  find  the  force 
necessary  to  prevent  a  body  placed  upon 
it  from  sliding  down  under  the  action  of 
its  own  weight. 

4.  Plane  of  Floatation.  The  surface  of 
a  heavy  fluid  at  rest  is  a  horizontal  plane, 
and  the  portion  of  this  plane  which  we 
may  imagine  to  be  within  a  floating  body, 
is  called  the  plane  of  floatation. 

5.  Plane  of  Vibration.  It  is  assumed 
that  in  polarized  light  the  particles  of 
ether  vibrate  only  in  two  opposite  direc- 
tions; the  plane  in  which  these  excur- 
sions take  place  is  called  the  plane  of 
vibration;  and,  if  a  plane  be  conceived  to 
be  situated  at  right  angles  to  the  plane  of 
vibration,  and  in  the  direction  of  the 
ray,  this  will  be  its  plane  of  polariza- 
tion. 

PLA'NET  (n\avf]Tm,  a  wanderer).  A 
star  which  is  found  to  change  its  relative 
situation  among  the  other  stars.  Planets 
are  distinguished,  with  reference  to  their 
centres  of  revolution,  into  primary  and 
secondary.  Primary  planets  are  those 
which  revolve  round  the  sun  as  a 
centre ;  secondary  planets,  more  fre- 
quently called  satellites  or  moons,  are 
those  which  revolve  round  a  primary 
planet  as  a  centre,  and  are  carried  with 
it  in  its  revolution  round  the  sun. 

1.  The  Primary  Planets  are  divided 
into  superior  and  inferior.  The  superior 
are  those  more  remote  from  the  sun  than 
the  earth,  as  Mars,  Jupiter,  Saturn, 
Herschel,  and  Neptune.  The  inferior 
are  those  which  are  nearer  to  the  sun 
than  the  earth,  as  Mercury  and  Venus. 
See  Asteroids. 

2.  The  following  symbols  are  employed 
to  designate  the  planets  in  tables  and  on 
globes.  Mercury  §,  Venus  $,  the 
Earth  0,   Mars  <£,   Vesta  S,   Juno  £, 

2C2 


Ceres  <j>,  Pallas  $  ,  Jupiter  If.,  Saturn  r\, 
Herschel  or  Uranus  H. 

3.  Two  planets  are  in  conjunction 
when  they  have  the  same  longitude ; 
they  are  in  opposition  when  their  longi- 
tudes differ  by  180°. 

PLANETARY  PERIOD.  The  period 
in  which  a  planet  comes  again  into  the 
position  which  it  occupied  at  first  with 
respect  to  the  sun.  The  motions  of  the 
planets  being  oscillatory,  a  planetary 
period  is  not  that  in  which  a  planet  re- 
volves round  the  heavens,  but  a  repe- 
tition of  such  periods.  For  instance, 
when  Mercury  has  just  repeated  the 
circuit  of  the  earth's  visible  heaven,  he 
is  not  in  the  same  position  with  respect 
to  the  sun  as  at  the  beginning.  The 
cycle  of  relative  positions  is  not  com- 
pleted, for  this  planet,  in  less  than  thir- 
teen years  and  three  days,  or  two  days 
if  there  be  four  leap  years  in  the  period. 
So,  in  a  watch,  the  cycle  of  relative  posi- 
tions of  the  minute  and  the  hour  hand  is 
not  repeated  every  hour,  but  in  every 
twelve  hours. 

PLANIPE'NNES.  One  of  the  sec- 
tions of  Insects  into  which  Latreille 
divides  the  order  Neuroptera.  There 
are  four  families :  viz.,  the  panorpidae, 
the  myrmeleonidae,  the  hemerobiidae, 
and  the  perlidae. 

PLA'NISPHERE.  An  old  term  for 
any  representation  of  the  sphere  upon  a 
plane.  It  now  denotes  any  contrivance 
by  which  plane  surfaces  moving  on  one 
another  fulfil  any  of  the  uses  of  a  ce- 
lestial globe. 

PLANTI'GRADA  {p/anta,  the  sole  of 
the  foot,  gradior,  to  walk).  A  division 
of  the  terrestrial  Carnivorous  animals, 
which,  in  walking,  apply  the  entire  sole 
of  the  foot  to  the  ground,  as  far  back  as 
the  end  of  the  os  calcis  ;  as  the  bear,  the 
badger,  &c.    See  Digitigrada. 

PLASMA.  A  scarce  green  semitrans- 
parent  chalcedony,  of  a  dark  tint,  sup- 
posed to  be  coloured  by  chlorite. 

PLASTER  OF  PARIS.  Sulphate  of 
lime,  or  gypsum,  heated  in  an  oven  till 
nearly  anhydrous,  and  then  reduced  to 
powder.  On  adding  water,  an  artificial 
hydrate,  or  stucco,  is  formed,  which  sets 
in  a  short  time,  and  has  the  same  com- 
position as  native  gypsum. 

PLASTIC  CLAY  (yrbdaraia,  to  fashion). 
One  of  the  beds  of  the  Eocene  Tertiary 
Period,  named  from  its  being  used  in 
the  manufacture  of  pottery.  The  term 
is  applied  to  a  series  of  beds,  chiefly 
sands,  with  which  the  clay  is  associated. 


PLE 


PLI 


It  skirts  the  London  clay  within  the 
London  chalk  basin,  and  appears  also  in 
the  Isle  of  Wight. 

PLATEAU.  A  terra  often  exclusively 
applied  to  an  elevated  plain  ;  it  is,  how- 
ever, sometimes  used  to  denote  a  great 
extent  of  country  considerably  raised 
above  the  rest  of  (he  land,  and  having 
its  mountains,  plains,  and  valleys  ;  as  in 
the  minor  plateau  of  Albania,  and  the 
great  plateau  of  Central  Asia.  See 
Table  Land. 

PLATFORM.  When  a  mountain  ap- 
pears as  if  its  summit  were  cut  off, 
leaving  a  level  and  horizontal  surface,  it 
forms  a  platform,  or  is  said  to  be  trun- 
cated.    See  Mountain. 

PLATINUM  { plata,  silver).  A  white 
metal  found  in  the  auriferous  sand  of 
certain  rivers  in  America.  Reduced  to 
a  state  of  extreme  division,  it  has  the 
appearance  of  sponge;  and  it  is  then 
called  spongy  platinum,  and  is  used  as  a 
pyrophorus. 

PLECTO'GNATHI  (7r\eK-r6?,  twisted, 
yvdOov,  a  jaw).  An  order  of  Fishes,  in 
which  the  bones  of  the  upper  jaw  are 
united  to  each  other  and  to  the  head. 

PLEI'OCENE  UXeiW,  more,  Katv6r, 
recent).  By  the  terms  Older  and  Newer 
Pleiocene,  are  denoted  two  divisions  of 
the  Tertiary  Period  which  are  the  most 
modern,  and  of  which  the  largest  part  of 
the  fossil  shells  are  of  recent  species. 
The  newer  formation  is  also  termed 
pleistocene. 

PLEIOSAU'RUS  (7rXe/a>v,more,  aavpa, 
a  lizard).  A  species  of  animal,  the  re- 
mains of  which  are  found  in  some  of  the 
clay  beds  of  the  oolites ;  it  seems  to  have 
been  intermediate  between  the  plesio- 
saurus  and  the  ichthyosaurus  ;  the  teeth, 
vertebrae,  bones  of  the  extremities,  &c, 
being  more  like  the  corresponding  parts 
of  the  former,  but  the  animal  resembles 
the  latter  in  the  absence  of  apparent 
neck ;  and  from  this  greater  analogy 
with  reptiles  it  has  received  its  name. 

PLEPSTOCENE  (  ttXcIo-toc,  most, 
Kaii/6?,  recent).  The  newest  of  the  ter- 
tiary strata,  which  contain  the  largest 
proportion  of  living  species  of  shells. 

PLE'ONASTE.  Ceylonite.  An  alu- 
minate  of  protoxide  of  iron  and  mag- 
nesia. 

PLESIOSAU'RUS  {nXnalov,  near  to, 
<ravpa,  a  lizard).  An  extinct  genus  of 
Saurian  reptiles,  which  united  to  the 
head  of  a  Lizard  the  teeth  of  a  Croco- 
dile; a  neck  of  enormous  length,  re- 
sembling the  body  of  a  serpent ;  a  trunk 
263 


and  tail  having  the  proportions  of  an 
ordinary  quadruped,  the  ribs  of  a  Chame- 
leon, and  the  paddles  of  a  Whale.  They 
appear  to  have  lived  in  shallow  seas 
and  estuaries,  and  to  have  breathed  air 
like  the  Ichthyosauri  and  our  modern 
Cetacea. 

PLEURE'NCHYMA  (wXewpo,  the 
side,  ?7xuMa>  infusion).  A  designation  of 
the  woody  tissue  of  plants,  consisting  of 
very  slender,  tough,  transparent,  mem- 
branous tubes,  tapering  acutely  to  each 
end,  lying  in  bundles,  and  communi- 
cating with  one  another  by  invisible 
pores. 

PLEURONE'CTIMI  ( pleuronectes, 
the  flounder;  from  irXevpa,  the  side, 
vnKrij?,  a  swimmer).  The  Flat-fish  or 
Flounder  tribe  ;  a  family  of  Malacopte- 
rygious  or  soft  spined  fishes,  characterized 
by  extreme  flattening  of  the  body,  and 
by  deficiency  of  symmetry.  The  term 
pleuronectes,  or  side-finned,  is  calculated 
to  produce  an  erroneous ;  opinion  what 
are  usually  called  the  belly  and  back  of 
these  fishes  being  actually  the  sides, 
though  differing  remarkably  in  colour. 

PLEURO'PTERA  (nXevpa,  the  side, 
mepov,  a  wing).  A  tribe  of  quadrupeds, 
generally  known  as  Flying  Lemurs, 
Flying  Cats,  and  Flying  Foxes.  They 
are  generally  arranged  under  the  order 
Carnassiers,  and  are  placed  by  some 
zoologists  in  the  division  Cheiroptera. 

PLEUROTOMA'RIiE.  A  sub-family 
of  the  Trochidce,  named  from  the  pleu- 
rotomaria,  a  fossil  trochiform  shell, 
having  a  slit  in  the  outer  lip. 

PLEUROTO'MINjE.  The  slit-shells ; 
a  sub-family  of  the  Strombidcs,  or  Wing- 
shells,  named  from  the  typical  genus 
pleurotoma,  and  characterized  by  a  deep 
lobe,  or  slit,  at  the  top  of  the  outer  lip  ; 
the  spire,  in  general,  is  very  long  and 
the  shells  themselves  often  spindle- 
shaped. 

PLI'CIPENNES  {plica,  a  fold,  penna, 
a  wing).  The  third  section,  according  to 
Latreille,  of  the  Neuropterous  insects. 
They  constitute  the  genus  phryganea, 
and  are  known  by  the  name  of  caddis- 
worm.  They  form  the  order  Trichoptera 
in  the  system  of  Kirby  and  Spence. 

PLINLIMMON  ROCKS.  A  subordi- 
nate group  of  the  Cambrian  series,  con- 
sisting of  the  greywacke  of  various 
qualities ;  it  corresponds  with  the  Grey- 
wacke Range  of  the  Lammermuir,  ex- 
tending from  St.  Abb's  Head,  on  the  east 
coast  of  Scotland,  to  the  Mull  of  Gallo- 
way. 


POD 


POI 


PLOMB  GOMME.  Hydrated  alu- 
minate  of  lead,  found  in  the  French  de- 
partment of  Cote  du  Nord. 

PLOPOCA'RPIUM.  A  term  applied 
by  Desvaux  to  a  form  of  fruit,  consisting 
of  several  follicles  united  in  a  single 
flower,  as  in  nigella  and  delphinium. 

PLUMB A'GO.  Carburet  of  iron;  a 
mineral,  also  known  as  graphite  and 
blacklead,  occurring  in  rounded  masses 
deposited  in  beds  in  the  primitive  forma- 
tions, particularly  in  granite,  mica-schist, 
and  primitive  limestone.  Borrowdale  in 
Cumberland  is  a  celebrated  locality  of 
graphite,  and  affords  the  only  specimens 
which  are  sufficiently  hard  for  making 
pencils. 

PLUMBER'S  SOLDER.  An  alloy  of 
one  part  of  tin  and  two  of  lead. 

PLUMBOCA'LCITE.  A  mineral  sub- 
stance in  which  the  oxide  of  lead  occurs 
in  the  form  of  carbonate  of  lime;  an 
isomorphism  by  which  the  protoxide  of 
lead  is  connected  with  the  magnesian 
oxides. 

PLUMULE  (plumula,  a  little  feather). 
Gemmule.  The  ascending  part  of  the 
axis  of  the  embryo  of  a  seed. 

PLUTO'NIC  ACTION.  The  influence 
of  volcanic  heat  and  other  subterranean 
causes  under  pressure. 

PLUTONIC  ROCKS.  A  designation 
of  granite,  porphyry,  and  other  igneous 
rocks,  supposed  to  have  been  consoli- 
dated from  a  melted  state  at  a  great 
depth  from  the  surface,  aud  named  from 
Pluto,  the  fabled  God  of  the  infernal 
regions.  The  term  unstratified  is  also 
applied  to  this,  the  first  class  of  rocks. 

PLUVIO'METER  (pluvius,  rain, 
fierpov,  a  measure).  A  rain-gauge;  a 
vessel  for  catching  falling  rain,  in  order 
to  determine  what  quantity  of  rain  has 
fallen  in  a  given  period. 

PNEUMATICS  {itveviia,  wind).  That 
branch  of  natural  philosophy  which  treats 
of  the  mechanical  properties  of  air  and 
other  compressible  fluids.  The  term 
pneumatology  was  once  employed  for 
metaphysics. 

PNEUMOBRANCHIA'TA  (ffveu/xa, 
air,  f3pdyxia>  gi^s)-  Under  this  term, 
Lamarck  arranges  several  genera  of 
Molluscous  animals  into  a  section,  which 
connects  his  second  order  Hydrobranchia 
with  his  third  order  Tracheli-podes.  The 
genera  are  onchidium,  parmacella,  limax, 
testacellus,  and  vitrina. 

PODE'TIUM  (7rcn;f,  Trodor,  afoot).  A 
little  foot;  the  stalk-like  elongation  of 
the  thallus,  which  supports  the  fructifi- 
264 


cation  of  the  Cenomyce,  a  plant  of  the 
order  of  the  Lichens. 

PODOGY'NIUM  (ttovp,  7rod6f,  a  foot, 
fwrj,  a  female).  A  term  applied  to  the 
stalk  upon  which  the  ovary  i3  seated  in 
certain  plants,  as  the  Passiflora,  Tac- 
sonia,  &c.  It  is  also  called  gynophore, 
and  thecaphore. 

PODOPHTHA'LMIA  ( Troup,  ttooop, 
a  foot,  b<p0a\u6s,  the  eye).  A  group  of 
the  malacostracous  Crustacea,  which  have 
moveable  pedunculated  eyes.  It  contains 
two  orders;  the  Decapods  and  the  Sto- 
mapods.     See  Edriopthalmia. 

PODOSPE'RMIUM  (ttoup,  7to3oP,  a 
foot,  o-7rep/Lia,  seed).  A  term  applied  by 
some  writers  to  the  funiculus  or  umbili- 
cal cord,  by  which  the  ovule  of  plants  is 
connected  with  the  placenta. 

PODU'RIDiE.  A  family  of  wingless 
insects,  belonging  to  the  order  Thysa- 
noura,  in  which  the  extremity  is  pro- 
longed into  a  forked  tail,  as  in  the 
podura. 

PCECILO'PODA  (7ro£Ki'\op,  various, 
ttoup,  a  foot).  A  designation  of  the  low- 
est forms  of  the  Crustacea,  from  the  an- 
isopodous  character  of  their  segments, 
the  feet  of  different  segments  being  pre- 
hensile, or  natatory,  or  branchial,  or 
ambulatory. 

POIKILI'TIC  (ttoiki'Xop,  variegated). 
A  term  sometimes  applied,  in  geology,  to 
the  New  Red  Sandstone  formation,  owing 
to  the  varieties  of  colours  which  it  pre- 
sents. 

POINT.  A  physical  point  is  the 
smallest  magnitude  perceptible  by  the 
senses.  If  such  a  point  be  supposed  to 
be  infinitely  diminished,  an  idea  is 
formed  of  a  mathematical  point,  of  which 
we  may  say  that  it  has  "no  parts."  As 
a  mathematical  line  may  be  conceived  to 
proceed  from  the  motion  of  a  mathema- 
tical point,  so  a  physical  line  may  be 
conceived  to  be  generated  by  the  motion 
of  a.  physical  point. 

Point  of  Contrary  Flexure.  A  point 
at  which  a  curve  changes  its  curvature 
with  respect  to  any  given  external  point, 
being  concave  on  one  side  and  convex 
on  the  other. 

POINTS  OF  THE  COMPASS.  Besides 
the  cardinal  points,  North,  South,  East, 
and  West,  intermediate  directions  are 
adopted  by  seamen  and  travellers, 
amounting  in  all  to  thirty-two  primary 
directions,  each  of  which  is  called  a 
point  of  the  compass,  and  thence  the 
interval  between  them,  or  the  angle  from 
point  to  point,  is  also  called  a.  point. 


POL 


POL 


1.  The  first  sixteen  of  these  interme- 
diate points  are  named  as  follows  I — 
Half-way  between  north  and  east,  is 
North-East  (n.e.)  ;  and  similarly  are 
explained  South-east,  South-west,  and 
North-West  (s.e.,  s.w.,  n.w.).  Again, 
half-way  between  North  and  North-East 
is  North-North-East  (n.n.e.);  and  thus 
are  explained  East- North-East,  East- 
South- East,  South-South-East,  South- 
South-West,  West-South-West,  West- 
North-West,  North-North-West  (e.n.e., 

E.S.E.,     S.S.E.,      S.S.W.,     W.S.W.,     W.N.W., 

N.N.W.). 

2.  These  sixteen  are  subdivided,  the 
new  and  final  subdivisions  being  de- 
scribed each  by  the  simplest  of  the  two 
adjacent  directions,  and  the  cardinal 
direction  in  which  that  last  direction  is 
left.  Thus,  North-East  by  North  means 
the  direction  next  to  North-East  in  going 
towards  the  north,  and  comes  between 
n.e.  and  n.n.e.  By  the  same  rule, 
North-east  by  North  might  be  called 
North-North-East  by  East,  but  the  former 
is  the  more  simple. 

3.  The  angle  of  revolution  from  one 
point  to  the  next  is,  of  course,  the  32nd 
part  of  360°,  or  \\\°,  and  it  is  sometimes 
customary  to  insert  fractions  of  a  point; 
thus  n.n.e Je.,  means  a  quarter  of  a 
point  eastward  from  n.n.e. 

POLAR  CIRCLES.  Two  circles, 
North  and  South,  Arctic  and  Antarctic, 
described  by  the  earth  in  its  diurnal 
rotation,  and  so  named  from  their  proxi- 
mity to  the  two  poles,  from  which  they 
are  at  the  same  distance  as  the  tropics 
are  from  the  equator,  viz.  23£  degrees. 
These  polar  circles  bound  those  portions 
of  the  earth  where  it  is  continuous  day 
and  night  during  several  diurnal  revolu- 
tions of  our  planet.  On  the  terrestrial 
globe  these  circles  surround  the  frozen 
zones. 

PO'LARISCOPE.  An  instrument  con- 
trived for  the  exact  and  convenient  ob- 
servation of  the  phenomena  of  polarized 
light,  and  also  for  the  measurement  of 
the  angle  of  polarization. 

POLA'RITY.  A  term  applied,  in  its 
most  comprehensive  sense,  to  a  body 
possessing  certain  powers  which  are  not 
general,  but  local,  and  not  the  same,  but 
opposite.  It  is  more  particularly  applied 
to  the  magnet,  the  attractive  power  of 
which  is  not  possessed  in  an  equal  de- 
gree by  every  particle  composing  the 
magnet,  but  is  chiefly  localized  in  two 
points  at  or  near  its  extremities ;  fur- 
ther, the  powers  residing  in  these  points 
2fi5 


are  not  one  and  the  same,  but  different 
—indeed  contrary  in  their  nature,  and 
are  distinguished  by  the  different  names 
of  Boreal  magnetism  and  Austral  mag- 
netism. These  two  points  are  called  the 
poles  of  the  magnet,  and  the  right  line 
joining  them  is  the  axis. 

1.  Polarity,  Chemical.  The  principle 
just  stated  has  been  applied  to  the  che- 
mical phenomena  of  the  voltaic  circle. 
The  zinc  and  hydrochloric  acid  are 
equally  supposed  to  have  a  polarizable 
molecule:  one  pole  of  each  molecule  has 
the  attraction,  or  affinity,  which  is  cha- 
racteristic of  zinc,  or  zincous  attraction, 
and  is  called  the  zincous  pole ;  while  the 
other  has  the  attraction,  or  affinity,  which 
is  characteristic  of  chlorine,  or  chlorous 
attraction,  and  is  called  the  chlorous 
pole.  Polarity  is  not  an  ordinary  condi- 
tion of  the  particles  of  either  the  zinc  or 
the  acid  ;  but  is  developed  in  both  when 
brought  into  contact  with  each  other. 

2.  Two  Polarities.  A  term  expressive 
of  two  antagonist  energies,  each  of  which 
repels  that  which  is  similar,  and  attracts 
that  which  is  opposite,  to  itself.  Thus,  the 
two  north  or  two  south  poles  of  two  mag- 
netic needles  mutually  repel  each  other; 
but  the  north  pole  of  one  needle,  and  the 
south  pole  of  another,  mutually  attract 
each  other. 

3.  Reversion  of  Terms.  The  earth  it- 
self being  considered  as  a  magnet,  or  as 
containing  within  itself  a  powerful  mag- 
net, lying  in  a  position  nearly  coinciding 
with  its  axis  of  rotation,  the  south  pole  of 
a  magnetic  needle  would  point  towards 
the  north  pole  of  the  earth ;  so  that  the 
north  end  is  the  south  pole,  and  the  south 
end  the  north  pole  of  a  magnetic  needle. 

4.  Boreal  and  Austral  Polarities.  To 
avoid  the  above  confusion  of  terms,  the 
words  Boreal  and  Austral  have  been 
applied  to  the  magnetism  of  the  earth, 
while  the  terms  North  and  South  have 
been  restricted  to  that  of  the  needle  ; 
what  had  been  called  northern  polarity 
being  now  Austral  polarity ;  what  had 
been  called  southern,  being  Boreal  po- 
larity. 

5.  Chemical  and  Cohesive  Polarities. 
Two  hypothetical  forces,  supposed  by 
Dr.  Prout  to  reside  in  the  ultimate  mole- 
cules of  matter ;  the  chemical  being  of  a 
binary  character,  existing  between  mole- 
cule and  molecule,  and  chiefly  between 
molecules  of  different  matter ;  the  cohe- 
sive determining,  under  certain  circum- 
stances, the  cohesion  of  the  molecules 
of  the  same  matter. 

N 


POL 


POL 


POLARIZED  LIGHT.  A  ray  of  light 
is  said  to  be  polarized,  when,  after  its 
emergence  from  the  substance,  or  reflec- 
tion from  the  surface,  of  a  body,  it  ac- 
quires poles  or  sides  with  different  pro- 
perties in  relation  to  the  plane  of  its 
incidence.  Polarized  light  is  procured — 
1.  by  reflection  from  the  surfaces  of 
transparent  and  of  opaque  bodies  ;  2.  by 
transmission  through  several  plates  of 
uncrystallized  bodies ;  and,  3.  by  trans- 
mission through  bodies  regularly  crystal- 
lized, and  possessing  the  property  of 
double  refraction,  as  Iceland  spar. 

POLE  (TToXew,  to  turn).  The  extre- 
mity of  the  axis  of  a  circle.  The  extre- 
mities of  the  axis  of  the  earth  are  termed 
the  poles,  and  are,  respectively,  the 
north  and  south— the  Arctic  and  Ant- 
arctic—poles  of  our  globe.  The  earth's 
axis,  being  extended  each  way,  becomes 
an  axis  to  the  spherical  concavity  of  the 
sky,  and  its  extremities  are  the  north 
and  south  poles  of  the  heavens.  See 
Axis. 

Pole  of  revolution.  When  a  globe  re- 
volves about  one  of  its  diameters,  each 
extremity  of  that  diameter  is  called  a 
pole  of  revolution.  Every  point  of  the 
sphere  describes  either  the  great  circle 
which  has  the  poles  of  revolution  for  its 
poles,  or  one  of  the  parallels  of  that 
great  circle. 

POLE-STAR,  or  POLAR  STAR.  A 
bright  star  of  the  second  magnitude,  in 
the  tip  of  the  tail  of  the  northern  con- 
stellation Ursa  Minor,  or  the  Little  Bear ; 
it  is  named  from  its  proximity  to  the 
north  pole  of  the  heavens,  the  only  one 
visible  in  our  latitude. 

PO'LEMOSCOPE  (TToXejuor,  war,  <tko- 
Trew,  to  view).  An  instrument,  invented 
by  Hevelius,  for  viewing  objects  which 
cannot  be  seen  by  direct  vision.  It  con- 
sists of  a  perspective  glass,  having  a 
reflector  placed  at  an  angle  of  45°  to  its 
axis,  so  that  any  object  falling  on  the 
reflector  is  conveyed  to  the  eye.  The 
name  suggests  that  a  person  might,  by 
means  of  such  an  instrument,  observe, 
from  a  place  of  concealment,  what  is 
going  on  in  an  enemy's  camp. 

POLITICAL  ECONOMY.  That  branch 
of  political  science  which  relates  to  the 
production  and  accumulation  of  wealth, 
its  distribution  and  consumption.  It  is, 
in  short,  to  the  state  what  private  eco- 
nomy is  to  the  single  family. 

POLLEN.  The  organic  matter  by 
which  impregnation  is  effected  in  the 
vegetable  kingdom.  It  consists  of  fine 
266 


powder,  or  grains,  enclosed  within  the 
anther.  Each  grain,  when  mature,  and 
brought  into  contact  with  the  stigmatic 
tissue,  emits  a  tube,  containing  a  fluid 
termed  fovilla,  which  is  charged  with 
molecular  matter.  The  pollen-masses  of 
Orchidaceous  and  Asclepiadaceous  plants 
consist  of  pollen-grains  cohering  into 
solid  waxy  masses. 

POLLUX.  A  star  of  the  second  mag- 
nitude, in  the  zodiacal  constellation  Ge- 
mini. The  same  name  is  also  given  to 
the  hindermost  twin,  or  posterior  part, 
of  the  same  constellation. 

POLY-,  POL-  (ttoXu?,  many).  A 
Greek  prefix,  denoting  many  or  much. 

1.  Pol-akenium.  A  term  applied  by 
Richard  to  a  fruit  consisting  of  several 
akenia  (see  Achcenium).  When  there  are 
two  cells,  the  fruit  is  a  di-akenium ;  when 
three,  a  tri-akenium ;  and  so  on. 

2.  Poly-adelphia  (ade\06?,  a  brother). 
The  eighteenth  class  of  plants  in  the 
Linnaean  system,  in  which  the  stamens 
are  associated  in  several  parcels,  or 
brotherhoods,  as  in  Hypericum. 

3.  Poly-andria  (avrjp,  a  man).  The 
thirteenth  class  in  the  Linnaean  system 
of  plants,  comprising  those  which  have 
more  than  twenty  stamens  inserted  be- 
neath the  ovarium. 

4.  Poly-basiie.  A  double  sulphuret  of 
silver  and  other  metals,  in  which  the 
sulphuret  of  silver  and  the  subsulphuret 
of  copper,  being  isomorphous,  replace 
each  other  in  indeterminate  proportions. 

5.  Poly-carpous  {Kapwds,  fruit).  A  term 
applied  to  a  plant  which  has  the  power  of 
bearing  fruit  many  times  without  perish- 
ing. Poly-carpous  plants  are  distinguished 
into  the  caulocarpous,  or  those  whose 
stem  endures  many  years,  constantly 
bearing  flowers  and  fruits,  as  trees  and 
shrubs;  and  the  rhizocarpous,  or  those 
whose  root  endures  many  years,  but 
whose  stems  perish  annually,  as  herba- 
ceous plants. 

6.  Poly-chorion  (%6ptov,  any  skin).  A 
term  applied  by  Mirbel  to  the  fruit  of 
the  ranunculus,  &c,  more  commonly 
known  by  the  term  etcerio. 

7.  Poly-chroite  (xpo<*i  colour).  The 
extractive  matter  of  saffron,  the  watery 
infusion  of  which  assumes  different  co- 
lours when  treated  with  different  agents. 

8.  Poly-clinum  (icKivti,  a  bed).  A  gene- 
ral term  applied  by  Cuvier  to  all  those 
forms  of  aggregated  tunicated  mollusca, 
which  agree  more  or  less  closely,  in  inter- 
nal structure,  with  the  salpae  and  as- 
cidians. 


POL 


POL 


9.  Poly-galacete.  The  Milkwort  tribe 
of  dicotyledonous  plants.  Shrubs  or  her- 
baceous plants  with  leaves  generally  alter- 
nate; flowers  polypetalous,  unsymme- 
trical ;  stamens  hypogynous  ;  ovary  2- 
celled ;  fruit  dehiscent. 

10.  Poly-gamia  {yano?,  nuptials).  The 
name  of  the  twenty-third  class  in  the 
Linnaean  system  of  plants,  comprising 
those  which  bear  hermaphrodite  and  uni- 
sexual flowers  on  the  same  individual ; 
or  hermaphrodites  on  one  individual, 
males  on  a  second,  and  females  on  a 
third. 

11.  Poly-gastrica  (yaaTt^p,  a  stomach). 
A  class  of  Radiated  animals,  having  nu- 
merous stomachs  or  cceca  communicating 
with  an  internal  alimentary  cavity,  with- 
out perceptible  nerves  or  muscles,  but 
moving  by  means  of  external  vibratile 
cilia. 

12.  Poly-yon  {ywvia,  an  angle).  A 
rectilinear  figure,  bounded  by  more  than 
four  sides.  Polygons  are  called  penta 
gons,  hexagons,  heptagons,  &c,  accord- 
ing as  they  are  bounded  by  five,  six, 
seven,  or  more  sides.  A  line  joining  the 
vertices  of  any  two  angles  which  are  not 
adjacent  is  called  a  diagonal  of  the  poly- 
gon. 

13.  Poly-gon  of  Forces.  A  theorem  in 
mechanics,  which  may  be  thus  stated: — 
If  any  number  of  forces  act  upon  a  point, 
and  a  polygon  be  taken,  one  of  the  sides 
of  which  is  formed  by  the  line  represent- 
ing one  of  the  forces,  and  the  following 
sides  in  succession  by  lines  representing 
the  other  forces  in  magnitude,  and 
parallel  to  their  directions,  then  the  line 
which  completes  the  polygon  will  repre- 
sent the  resultant  of  all  the  forces. 

14.  Poly-gonal  {ya>via,  an  angle).  A 
term  applied,  in  arithmetic,  to  certain 
numbers  possessing  this  property,  that 
the  same  number  of  points  may  be 
arranged  in  the  form  of  that  polygonal 
figure  to  which  they  belong.  SeeFigurate 
Number,  and  Number. 

15.  Poly-gonacece.  The  Buck-wheat 
tribe  of  dicotyledonous  plants,  herbace- 
ous plants  with  leaves  alternate  ;  flowers 
occasionally  unisexual ;  stamens  definite ; 
ovary  superior;  seed  with  farinaceous 
albumen. 

16.  Poly-gynia  {ywij,  a  woman).  The 
designation  of  those  orders  of  plants  in 
the  Linnaean  system,  in  which  there  is 
an  indefinite  number  of  stamens. 

17.  Poly-halite  (SXp,  salt).  A  chemical 
compound  of  several  sulphates,  formerly 
mistaken  for  anhydrous  sulphate  of  lime ; 

267 


compact  and  fibrous,  from  the  salt  forma- 
tion in  Bavaria  and  Austria. 

18.  Poly-hedron  (e<3pa,  a  seat  or  side). 
A  geometrical  solid  bounded  by  several 
faces  or  planes.  In  every  solid  poly- 
hedron, the  number  of  faces  and  corners 
exceeds  the  number  of  edges  by  two. 

19.  Poly-meric  (fxepos,  a  part).  A  term 
applied  in  chemistry  to  those  bodies 
which  contain  the  same  relative,  but  not 
the  same  absolute  number  of  atoms  of 
the  same  elements,  and  whose  atomic 
weights  are  consequently  unlike.  Several 
carburets  of  hydrogen  afford  examples  of 
polymerism.     See  Isomerism. 

20.  Poly-mignite.  Titaniate  of  iron ; 
a  new  mineral  found  sometimes  in  the 
zircon-syenite  of  Fredrickswarn  in  Nor- 
way. 

21.  Poly-nomial.  A  barbarous  word, 
sometimes  employed  in  algebra  for  mul- 
tinomial, and  denoting  a  quantity  of 
many  terms,  as  the  expression 

a  +  2  b  +  3  c  +  nd,  &c. 

22.  Poly-optron  {oirrpov,  a  looking- 
glass).  A  glass  for  multiplying  objects. 
It  consists  of  a  lens  one  side  of  which  is 
plane,  but  the  other  presents  several 
spherical  concavities,  each  of  which 
becomes  a  plano-concave  lens,  and  dimi- 
nishes the  object  viewed. 

23.  Poly-petalous  (neTaXov,  a  flower- 
leaf).  A  designation  of  that  kind  of 
corolla,  in  which  the  petals  are  separate 
from  one  another,  as  distinguished  from 
the  monopetalous  or  gamopetalous  co- 
rolla, in  which  the  petals  cohere. 

24.  Poly-phore  {<pepa>,  to  bear).  The 
name  given  by  Richard  to  the  succulent 
and  dilated  receptacle  of  such  plants  as 
the  strawberry  and  the  raspberry.  More 
commonly,  such  a  receptacle  is  suffi- 
ciently described  by  the  adjective  fleshy. 

25.  Poly-piaria.  Corals.  A  numerous 
class  of  invertebrated  animals,  belonging 
to  the  great  division  of  the  Radiata. 

26.  Poly-piphera.  A  class  of  the  Ra- 
diata, consisting  of  soft,  aquatic  animals 
of  a  plant-like  form,  which  develope  small 
tubular  digestive  sacs  called  polypi,  the 
margins  of  which  are  furnished  with  sen- 
sitive tentacula,  and  the  sides  of  the 
latter  with  vibratile  cilia. 

27.  Poly-podiacece.  One  of  the  prin- 
cipal divisions  of  the  natural  order  of 
Ferns,  constituting  the  highest  form  of 
acrogenous  plants,  and  exhibiting  the 
nearest  approach  to  the  Cycadaceous 
Gymnosperms. 

28.  Poly  pus  (novs,  no66t,  a  foot).  Un- 
der the  common  name  Polypi  have  been 

N2 


POR 


POR 


grouped  together  three  classes  of  Radi- 
ated animals,  on  account  of  their  external 
resemblance  to  the  many-armed  cuttle- 
fishes, which  were  so  denominated  by 
the  ancient  Greek  naturalists.  The  term 
now  denotes  a  class  of  Radiated  animals, 
furnished  with  numerous  prehensile  or- 
gans radiating  from  around  the  mouth. 

29.  Poly-scope  (o-KOTrew,  to  view).  A 
lens  plane  on  one  side,  and  convex  on 
the  other,  the  latter  being  formed  of  seve- 
ral plane  surfaces,  or  facettes,  for  the 
purpose  of  multiplying  any  object. 

30.  Poly-sepalous.  A  designation  of 
that  form  of  calyx,  in  which  the  sepals 
are  separate  from  one  another,  as  distin- 
guished from  the  monosepalous  or  gamo- 
sepa'ous  calyx,  in  which  the  sepals  co- 
here. 

31.  Poly-spermous  {a-nepfia,  seed).  Hav- 
ing many  seeds  ;  a  botanical  term  applied 
to  certain  fruits,  which  contain  many 
seeds,  and  distinguished  from  oligo- 
spermous,  or  few-seeded. 

32.  Poly-synthetic  (<rvv6e<ris,  a  putting 
together).  The  name  applied  by  Du 
Ponceau  to  the  class  of  languages  spoken 
by  the  Indian  tribes  of  America,  from 
the  manner  in  which  words  are  abbre- 
viated and  combined  to  express  ideas. 

33.  Poly-thalamaceans  {0d\afxo?,  a 
chamber).  The  name  given  by  De  Blain- 
ville  to  an  order  of  Cephalopods,  includ- 
ing all  those  which  inhabit  many-cham- 
bered shells. 

34.  Poly-zonal  (£an/»i,  a  belt).  Lite- 
rally, what  is  composed  of  many  zones, 
or  belts.  The  term  is  applied  to  certain 
lenses,  composed  of  pieces  united  in 
rings,  which  are  therefore  called  poly- 
zonal lenses. 

POMA'CEiE  (pomum,  an  apple).  The 
Apple  tribe  of  dicotyledonous  plants. 
Trees  or  shrubs  with  leaves  alternate; 
flowers  polypetalous ;  stamens  perigyn- 
ous  ;  fruit  1  to  5-celled. 

POME  (pomum,  an  apple).  A  fruit 
consisting  of  two  or  more  inferior  carpels 
united  together,  the  pericarp  being 
fleshy,  and  formed  of  the  floral  envelope 
and  the  ovary  closely  adhering. 

PO'NDERABLE  MATTER  (pondus, 
weight).  A  term  applied  to  all  bodies 
possessing  weight,  as  metals,  gases,  &c, 
as  distinguished  from  light,  heat,  and 
electricity,  which,  having  no  appreciable 
weight,  are  termed  imponderable  agents. 

PORCELAIN  CLAY.  A  species  of 
clay  with  various  shades  of  white,  con- 
sisting, according  to  Wedgwood,  of  60 
parts  alumina  and  40  silica.  It  probably 
268 


originated  in  the  decomposition  of  fel- 
spar. 

PORCELAIN  JASPER.  A  variety 
of  jasper,  produced  by  the  action  of  sub- 
terraneous fire  on  clay  slate. 

PORI'FERA  (poms,  a  pore,  fero,  to 
bear).  A  class  of  the  Radiata,  consisting 
of  soft,  gelatinous  animals,  which  have 
their  body  traversed  internally  by  nu- 
merous anastomozing  canals,  commencing 
from  superficial  minute  pores,  and  termi- 
nating in  large  open  vents. 

PO'RISM  (n-opto-jua,  a  corollary). 
Something  deduced  from  a  previous 
demonstration.  In  the  original  Greek 
of  Euclid's  Elements,  the  corollaries  to 
the  propositions  are  called  porisms ;  but 
this  scarcely  explains  the  nature  of  po- 
risms, as  it  is  manifest  that  they  are 
different  from  simple  deductions  from 
the  demonstrations  of  propositions.  Prof. 
Playfair  defines  a  porism  to  be  "  A  pro- 
position affirming  the  possibility  of  find- 
ing such  conditions  as  will  render  a  cer- 
tain problem  indeterminate  or  capable 
of  innumerable  solutions."  This  defi- 
nition represents  a  porism  as  almost  the 
same  as  an  indeterminate  problem.  Every 
indeterminate  problem  containing  a 
locus  may  be  made  to  assume  the  form  of 
a  porism,  but  not  the  converse.  Porisms 
are  of  a  more  general  nature  than  inde- 
terminate problems  which  involve  a 
locus. 

PORO'SITY.  That  property  of  matter, 
in  consequence  of  which  it  does  not  com- 
pletely fill  the  space  which  bodies  occupy ; 
and  this  is  owing  to  the  presence  of 
pores,  or  interstices,  which  occur  among 
the  particles  of  bodies,  even  the  densest. 
The  mass  and  density  of  bodies  are  esti- 
mated according  to  their  various  degrees 
of  porosity:  the  greater  the  mass,  the 
less  porous  will  be  the  substance ;  and, 
of  two  bodies,  that  is  the  more  dense, 
which  with  equal  bulk  contains  the 
greater  mass. 

POR'PHYRY  (7rop0i/pa,  purple).  An 
unstratified  or  igneous  rock.  This  term 
was  applied,  in  the  time  of  Pliny,  to  a 
red  rock,  with  small,  angular,  white 
bodies,  diffused  through  it,  which  are 
crystallized  felspar,  brought  from  Egypt ; 
and  hence  it  has  been  applied  to  every 
species  of  unstratified  rock  in  which 
detached  crystals  of  felspar,  or  other 
mineral,  are  diffused  through  a  base  of 
other  mineral  composition.  Thus,  clay- 
stone  with  crystals  of  felspar,  is  called 
claystone  porphyry. 

PORTLAND    LIMESTONE.      Port- 


POS 


PO  w 


land  Beds.  A  series  of  limestone  strata, 
belonging  to  the  upper  part  of  the  Oolite 
group,  found  chiefly  in  England,  in  the 
island  of  Portland,  on  the  coast  of  Dor- 
setshire. The  great  supply  of  the  build- 
ing stone  used  in  London  is  from  these 
quarries.  Portland  Sand  is  an  inter- 
mixture of  siliceous  and  calcareous  sand, 
containing  green  particles.  Portland 
Oolite  is  a  calcareo-siliceous,  more  or  less 
oolitic  freestone,  of  a  yellowish-white 
colour,  containing  nodules  of  flint  in  its 
upper  part. 

PORTU'NIDvE.  Paddling  Crabs;  a 
family  of  the  brachyurous  crustaceans, 
nearly  allied  to  the  Cancerians. 

POSITION.  An  arithmetical  rule, 
also  called  the  rule  of  Supposition,  the 
Rule  of  False,  or  the  Rule  of  Trial  and 
Error.  It  consists  in  assuming  numbers, 
and  operating  upon  them,  in  order  to 
discover  the  true  number.  Single  Posi- 
tion relates  to  those  questions  in  which 
the  results  are  proportional  to  the  sup- 
positions, and  in  which,  consequently, 
one  assumption  only  is  required.  Double 
Position  embraces  questions  in  which 
the  results  are  not  proportional  to  the 
suppositions,  and  in  which  two  assump- 
tions are  necessary  in  order  to  find  the 
true  answer. 

POSITIVE  QUANTITY.  In  Algebra, 
this  term  denotes  an  affirmative  or  addi- 
tive quantity.  Its  symbol,  +,  which  is 
read  plus,  signifies  that  the  quantity  to 
which  it  is  prefixed,  must  be  added  ;  and, 
if  no  symbol  is  prefixed,  the  quantity  is 
still  understood  to  be  positive. 

POSITIVE  TERMS.  In  Logic,  those 
terms  which  denote  a  certain  view  of  an 
object  as  being  actually  taken  of  it,  are 
called  positive.  They  are  thus  distin- 
guished from  privative  terms,  which  de- 
note that  this  view  might  be  taken  of  an 
object,  but  is  not;  and  from  negative 
terms,  which  denote  that  such  a  view  is 
not  and  could  not  be  formed  of  the  object. 
"  A  living  man"  is  an  illustration  of  the 
first  kind  of  terms  ;  "  a  lifeless  man,"  of 
the  second;  "a  lifeless  carcase,"  of  the 
third. 

POSSIBLE.  This  word,  like  the  others 
of  kindred  meaning,  relates  sometimes 
to  contingency,  sometimes  to  power; 
and  these  two  senses  are  frequently  con- 
founded. In  the  former  sense,  we  say, 
"it  is  possible  this  patient  may  recover," 
not  meaning,  that  it  depends  on  his 
choice,  but  that  we  are  not  sure  whether 
the  event  will  not  be  such.  In  the  latter 
sense  it  is  "  possible"  to  the  best  man  to 


violate  every  rule  of  morality ;  since  if  it 
were  out  of  his  power  to  act  so  if  he 
chose  it,  there  would  be  no  moral  good- 
ness in  the  case;  though  we  are  quite 
sure  that  such  will  never  be  his  choice 
( Whately).     See  Impossibility. 

POSTERIOR  MARGIN.  A  term  ap- 
plied to  that  side  of  the  bosses  of  acepha- 
lous bivalves,  which  contains  the  liga- 
ment. 

PO'STULATE  (postulatum,  a  thing 
demanded).  A  thing  required  to  be 
granted,  for  the  purpose  of  reasoning. 
The  object  of  the  postulates  in  Euclid  is 
to  declare  that  the  only  instruments,  the 
use  of  which  is  permitted  in  Geometry, 
are  the  rule  and  the  compass. 

POTASH.  Potassa.  The  hydrated 
protoxide  of  potassium,  procured  by  the 
incineration  of  vegetables,  and  named 
from  the  circumstance  that  the  water  in 
which  the  ashes  are  washed  is  evaporated 
in  iron  pots. 

POTA'SSIUM.  Kalium.  A  metallic 
substance,  white,  with  a  brilliant  lustre, 
like  mercury,  hard  and  brittle  at  32°, 
soft  and  malleable  at  50°,  fluid  at  150°, 
and  volatilized  below  a  red  heat. 

POTENTIAL  MOOD.  This  mood, 
according  to  the  views  of  Crombie  and 
Greenlaw,  is  strictly  subjunctive,  and 
in  all  those  cases  in  which  its  signifi- 
cation is  potential,  it  is  by  ellipsis, 
and  not  by  its  own  proper  power  of  ex- 
pression. 

POT-METAL.  A  mixture  of  copper 
and  about  a  fourth  its  weight  of  lead. 

POTSTONE.  Lapis  Ollaris.  A  green- 
ish-grey mineral,  occurring  in  thick  beds 
in  primitive  slate,  and  fashioned  into 
culinary  vessels  in  Greenland.  It  is  a 
sub-species  of  the  rhomboidal  mica  of 
Jameson. 

POTTER'S  CLAY.  A  variety  of  clay 
of  various  colours,  disintegrating  on  ex- 
posure to  the  air;  when  mixed  with 
sand,  it  is  made  into  bricks  and  tiles, 
and  is  also  used  for  coarse  pottery. 

POWER.  In  Mechanics,  this  term  de- 
notes any  force,  animate  or  inanimate, 
which,  being  applied  to  a  machine,  tends 
to  produce  or  to  prevent  motion ;  in  the 
former  case,  it  is  termed  a  moving  power 
or  force ;  in  the  latter,  a  sustaining  power 
or  force.     Power  is  latent  force. 

POWER  OF  NUMBERS.  In  Alge- 
bra and  Arithmetic,  any  given  number 
is  said  to  be  in  its  first  power ;  multiplied 
by  itself,  it  becomes  the  square,  or  second 
power;  this,  again,  multiplied  by  the 
original  number,  becomes  the  cube,  or 
N3 


PRE 


PRE 


third  power;  and,  by  continuing  the 
multiplications  by  the  same  original  num- 
ber, we  obtain  the  fourth,  the  fifth,  the 
sixth,  &c.  powers.  Thus  taking  the 
number  2, — 

21  =    2,  or  1"  power; 
2    x  2',  or  22  =    4,  or  2nd  power ; 

22  x  2,  or  23  =    8,  or  3rd  power  ; 

23  x  2,  or  2*  =  16,  or  4th  power ; 

24  x  2,  or  25  =  32,  or  5th  power; 

1.  When  it  is  said  that  1  is  the  square 
of  1,  there  is  a  logical  error  in  the  use 
of  the  terms :    it  ought  to  be  thus  — 

1  square  is  the  square  of  1  linear ;  thus 
1  Q  is  the  square  of  — 

2.  The  numbers  indicating  the  powers, 
are  called  the  exponents  or  indices ;  and 
it  is  evident  that  powers  of  the  same 
quantity  are  multiplied  by  adding  their 
exponents,  and  divided  by  subtracting 
their  exponents. 

3.  With  this  subject  is  connected  the 
term  dimension.  Thus,  a1,  a2,  a3,  &c. 
are  said  to  be  of  one,  two,  three,  &c.  di- 
mensions, respectively  ;  and,  in  general, 
any  product  is  said  to  be  of  n  dimensions, 
if  the  sum  of  the  indices  of  its  several 
literal  factors  is  equal  to  n.  Thus  ab, 
that  is,  a'lb*  is  of  two  dimensions ;  3  a263 
is  of  five  dimensions ;  and  so  on. 

4.  A  power  in  the  denominator  of  a 
fraction  is  also  expressed  by  placing  it  in 
the  numerator,  and  prefixing  the  nega- 
tive sign  to  its  index ;  thus 

a— *,  a~it  a—3,  a—*, 

signify-,   _,    — ,    — ,   respectively. 
a1     a2    a3    an 

These  are  called  the  negative  powers  of  a. 

PRACTICE.  An  arithmetical  rule, 
deriving  its  name  from  its  wide  practical 
application,  and  teaching  how  to  find  the 
value  of  any  number  of  articles,  having 
given  the  value  of  one ;  or  to  find  the 
value  of  any  quantity,  having  given  the 
value  of  a  single  unit. 

PRjEFLORA'TION  (prce,  before,  flo- 
reo,  to  flower).  JEslivation.  A  term  in 
Botany,  denoting  the  manner  in  which 
the  floral  envelopes  of  plants  are  ar- 
ranged previously  to  their  expansion. 

PRASE  {irpaaov,  a  leek).  A  mineral 
substance  of  a  leek-green  colour,  consist- 
ing apparently  of  an  intimate  mixture  of 
common  quartz  and  actonite,  and  found 
in  the  island  of  Bute  and  in  Borrow- 
dale. 

PRECESSION  OF  EQUINOXES. 
The  term  applied  to  the  slow  but  regular 
retro gradation  of  the  equinox  along  the 
270 


ecliptic,  from  east  to  west,  or  in  the  con- 
trary direction  to  that  in  which  the  sun 
appears  to  move  in  that  circle.  Thus,  the 
place  of  the  equinox  among  the  stars,  at 
every  subsequent  moment,  precedes  (with 
reference  to  the  diurnal  motion)  that 
which  was  held  the  moment  before.  The 
amount  of  annual  retrogradation  is  only 
50"- 10,  or  about  a  degree  in  seventy-two 
years.  The  period  in  which  the  equinox 
would  perform  a  complete  tour  of  the 
ecliptic,  is  25,868  years. 

PRECIPITATE  (prccceps,  headlong). 
A  solid  substance  precipitated,  or  thrown 
down  from  a  solution,  by  adding  a  re- 
agent. Thus  we  have  the  red  precipitate 
or  the  peroxide  of  mercury;  the  white 
precipitate,  or  the  ammoniated  chloride  ; 
the  precipitate  per  se,  or  the  purple,  &c. 

PRECIPITATION  {prceceps,  head- 
long). The  process  of  throwing  down 
solids  from  solutions  in  which  they  are 
contained.  The  substance  so  separated 
is  called  a  precipitate ;  and  the  substance 
employed  to  produce  this  effect,  a  pre- 
cipitant. This  process  is  the  opposite  to 
that  of  chemical  solution. 

PRE'DICABLE.  In  Logic,  a  term 
which  can  be  affirmatively  predicated  of 
several  others.  Predicables  are  also 
called  common  terms,  from  their  be- 
longing each  to  several  others  all 
alike. 

PRE'DICAMENT.  The  predicaments 
or  categories  of  logicians  are  certain 
general  heads,  or  summa  genera,  under 
which  all  abstract  ideas,  and  their  signs, 
common  words,  may  be  arranged.  The 
classification  of  predicaments  will  be 
found  under  the  term  Categories;  it 
was  introduced  by  Archytas,  and  adopted 
by  Aristotle. 

PRE'DICATE.  The  predicate  of  a 
proposition  is  that  term  which  is  affirmed 
or  denied  of  the  other.  Logically,  the 
predicate  occupies  the  last  place  in  a 
proposition,  though,  not  unfrequently,  it 
is  placed  first. 

PREHNITE.  A  zeolitic  substance, 
the  grass-green  variety  of  which,  found 
in  South  Africa,  has  been  mistaken  for 
chrysolite,  chrysoprase,  and  even  eme- 
rald. The  variety  which  occurs  in  small 
thin  crystals  is  called  koupholite. 

PREMISS.  In  Logic,  a  proposition 
employed  to  establish  a  certain  conclu- 
sion. The  major  premiss  is  that  in 
which  the  major  term  is  compared  with 
the  middle ;  the  minor  premiss,  that  in 
which  the  minor  term  is  compared  with 
the  middle.    The  two  premises  of  a  syl- 


PRI 


PRI 


logism  are    sometimes    called    together 
the  antecedent. 

PREPOSITION  (prcepositus,  placed 
before).  A  word  which  connects  two 
words  together,  in  such  a  manner  as  to 
indicate  the  relation  which  the  things  or 
ideas  signified  by  them  bear  to  each 
other.  The  name  of  this  part  of  speech 
has  been  derived  from  the  accidental 
circumstance  of  its  being  placed  imme- 
diately before  the  object  related  to  the 
other  thing  named ;  but  the  essence  of 
the  preposition  is,  to  signify  relative  po- 
sition. "  Every  preposition,"  says  Adam 
Smith,  "  denotes  some  relation  con- 
sidered in  concrete  with  the  correlative 
object." 

PRESSURE.  The  application  of  force 
to  a  resisting  body,  when  that  force  is  in 
continued  contact  with  the  body  on  which 
it  is  exerted.  The  centre  of  pressure  is 
that  point  at  which  the  whole  amount  of 
pressure  may  be  applied  with  the  same 
effect  as  it  has  when  distributed. 

PRIMARY.  A  term  applied,  in  the 
astronomical  division  of  the  sphere,  to 
the  great  circle  traced  upon  its  surface, 
half  way  between  the  poles.  All  the 
smaller  circles,  which  intervene  between 
the  primary  and  the  poles,  are  called 
parallels. 

PRIMARY  LIMESTONE.  A  modi- 
fication of  limestone,  with  a  crystalline 
texture,  occurring  under  many  different 
aspects,  and  in  every  member  of  the 
series,  so  that  no  particular  position  can 
be  ascribed  to  it.  Its  colours  are 
various. 

PRIMARY  ROCKS.  The  lowest  se- 
ries of  the  stratified  rocks,  characterized 
by  a  crystalline  texture,  and  by  the  ab- 
sence of  organic  remains.  This  term 
has  no  reference  to  priority  of  formation, 
but  expresses  the  order  of  their  occur- 
rence, they  being  the  first  after  granite. 
These  rocks  were  termed  by  Mr.  Lyell 
metamorphic,  from  the  supposition  that 
they  were  deposited  in  a  sedimentary 
form,  and  were  afterwards  altered  by  the 
action  of  heat. 

PRIME    NUMBER.      Any    number 

which  cannot  be  separated  into  factors, 

X  f*  as  7',  11,  13,  17,  &c,  is   called   a  prime 

f '  f    '  number.     Every  number  which  can  be 

so  separated,  as  6,  8,  9,  12,  &c,  is  called 

a  composite  number.  When  two  numbers 

have  no  common    measure  but    unity, 

they  are  said  to  be  prime  to  each  other  : 

thus  3  is  prime  to  7  ;  13  to  31  ;  and  so 

on.     A  prime   number  is   one    which  is 

prime  to  every  other  number. 

271 


PRIMINE  {primus,  first).  The  first 
or  outermost  sac  of  the  ovule  in  plants. 

PRIMITIVE  WORDS.  In  grammar, 
these  are  words  not  derived  from  any 
other  word  in  the  language,  as  school. 
See  Derivative  Words. 

PRIMULA'CEjE.  The  Primrose  tribe 
of  dicotyledonous  plants,  peculiarly  dis- 
tinguished by  the  stamens  being  oppo- 
site to  the  lobes  of  the  gamopetalous 
corolla,  and  by  having  a  superior  capsule 
with  a  free  central  placenta. 

PRIMUM  MOBILE.  A  term  given 
by  the  old  astronomers  to  an  imaginary 
sphere,  by  the  motion  of  which  diurnal 
motion  was  given  to  the  heavens. 

PRINCE'S  METAL.  Prince  Rupert's 
Metal.  A  species  of  copper  alloy,  in 
which  the  proportion  of  zinc  is  greater 
than  in  brass. 

PRISM  {irpiafxa,  from  Trpt'co,  to  saw). 
A  prism  is  defined,  in  Geometry,  to  be  a 
solid  figure  contained  by  plane  figures, 
of  which  two  that  are  opposite  are  equal, 
similar,  and  parallel  to  one  another,  and 
the  others  parallelograms.  The  name  is 
derived  from  the  property  exhibited  by 
the  glass  prism  of  separating  a  ray  of 
light  into  its  constituent  parts. 

Prism,  Achromatic.  A  prism  through 
which  objects  are  viewed  refracted  in- 
deed, so  that  they  are  not  seen  in  their 
true  position,  but  yet  free  from  a  prisma- 
tic fringe  about  their  edges.  It  con- 
sists of  two  prisms  fitted  together,  the 
one  being  of  flint,  the  other  of  crown- 
glass.  The  vertical  angle  of  the  flint- 
glass  prism  must  be  less  than  that  of  the 
crown-glass,  and  their  sizes  must  be  in- 
versely as  their  dispersive  powers.  In 
English  flint-glass  the  vertical  angle  of 
the  flint-glass  prism  must  be  §  that  of 
the  crown-glass,  but  in  Fraunhofer's  it 
must  be  £  the  size. 

PRISMATIC  CRYSTALS.  The  square 
prism  differs  from  the  cube  only  in  having 
its  lateral  edges  either  longer  or  shorter 
than  the  terminal.  The  right  rhombic 
prism  is  a  right  prism  whose  base  is  a 
rhomb.  The  oblique  rhombic  prism  differs 
from  the  preceding  in  being  oblique  in 
the  direction  of  one  of  the  diagonals  of 
the  base.  All  other  prismatic  crystals, 
which  do  not  possess  any  of  the  degrees 
of  symmetry  which  characterize  the 
other  prisms,  are  comprehended  in  the 
class  of  doubly  oblique  prisms.  In  all 
the  varieties  of  prisms,  the  crystals 
are  supposed  to  rest  on  one  of  the  bases 
or  terminal  planes  of  the  prism,  the  sur- 
faces which  bound  the  prism  lengthwise 
N4 


PRO 


PRO 


being  called  lateral  planes.  The  edges 
at  which  these  meet  are  lateral  edges  ; 
and  the  edges  at  which  they  meet  the 
terminal  planes  are  terminal  edges. 

PRISMATIC  SPECTRUM.  Solar 
Spectrum.  The  variously-coloured  ap- 
pearance presented  by  a  ray  of  light, 
when  separated  into  its  constituent  parts 
by  refraction  through  a  glass  prism. 
The  appearance  consists  of  an  oblong 
image,  containing  seven  colours,  which 
are  simple  or  homogeneous,  as  distin- 
guished from  the  white  ray,  which  is 
compound  or  heterogeneous. 

PRISME'NCHYMA  (npiana,  a  prism, 
2yxwm<*.  infusion).  The  name  given  by 
Morren  to  the  prismatical  variety  of  the 
parenchyma  of  plants. 

PRIVATIVE  TERMS.  In  Logic, 
terms  which  denote  that  a  certain  view 
might  be  taken  of  an  object,  though  it  is 
not  so  taken,  are  called  privative.  Thus, 
in  the  expression,  "the  moon  is  some- 
times invisible,"  the  word  invisible  is 
used  privatively,  for  the  moon  is  capable 
of  being  seen.     See  Negative  Term. 

PROBABILITIES  or  CHANCES.  The 
popular  use  of  these  terms  has  no  very 
distinct  meaning.  The  mathematical 
meaning  points  out  a  real  value  existing 
in  the  circumstances.  A  question  of 
probability  is  termed  direct,  when,  cer- 
tain causes  being  given  as  existent,  from 
which  a  certain  event  may  proceed,  the 
probability  of  that  event  happening  is 
required.  A  question  of  probability  is 
termed  inverse,  when,  an  event  being 
given  as  existent,  and  proceeding  from 
one  of  several  causes,  the  probability  of 
one  proposed  cause  being  the  true  one 
is  required. 

PROBLEM  (irpoflKn/jia,  any  thing  pro- 
posed as  a  task).  A  proposition  in  which 
something  is  proposed  to  be  done ;  as  a 
line  to  be  drawn  under  some  given  con- 
ditions, some  figure  to  be  constructed, 
&c.  The  solution  of  the  problem  con- 
sists in  showing  how  the  thing  required 
may  be  done  by  the  aid  of  the  rule  and 
the  compass.  The  demonstration  con- 
sists in  proving  that  the  proceos  indi- 
cated in  the  solution  really  attains  the 
required  end.  A  postulate  is  a  problem, 
the  solution  of  which  is  assumed. 

PROBOSCI'DEA.  A  group  of  pachy- 
dermatous animals,  containing  only  the 
elephant  and  its  extinct  congeners,  the 
mammoth  and  the  mastodon,  character- 
ized by  their  elongated  nose,  or  pro- 
boscis. 

PROCYON,  or  a  CANIS  MINOR.  A 
272 


star  of  the  first  magnitude  in  the  con- 
stellation Canis  Minor. 

PRODUCT.  In  arithmetic,  a  product 
is  the  result  of  the  multiplication  of  two 
or  more  quantities.  The  result  of  the 
addition  of  two  or  more  quantities  is 
called  the  sum. 

PRODUCTA.  An  extinct  genus  of 
fossil  bivalve  shells,  occurring  only  in 
the  older  secondary  rocks.  It  is  closely 
allied  to  the  living  genus  Terebratula. 

PROGRESSION  {progredior,  to  ad- 
vance). This  term,  in  its  general  sense, 
means  going  forward ;  but  its  use  in 
algebra  and  arithmetic  denotes  that  the 
progress  takes  place  in  a  determinate 
order — that  it  is  motion  measured  by 
some  scale. 

1.  Progression,  Arithmetical.  Quan- 
tities are  said  to  be  in  arithmetical  pro- 
gression, when  they  increase  or  decrease 
by  a  common  difference.  Thus,  1,  3,  5, 
7,  &c,  8,  4,  0,  —4,  &c. ;  a,  a  +  d,  a  +  2d, 
a  +  3d,  &c,  are  in  arithmetical  progres- 
sion, the  common  differences  being  2, 
— 4,  and  d,  respectively. 

2.  Progression,  Geometrical.  Quantities 
are  said  to  be  in  geometrical  progression, 
when  they  increase  or  decrease  by  a 
common  factor;  in  other  words,  when 
the  ratio  of  any  two  successive  terms  is 
the  same.  Thus,  1,  3,  9,  27,  &c,  16,  4, 
1.  h  &c,  J,  HSs.  — 4i  —5%  &c-,  a,  ar, 
ar*,  ar3,  &c,  are  in  geometrical  progres- 
sion, the  common  factors,  or  ratios  (as 
they  are  called),  being  3,  £,  — f,  and  r, 
respectively. 

3.  Progression,  Harmonical.  Quantities 
are  said  to  be  in  harmonical  progression, 
when  their  reciprocals  are  in  arithmetical 
progression ;  in  other  words,  when  any 
three  successive  terms  are  so  related, 
that  the  first  is  to  the  third  as  the  dif- 
ference between  the  first  and  the  second 
is  to  the  difference  between  the  second 
and  the  third.  Thus,  since,  1,  3,  5,  7, 
&c,  £,  — £,  — |,  —  |,  are  in  arithmetical 
progression,  their  reciprocals,  1,  J,  £, 
\,  &c,  4,  -—4,  — §,  — §,  &c,  are  in  har- 
monical progression.  Again,  if  a,  b,  ct 
are  in  harmonical  progression, 

a  \  c  \\  a  —  b  \  b  —  c. 

PROJECTILE  (projicio,  to  cast  for- 
ward). A  heavy  body  which  has  been 
projected  in  a  direction  not  vertical.  The 
theory  of  projectiles  investigates  the  rela- 
tions between  the  space  described,  the 
time  of  motion,  and  the  velocity  acquired 
by  a  body  when  impelled  by  some  motive 
force. 

PROJECTION.     The  representation 


PRO 


PRO 


of  the  surface  of  a  sphere  on  a  plane, 
according  to  the  laws  of  perspective.  In 
projecting  a  spherical  surface  on  a  plane, 
some  parts  must  be  unduly  contracted 
or  enlarged  in  proportion  to  others.  The 
projections  chiefly  used  in  maps  are  the 
orthographic,  the  stereographic,  and 
Mercator's. 

1.  In  the  Orthographic  projection,  every 
point  of  the  hemisphere  is  referred  to  its 
diametral  plane  or  base,  by  a  perpendi- 
cular let  fall  on  it ;  so  that  the  represen- 
tation of  the  hemisphere  thus  mapped  on 
its  base,  is  such  as  it  would  appear  to  an 
eye  placed  at  an  infinite  distance  from 
it.  In  this  projection,  only  the  central 
portions  are  represented  of  their  true 
forms,  while  all  the  exterior  is  more  and 
more  distorted  and  crowded  together  as 
we  approach  the  edges  of  the  map. 
Owing  to  this  cause,  the  orthographic 
projection,  though  very  good  for  small 
portions  of  the  globe,  is  of  little  service 
for  large  portions. 

2.  The  Stereographic  projection  is  in 
great  measure  free  from  this  defect. 
The  eye  is  supposed  to  be  placed  at  the 
surface  of  the  sphere,  and  to  view  the 
concave  of  the  opposite  hemisphere 
through  the  plane  of  that  circle,  in  the 
pole  of  which  the  eye  is  placed.  Hence, 
the  position  on  this  plane  of  any  point 
of  the  spherical  surface  will  be  indicated 
by  a  line  drawn  from  that  point  through 
the  plane  to  the  eye.  This  is  a  true 
perspective  representation :  all  circles 
on  the  sphere  are  represented  by  circles 
in  the  projection ;  every  very  small  tri- 
angle on  the  sphere  is  represented  by  a 
similar  triangle  in  the  projection.  This 
and  the  preceding  mode  of  projection 
may  be  considered  natural,  inasmuch  as 
they  are  really  perspective  representa- 
tions of  the  surface  on  a  plane. 

3.  Mercator's  projection  is  entirely 
artificial,  representing  the  sphere  as  it 
cannot  be  seen  from  any  one  point,  but 
as  it  might  be  seen  by  an  eye  carried 
successively  over  every  part  of  it.  In  it, 
the  degrees  of  latitude,  and  those  of 
longitude,  bear  always  to  each  other  their 
due  proportion  ;  the  equator  is  conceived 
to  be  extended  out  into  a  straight  line, 
and  the  meridians  are  straight  lines  at 
right  angles  to  it.  Like  the  stereo- 
graphic projection,  it  gives  a  true  repre- 
sentation, as  to  form,  of  every  particular 
small  part,  but  varies  greatly  in  point  of 
scale  in  its  different  regions;  the  polar 
portions  in  particular  being  extrava- 
gantly enlarged,  and   the  whole   map, 

273 


even  of  a  single  hemisphere,  not  being 
comprisable  within  any  finite  limits. 

4.  In  the  Gnomonic  or  Central  projec- 
tion, the  eye  is  supposed  to  be  placed  in 
the  centre  of  the  sphere,  and  the  various 
objects  to  be  delineated  are  transferred 
from  the  sphere  to  a  plane,  which  is  a 
tangent  to  its  surface.  The  entire  hemi- 
sphere can  never  be  represented  by  this 
projection,  since  the  circumference  which 
terminates  it  is  on  a  level  with  the  eye, 
and  is  therefore  parallel  to  the  plane  of 
projection.  In  this  case,  the  parallels  of 
latitude  will  be  concentric  circles,  and 
the  meridians  straight  lines  radiating 
from  the  centre.  This  method  is  chiefly 
employed  in  dialling,  and  derives  its 
name  from  the  connexion  between  the 
methods  of  describing  it  and  those  for 
the  construction  of  a  gnomon  or  dial. 

5.  Projection  by  Development.  By  this 
expression  is  understood  the  unfolding 
or  spreading  out  of  the  spherical  surface 
on  a  plane.  As  a  preparatory  step,  how- 
ever, the  sphere  must  be  converted  into 
a  cone  or  a  cylinder,  inasmuch  as  por- 
tions of  these  forms  most  resemble 
portions  of  a  sphere,  and  the  forms 
themselves  are  susceptible  of  the  re- 
quired development. 

PROLEGS.  The  wart-like  tubercles 
which  represent  legs  on  the  hinder  seg- 
ment of  caterpillars. 

PROLI'FEROUS  {proles,  offspring, 
fero,  to  bear).  A  term  applied  in  botany 
to  a  flower  which  produces  another  flower 
from  its  centre,  as  in  certain  roses. 

PROMERO'PIDiE.  The  Hoopoes;  a 
family  of  the  Insessores,  or  Perching 
birds,  one  species  of  which,  the  upupa 
epops,  occasionally  visits  Europe.  See 
Tenuirostres. 

PROOF  AND  INFERENCE.  In 
addition  to  what  has  been  adduced  under 
the  article,  Inference  and  Proof,  the 
learned  author  of  the  "  Elements  of 
Logic"  observes,  that  proving  may  be 
defined  "the  assigning  of  a  reason  or 
argument  for  the  support  of  a  given  pro- 
position;" and  Inferring,  "the  deduc- 
tion of  a  conclusion  from  given  premises." 
In  the  one  case  our  conclusion  is  given, 
and  we  have  to  seek  for  arguments ;  in 
the  other,  our  premises  are  given,  and  we 
have  to  seek  for  a  conclusion.  He  adds, 
that  "proving"  may  be  compared  to  the 
act  of  putting  away  any  article  into  the 
proper  receptacle  of  goods  of  that  de- 
scription ;  "  inferring,"  to  that  of  bringing 
out  the  article  when  needed. 

PROPA'GO;  PROPA'GULUM.  The 
N5 


PRO 


PRO 


former  of  these  terms  was  applied  by  the 
older  botanists  to  the  branch  laid  down 
in  the  process  of  layering.  The  latter 
denotes  an  offset  in  certain  plants. 

PROPERTIES  OF  BODIES.  The 
physical  properties  are  divided  into  the 
essential,  or  principal ;  viz.  extension  and 
impenetrability,  which  are  common  to 
all  bodies,  and  indispensable  to  their  ex- 
istence ;  and  the  non-  essential,  or  acces- 
sory, as  compressibility,  expansibility, 
porosity,  divisibility,  elasticity,  and  gra- 
vity. 

PROPERTY.  In  Logic,  this  term 
denotes  a  predicable  which  expresses 
something  essentially  conjoined  to  the 
essence  of  the  species.  It  is  thus  dis- 
tinguished from  the  logical  accident, 
which  denotes  something  contingently 
joined  to  the  essence.  Thus,  redness  is 
a  property  of  blood,  but  an  accident  of  a 
house. 

PROPORTION.  This  term  denotes 
the  portions,  or  parts,  of  one  magnitude 
which  are  contained  in  another.  In  the 
language  of  Mathematics,  the  term  has 
been  appropriated  to  express  the  equality 
of  ratios ;  or,  as  it  may  be  less  minutely 
explained,  the  case  in  which  one  magni- 
tude is  as  many  times  greater  or  less 
than  another,  as  a  third  magnitude  is 
greater  or  less  than  a  fourth.    See  Ratio. 

PROPOSITION  {propono,  to  propose). 
A  short  discourse,  in  which  a  geometrical 
truth  is  stated  and  considered  •,  it  being 
thereby  proposed  either  to  demonstrate 
something  which  is  asserted,  in  which 
case  the  proposition  is  called  a  theorem ; 
or  to  show  the  manner  of  doing  some- 
thing which  is  required  to  be  done,  in 
which  case  the  proposition  is  called  a 
problem. 

A  logical  proposition  is  "a  sentence 
indicative;"  in  other  words,  a  sentence 
which  affirms  or  denies.  A  proposition 
is  distinguished,  with  reference  to  its 
substance,  as  categorical,  when  it  ex- 
presses anything  absolutely,  as  "  Caesar 
deserved  death ;"  hypothetical,  when  it 
expresses  any  thing  under  a  hypothesis, 
as,  "  If  Caesar  was  a  tyrant,  he  deserved 
death."  Categorical  propositions  are 
termed  pure,  when  they  assert  simply  or 
purely,  that  the  subject  does  or  does  not 
agree  with  the  predicate  ;  and  modal, 
when  they  denote  in  what  mode  or  man- 
ner it  agrees.  Thus,  "  Brutus  killed 
Caesar,"  is  a  pure  categorical  proposition ; 
while,  "  Brutus  killed  Caesar  justly,"  is 
modal. 

PROSE'NCHYMA.  A  term  applied 
274 


by  Link  to  that  form  of  parenchyma  in 
plants,  in  which  the  cells  taper  to  each 
end,  and  overlap  each  other;  the  term 
parenchyma  being  restricted  to  that  form 
of  the  tissue,  in  which  the  cells  have 
truncated  extremities. 

PROTEIN  (Trpcoxeuo),  to  hold  the  first 
place).  The  name  given  by  Mulder  to 
the  precipitate  obtained  by  adding  acetic 
acid  to  a  solution  of  caustic  potash,  con- 
taining fibrin,  albumen  or  gelatine,  ani- 
mal or  vegetable,  in  solution. 

PRO'TEOLITE.  Under  this  term  and 
that  of  Cornubianite,  Dr.  Boase  describes 
the  rock  in  contact  with  granite,  which 
has  been  called  argillaceous  schist,  or 
clay-slate,  greywacke,  or  killas.  The 
proteolite  is  of  a  lighter  colour  than  the 
cornubianite,  soft,  arenaceous,  and  slaty. 
They  appear  to  be  chiefly  composed  of 
compact  felspar,  with  quartz,  mica,  and 
schorl,  and  contain  beds  of  that  sub- 
stance and  of  quartz. 

PROTHO'RAX.  The  first  of  the 
three  segments  which  constitute  the 
thorax  in  insects. 

PROTO-  (ttpwtop,  the  first).  This  pre- 
fix denotes,  in  Chemistry,  the  lowest  de- 
gree in  which  one  body  unites  with  an- 
other, as  prot-ox.ide.  Per  denotes  the 
highest  degree,  as  per-oxide. 

PRO'TOGENE.  Talcose  Granite.  A 
mixture  of  felspar,  quartz,  and  talc  or 
chlorite.  It  occurs  abundantly  in  the 
Alps  of  Savoy,  and  is  found  in  Cornwall, 
where,  on  decomposition,  it  yields  the 
china-clay  or  porcelain-earth,  which  is 
annually  exported  in  large  quantities. 

PROTOZO'A  (wpwrov,  first,  £5>ov,  an 
animal).  A  designation  of  one  of  the 
primary  divisions  of  the  Animal  King- 
dom, from  their  constituting  the  first 
step  of  animal  organization.  They  cor- 
respond with  the  Acrita  of  Macleay,  with 
the  Cryptoneura  of  Rudolphi,  and  with 
the  Oozoa  of  other  witers. 

PROTOZO'IC  SYSTEM  (ttpwtov,  first, 
£wov,  an  animal).  A  geological  term,  ap- 
plied to  the  lowest  system  of  rocks  in 
which  the  traces  of  any  organic  structure 
have  been  discovered.  It  is  the  system 
next  in  ascending  order  to  the  hypozoic. 

PROXIMATE  PRINCIPLE.  A  term 
applied,  in  analyzing  any  body,  to  the 
principle  which  is  nearest  to  the  natural 
constitution  of  the  body,  and  more  im- 
mediately the  object  of  sense,  as  distin- 
guished from  intermediate  or  ultimate 
principles.  Ultimate  principles  are  the 
elements  of  which  proximate  principles 
are  composed. 


PSI 


PTO 


PRCXIMUM  GENUS.  In  Logic,  the 
nearest  or  least  remote  genus  to  which  a 
species  can  be  referred.     See  Genus. 

PRUSSIAN  BLUE.  Berlin  Blue. 
The  sesqui- ferrocyanide  of  iron  ;  a  beau- 
tiful deep  blue  powder,  used  in  the 
arts. 

PRUSSIAS.  A  prussiate ;  a  name  now 
exploded,  except  in  commerce,  when  it 
denotes  a  cyanide :  what  is  termed  the 
yellow  prussiate  of  potash,  is  a  ferro- 
cyanide of  potassium. 

PRUSSIC  ACID.  A  designation  of 
hydrocyanic  acid,  from  its  being  an  in- 
gredient in  Prussian  blue. 

PRYING  and  LIFTING.  In  the 
common  use  of  a  lever  of  the  first  kind, 
the  force  is  gained  by  bearing  down  the 
long  arm  of  the  lever,  which  is  called 
prying.  In  the  second  kind  the  force  is 
gained  by  carrying  the  long  arm  in  a 
contrary  direction,  or  upward,  and  this 
is  called  lifting. 

PSEUDO-BULB.  A  term  applied  to 
the  enlarged  aerial  stem  of  orchidaceous 
plants.     It  resembles  a  tuber. 

PSEU'DO-LITE.  A  mineral  having  a 
close  affinity  to  the  pseudomorphous 
crystals  of  steatite. 

PSEUDOMALACHITE.  Prismatic 
phosphate  of  copper,  from  Rheinbreiten- 
bach,  where  it  occurs  with  quartz  which 
sometimes  passes  into  chalcedony. 

PSEUDO-MORPHOUS  {favdht,  false. 
/uop0»7,  form).  A  term  applied  to  sub- 
stances which,  not  possessing  a  crystal- 
line structure,  are  found  in  the  form  of 
regular  crystals.  These  accidental  forma- 
tions must  be  considered  as  merely  casts 
of  the  crystals  they  represent. 

PSEUDO-STRATA.  A  term  proposed 
by  Macculloch  for  those  extended  plates 
of  rocks,  not  divided  into  parallel  la- 
minae, and  commonly  called  table-layers. 
Some  geologists  make  a  distinction  be- 
tween a  stratum  and  a  bed,  meaning  by 
the  latter  what  is  called  by  Macculloch  a 
pseudo-stratum. 

PSEUDO-ZOA'RIA.  A  term  proposed 
by  Blainville  to  include  vegetables,  many 
of  which  have  been  ranked  with  the 
Polypiaria.  They  are  subdivided  into 
two  classes,  viz.  Calciphyta,  principally 
composed  of  the  genus  Corallina,  and 
Nematophyta,  including  byssus,  con- 
ferva, oscillatoria,  &c. 

PSILOMELANE.  An  ore  of  manga- 
nese containing  a  considerable  quantity 
of  barytes,  occurring  in  Devonshire, 
Cornwall,  in  the  Hartz,  and  most  manga- 
nese mines. 
275 


PSITTA'CIDjE  (psittacus,  the  parrot). 
The  Parrot  tribe;  a  family  of  birds, 
generally  referred  to  the  Scansores,  or 
Climbers,  with  which,  however,  they 
correspond  in  little  else  than  the  struc- 
ture of  the  foot,  and  this  is  adapted  rather 
for  grasping  than  for  climbing. 

PSY'CHICAL  Wvxikos,  pertaining  to 
the  psyche,  or  soul).  Relating  to  the 
phenomena  of  the  soul,  and  to  analogous 
phenomena  in  the  lower  animals.  Psy- 
chology, literally,  the  doctrine  of  the 
soul,  denotes  a  description  of  the  intel- 
lectual and  moral  faculties. 

PSYCHRO'METER  Ouxpor,  cold, 
fierpov,  a  measure).  An  instrument  for 
measuring  degrees  of  cold.  Its  action  is 
the  same  as  that  of  the  hygrometer,  and 
depends  on  the  combination  of  heat 
which  accompanies  the  evaporation  of  a 
fluid,  and  the  consequent  deposition  of 
the  vapour  contained  in  the  atmosphere. 

PTERODA'CTYL  (nrepov,  a  wing, 
daKTvXos,  a  finger).  Wing-fingered;  the 
name  of  an  extinct  genus  of  flying  rep- 
tiles, species  of  which  have  been  found 
in  the  Oolite  and  Muschelkalk.  Some 
of  the  finger  joints  are  lengthened,  so  as 
to  serve  as  the  expansors  of  a  membran- 
ous wing. 

PTEROPFNjE.  The  single  family  of 
the  frugivorous  or  omnivorous  Cheiro- 
ptera, of  which  the  pteropus  Javanicus 
may  be  considered  the  type.  They 
abound  in  warm  climates,  and  include 
some  of  the  largest  species  of  the  order. 

PTERO'PODA  (tttcpov,  a  wing,  ttovp, 
a  foot).  The  tenth  class  of  the  Mollusca, 
consisting  of  small,  soft,  floating,  marine 
animals,  which  swim  by  the  contractions 
of  two  lateral  musculocutaneous  fins, 
but  are  unable  to  fix  themselves  or  creep 
in  the  sea,  from  the  want  of  feet,  as  the 
clio,  cleodora,  &c. 

PTERY'GIANS  (wi-cpuf,  a  wing).  A 
name  given  by  Latreille  to  a  group  of  the 
Mollusca,  corresponding  to  the  cepha- 
lopods  and  pteropods  of  Cuvier,  both  of 
which  have  locomotive  organs,  consisting 
of  wing-like  expansions  of  the  skin. 

PTOLEMA'IC  SYSTEM.  A  system 
of  astronomy  so  named  from  the  famous 
geographer  Claudius  Ptolemaeus,  who 
flourished  in  Egypt  during  the  reigns  of 
the  Roman  emperors  Hadrian  and  Anto- 
ninus Pius.  He  taught  that  the  earth 
was  at  rest  in  the  centre  of  the  universe, 
and  that  the  heavens  revolved  round  it, 
from  east  to  west,  in  twenty-four  hours, 
carrying  all  the  heavenly  bodies  with 
them.  This  system  was  believed,  and 
N6 


P  UM 


PUR 


enjoyed    an   undisputed    celebrity,    for 
1400  years. 

PUBE'SCENCE  (pubesco,  to  begin  to 
have  a  beard).  The  down  of  plants,  con- 
sisting of  soft  short  hairs,  which  partially 
cover  the  cuticle,  as  in  geranium  molle. 
Also,  the  soft  hairy  down  of  insects. 

PUDDING-STONE.  Conglomerate. 
Rounded  water-worn  fragments  of  rocks 
or  pebbles,  cemented  together  by  another 
mineral  substance,  which  may  be  of  a 
siliceous,  calcareous,  or  argillaceous 
nature. 

PULLEY.  One  of  the  mechanical 
powers,  consisting,  in  its  simplest  form, 
of  a  wheel,  capable  of  turning  about  its 
axis,  which  may  be  either  fixed  or  move- 
able. A  cord  passes  over  a  portion  of 
the  circumference  ;  if  the  axis  of  the 
pulley  is  fixed,  its  only  effect  is  to  change 
the  direction  of  the  force  exerted  by  the 
cord ;  but  if  it  is  moveable,  a  mechanical 
advantage  may  be  gained.  Combinations 
of  pulleys  may  be  made  in  endless 
variety. 

PULMOBRANCHIA'TA  {pulmo,  the 
lungs,  branchice,  gills).  Pulmonia.  An 
order  of  terrestrial  Gasteropods,  named 
from  the  resemblance  between  their 
mode  of  breathing  and  that  of  animals 
possessed  of  proper  lungs.  The  snail, 
for  instance,  breaths  air,  which  is  alter- 
nately drawn  into  and  expelled  from  a 
cavity  lined  with  a  vascular  network. 
Many  of  these  animals  have  no  shell. 

PULMONA'TA  (pulmo,  the  lungs). 
An  order  of  the  Arachnida,  comprising 
those  species  which  breathe  by  means  of 
pulmonary  sacs.     See  Tracheata. 

PULMONI'GRAD  A  (;wJ»io,  the  lungs, 
gradior,  to  advance).  An  order  of  the 
Acalephce,  so  named  from  the  contrac- 
tions and  dilatations  of  their  umbrella- 
shaped  disc,  by  means  of  which  they 
move,  having  some  resemblance  to  the 
motion  of  the  lungs  in  respiration. 

PUMICE  {pumex).  A  light  spongy 
lava,  chiefly  felspathic,  of  a  white  ap- 
pearance, produced  by  gases  or  watery 
vapour  gaining  access  to  the  particular 
kind  of  glassy  lava  called  obsidian,  when 
in  a  state  of  fusion.  It  may  be  called 
the  froth  of  melted  volcanic  glass.  On 
account  of  its  fibrous  and  vesicular  state, 
it  is  so  light  as  to  float  on  water. 

PUMP.  A  machine  formed  on  the 
model  of  a  syringe,  for  raising  water  from 
various  depths  to  the  surface  of  the  earth. 
1.  In  the  common  suction  pump,  the  water 
is  pressed  into  the  pump-barrel  by  the 
atmosphere,  and  thrown  out  by  lifting. 
276 


2.  In  the  lifting  pump,  the  piston  is 
situated  in  the  lower  part  of  the  barrel, 
and  raises  the  water  through  the  whole 
distance,  by  forcing  it  upward,  without 
the    agency    of     atmospheric    pressure. 

3.  The  forcing  pump  differs  from  both 
these,  in  having  its  piston  solid,  or  with- 
out a  valve,  and  also  in  having  a  side 
pipe,  through  which  the  water  is  forced, 
instead  of  rising  in  a  perpendicular  direc- 
tion, as  in  the  others. 

Chain  pump. — This  kind  of  pump  is 
used  on  board  of  ships,  and  consists  of 
an  endless  chain  moving  over  a  wheel  on 
the  deck,  which  is  turned  round  by 
winches,  and  over  a  roller  in  the  pump- 
well,  having  saucers  or  flat  circular  pis- 
tons at  certain  intervals.  Chain  pumps, 
in  large  ships,  throw  out  a  ton  of  water 
per  minute. 

PULSE  GLASS.  A  tube  of  glass, 
having  a  bore  of  about  two  lines  in  dia- 
meter, but  at  right  angles  at  each  end, 
where  it  is  expanded  into  two  bulbs  of 
about  l£  inch  in  diameter.  The  instru- 
ment contains  water  or  spirits  of  wine, 
the  remaining  space  being  a  vacuum  :  if 
one  bulb  be  grasped  in  the  hand,  the 
liquid  will  boil  violently  in  the  other, 
owing  to  the  atmospheric  pressure  being 
removed  from  the  surface  of  the  liquid. 

PUPA.  A  term  literally  denoting  a 
baby  wrapped  up  in  swaddling  bands, 
and  applied  to  the  chrysalis,  or  nymph, 
or  second  state  of  insect  existence,  in 
which,  the  last  skin  of  the  larva  being 
thrown  off,  the  animal  appears  in  a  dif- 
ferent form,  enveloped  in  an  oblong  case, 
without  external  limbs,  and  almost  in- 
capable of  the  slightest  motion.  See 
Imago. 

PUPI'PAROUS  {pupa,  and  pario,  to 
produce).  A  designation  of  Dipterous 
insects,  which  bring  forth  their  young  in 
the  pupa  state.  They  comprise  two 
families,  known  by  the  names  of  forest- 
flies  and  bat-lice. 

PURBECK  LIMESTONE.  Purbeck 
Beds.  Limestone  strata,  belonging  to 
the  Wealden  Group,  which  intervenes 
between  the  Greensand  and  the  Oolite. 
It  is  composed  of  fresh-water  shells 
united  by  a  calcareous  cement.  It  is 
slaty,  argillaceous,  of  a  brownish  colour, 
alternating  with  slaty  marl,  and  some- 
times containing  beds  of  compact  lime- 
stone. 

PURPLE  OF  CASSIUS.  A  purple- 
coloured  powder,  precipitated  when  pro- 
tochloride  of  tin  is  added  to  a  dilute 
solution  of  gold. 


PYR 


PYR 


PURPURIC  ACID.  An  acid  obtained 
from  uric  or  lithic  acid,  remarkable  for 
its  tendency  to  form  red  or  purple  coloured 
salts  with  alkaline  bases.  Its  salts  are 
called  purpurates. 

PURPURI'N^E.  A  sub-family  of  the 
Muricidce,  named  from  the  typical  genus 
Purpura,  including  shells  whose  general 
form  resembles  that  of  the  whelks. 

PUTA'MEN  (puto,  to  prune).  A  syn- 
onymous term  for  the  endocarp,  or 
innermost  layer  of  the  pericarp  of  osseous 
fruits. 

PUTREFA'CTION.  The  spontaneous 
decomposition  of  animal  or  vegetable 
matters,  attended  with  fcetor ;  a  species 
of  fermentation. 

PUZZOLA'NO.  A  substance  of  vol- 
canic origin,  composed  principally  of 
pumice,  of  which  a  stratum  is  excavated 
in  the  neighbourhood  of  Pozzuoli,  near 
Naples.  The  mortar  which  it  makes 
with  lime  is  called  Roman  cement. 

PYCNITE  (Trevor,  thick).  A  sub- 
stance formerly  considered  as  a  variety 
of  beryl,  but  now  referred  to  topaz. 

PY'RAMID.  A  solid  figure,  contained 
by  planes  which  are  constituted  betwixt 
one  plane  and  one  point  above  it  in 
which  they  meet.  It  differs  from  a  cone, 
in  having  for  its  base  a  right-lined,  in- 
stead of  a  circular  figure.  (See  Cone). 
The  ancients  derived  the  term  nvpa/nh 
or  pyramid,  sometimes  from  nvp,  fire,  be- 
cause of  its  pointed  shape ;  sometimes 
from  nvpds,  as  if  the  pyramids  had  been 
granaries !  No  doubt  the  word,  as  well 
as  the  thing,  is  Egyptian. 

PYRITES  (ttDp,  fire).  A  compound 
of  sulphur  and  iron,  usually  occurring  in 
yellow  shining  crystals  like  brass,  and  in 
almost  every  rock,  stratified  and  unstra- 
tified.  The  shining  metallic  bodies  fre- 
quently seen  in  common  roofing-slate 
afford  a  familiar  example  of  the  mineral. 
The  term  originally  denoted  a  fire-stone, 
a  sort  of  stone  out  of  which  fire  could  be 
struck ;  because,  under  particular  circum- 
stances, the  stone  produces  spontaneous 
heat,  and  even  inflammation. 

PYRO-  (7rup,  fire).  Words  compounded 
with  this  term  denote  some  change  pro- 
duced by  the  action  of  fire : — 

1.  Pyr-acid.  An  acid  produced  by  the 
destructive  distillation  of  an  organic  acid, 
as  the  pt/ro-citric,  produced  by  decompo- 
sition of  the  citric  by  fire. 

2.  Pyr-allolite.  A  silicate  of  magnesia; 
a  mineral  belonging  to  the  talc  family, 
found  in  a  lime-quarry  in  Finland.  Its 
name  is  derived  from  its  singular  pro- 

277 


perty  of  blackening  before  the  blowpipe 
at  a  low-red  heat,  and  afterwards  becom- 
ing white  at  a  higher  temperature. 

3.  Pyr-argillite.  A  silicate  of  alumina 
and  other  matters,  found  in  granite  in 
Finland,  emitting  an  argillaceous  odour 
when  heated. 

4.  Pyro-chlore.  A  new  mineral  found 
in  Norway,  in  zircon-syenite.  It  is  so 
called  because  it  becomes  yellow  before 
the  blowpipe,  whereas  polymignite  re- 
tains its  black  colour. 

5.  Pyr-eneite.  A  greyish-black  mineral, 
occurring  in  primitive  limestone,  and 
consisting  of  silica,  alumina,  lime,  and 
iron. 

6.  Pyro-ligneous  Acid.  An  acid  ob- 
tained by  distillation  from  wood ;  in  its 
strongest  form  it  is  acetic  acid.  Pyro- 
ligneous  spirit  is  a  substance,  more  vola- 
tile than  alcohol,  produced  during  the 
distillation  of  wood.  It  is  more  correctly 
named  pyro-xylic  spirit. 

7.  Pyro-lusite.  The  most  abundant 
ore  of  manganese,  occurring  crystallized 
and  massive,  in  Devonshire,  Warwick- 
shire, Thuringia,  Brazil,  and  other 
places.  It  is  the  binoxide  of  peroxide  of 
manganese. 

8.  Pyro-meter  {fxerpov,  a  measure).  An 
instrument  for  measuring  all  degrees  of 
heat  above  those  which  can  be  indicated 
by  a  mercurial  thermometer.  Wedge- 
wood's  pyrometer  acts  by  the  contraction 
of  cylinders  of  fine  white  clay.  The  in- 
dications of  Daniell's  pyrometer  depend 
on  the  difference  in  the  expansion  and 
contraction  of  a  platinum  bar,  and  a 
tube  of  black  lead  ware  in  which  it  is 
contained. 

9.  Pyro-morphite  (p6pq>r\,  form).  Phos- 
phate of  lead,  generally  divided  into 
brown  lead  ore  and  green  lead  ore. 
When  heated  before  the  blowpipe,  it 
fuses  into  a  globule,  which  assumes  a 
polyhedral  crystalline  form  as  it  cools. 

10.  Pyr-ope.  Chrome  garnet,  gene- 
rally called  Bohemian  garnet,  occurring 
in  rounded  grains,  and  also  imbedded  in 
serpentine,  &c. 

11.  Pyr-orthite.  A  silicate  of  oxide  of 
cerium,  iron,  &c,  found  imbedded  in 
granite  or  quartz,  near  Fahlun  in  Swe- 
den. It  resembles  orthite,  but  is  differ- 
ently affected  by  heat. 

12.  Pyr-osmalite.  A  mineral  occurring 
in  magnetic  ironstone,  giving  out  vapours 
of  chlorine  before  the  blowpipe,  and  be- 
coming a  magnetic  oxide  of  iron. 

13.  Pyr-oxene.  The  name  given  by 
Haiiy  to  augite,  a  silicate  of  lime  and 


QUA 


QUA 


magnesia,  found  among  volcanic  rocks. 
It  has  received  various  names. 

14.  Pyro-phorous.  A  tenn  applied  to 
certain  substances  which,  by  the  absorp- 
tion and  condensation  of  the  aqueous 
vapour  and  gases  contained  in  the  atmo- 
sphere, become  heated  and  ignited,  as 
spongy  platinum,  which  absorbs  hydro- 
gen and  oxygen  so  readily,  and  then 
condenses  them,  that  its  entire  mass 
becomes  red-hot,  and  the  gas  is  ignited. 

15.  Pyro-phyllite.  A  green  radiated 
variety  of  talc  from  Siberia,  composed  of 
distinct  groups  of  small  diverging  la- 
minae. 

16.  Pyro-physalite.  A  sub-species  of 
prismatic  topaz,  from  Fahlun  in  Sweden. 

17.  Pyro-somata  (owfxa,  a  body).  A 
family  of  the  Tunicata,  consisting  of 
minute  animals  aggregated  together  in 
great  numbers,  so  as  to  form  a  hollow 
cylinder,  which  swims  in  the  sea  by  the 
combined  contractions  and  dilatations  of 
all  the  individuals  composing  it,  and  is 


capable  of  emitting  in  the  dark  a  brilliant 
phosphorescent  light,  or  body  of  fire,  as 
the  name  denotes. 

18.  Pyro-techny  (rexvn,  art).  The  art 
which  teaches  the  management  and  ap- 
plication of  fire  to  certain  operations ;  a 
term  commonly  applied  to  the  prepara- 
tion of  artificial  fireworks. 

PYRULI'NjE.  Pear-shells;  a  sub- 
family of  the  Turbinellidae,  or  Turnip- 
shells,  named  from  the  typical  genus 
pyrula,  and  characterized  by  the  short- 
ness of  the  spire,  by  the  smoothness  and 
convexity  of  the  pillar,  and  by  the  mode- 
rate length  of  the  canal. 

PYXI'DIUM  (pyxis,  a  box).  A  fruit 
which  dehisces  by  a  transverse  incision, 
so  that,  when  ripe,  the  seeds  and  their 
placenta  appear  as  if  seated  in  a  cup, 
covered  by  an  operculum  or  lid,  as  in 
hyoscyamus,  anagallis,  &c. 

PY'XIS  NAUTICA.  The  Mariner's 
Compass;  a  modern  southern  constella- 
tion, placed  in  Argo. 


a 


QUADRANT  (quadrans,  a  quarter). 
A  quadrant,  in  Geometry,  is  a  quarter  of 
a  circle.  The  term  also  denotes  an  in- 
strument for  measuring  angles,  consist- 
ing of  a  quarter  circle  of  wood  or  metal, 
having  its  circular  part,  or  limb,  divided 
into  90  parts,  or  degrees,  and  these  sub- 
divided into  minutes,  &c,  by  means  of 
a  Nonius  or  a  Vernier. 

1.  Hadley's  Quadrant  is  properly  an 
octant,  or  eighth  part  of  a  circle,  in 
which  the  angles  are  taken  by  means  of 
the  reflexion  of  light ;  and  when  the 
limb  is  extended  to  60  degrees  (the  sixth 
of  a  circle),  the  instrument  is  called  a 
Sextant. 

2.  Quadrant  of  Altitude.  The  name 
given  to  a  flexible  graduated  slip  of  brass, 
which  is  fixed  to  the  brazen  meridian  of 
the  globe.  By  this  the  distance  from  one 
point  of  the  globe  to  another  can  be  ob- 
tained in  degrees  of  arc.  But  as  other 
arcs  besides  altitudes  may  be  measured 
with  it,  it  is  sufficiently  distinguished  by 
calling  it  the  flexible  arc. 

QUADRANT  ELECTROMETER. 
An  instrument  for  estimating  the  degree 
or  intensity  of  electricity,  invented  by 
Mr.  Henley.  The  differences  of  electric 
intensity  are  denoted  by  an  index  which 
278 


traverses  a  quadrant  divided  into  ninety 
equal  parts,  called  degrees. 

QUADRA'NTAL.  A  name  formerly 
given  to  spherical  triangles,  one  side  of 
which  is  a  quadrant. 

QUADRATIC  EQUATIONS.  Qua- 
dratic  equations  are  divided  into  pure 
and  adfected.  Pure  quadratic  equations 
are  those  which  contain  only  the  square 
of  the  unknown  quantity,  as  x2  =  36 ; 
x2  +  5  =  54  ;  ax2—b  =  c;  &c.  Adfected 
quadratic  equations  are  those  which  in- 
volve both  the  square  and  the  simple 
power  of  the  unknown  quantity,  as  x2+ 
4a?  =  45;  3x*  —  2x  =  2l;  ax"2  +  2bx  = 
c  +  d;  &c. 

QUADRA'TRIX.  A  name  given  to 
a  curve  which  may  be  employed  in  the 
quadrature  of  other  curves.  Some  of 
these  have  been  specified ;  but,  after  all, 
the  description  of  these  curves  assumes 
the  point  which  they  are  intended  to  de- 
termine. 

QUADRATURE  (in  Astronomy).  The 
moon  is  said  to  be  in  her  quadrature, 
when  she  is  in  either  of  the  middle  points 
of  her  orbit,  between  her  conjunction 
and  opposition,  since  lines  from  the  earth 
to  the  moon  and  to  the  sun  include  a 
quadrant,  or  90  degrees.     Her  face  is 


QUA 

then  half-shown ;  it  is  bisected,  or  dicho- 
tomized. The  places  of  her  orbit,  where 
she  is  either  in  conjunction  or  opposition, 
are  her  syzygies. 

Quadrature  in  Geometry.  By  the  qua- 
drature of  a  curve  is  meant  the  finding 
of  a  square  equal  to  the  content  enclosed 
by  the  curve.  With  regard  to  the  famous 
problem  of  the  quadrature  of  the  circle —  ! 
since  the  whole  circular  area  is  equal  to 
the  rectangle  under  the  radius  and  a 
straight  line  equal  to  half  the  circum- 
ference, the  object  in  squaring  the  circle 
is  to  determine  the  ratio  of  the  circum- 
ference to  the  diameter,  and  this  can  only 
be  expressed  by  infinite  series. 

QUADRILATERAL  (quatuor  latera 
habens).  Having  four  sides  ;  as  applied 
to  a  plane  geometrical  figure,  bounded 
by  four  straight  lines.  Such  a  figure  is 
also  called  a  quadrangle. 

QUADRU'MANA  ( quatuor,  four,  ma- 
nus,  a  hand).  Four-handed ;  the  desig- 
nation of  an  order  of  Mammalia,  includ- 
ing the  monkey,  the  lemur,  &c,  which 
have  a  moveable  thumb  on  their  lower 
extremities  opposed  to  the  fingers ;  all 
their  extremities  are,  in  fact,  instru- 
ments of  prehension. 

QUALITY  OF  PROPOSITIONS.  In 
Logic,  propositions  are  divided  according 
to  the  quality  of  their  expression,  which 
is  here  the  essential  circumstance,  into 
affirmative  and  negative;  and  according 
to  the  quality  of  their  matter,  which  is 
accidental,  into  true  and  false. 

QUANTITY  (quantus,  how  much). 
Quantity  is  distinguished  into  continued 
and  discrete.  It  is  continued,  when  the 
parts  are  connected  together,  and  is  then 
termed  magnitude,  which  is  the  object  of 
geometry.  It  is  discrete,  when  the  parts 
have  an  unconnected  and  independent 
existence,  and  then  constitutes  multi- 
tude or  number,  which  is  the  object  of 
arithmetic. 

1.  Quantity,  negative.  The  difficulty 
attending  the  use  of  a  minus  or  negative 
quantity,  in  algebraic  operations,  is  re- 
moved at  once  by  viewing  it,  as  it  always 
must  be  viewed,  in  reference  to  another 
quantity,  which  is  plus  or  positive.  A 
debt  may  be  regarded  as  a  negative  quan- 
tity, inasmuch  as  it  is  a  quantity  to  be 
subtracted  in  case  of  there  being  any 
property  (which  is  positive),  from  which 
to  subtract  it.    So  also, 

4  —  2  =  2; 
4  —  2  x  4  —  2  =  4; 

Hence,  —  2  is  in  reality  —  (+  2);  it 
279 


QUA 

is  the  plus  or  real  quantity  4,  —  the  real 
quantity  2. 

Thus,  a  —  quantity  =  a  —  (+  quan- 
tity). 

2.  Quantity  fractional.  It  has  excited 
surprise  that  £  x  \  should  be  ^.  Let  the 
question  be  tried  geometrically,  and  the 
difficulty  vanishes.  It  is  only  necessary 
to  consider  £  as  the  J  of  a  line  1 ;  and 
the-jk  as  the  ^  of  the  square  of  the 
same  line.     Thus— 

\  linear. 

* ^  square. 


Thus,  the  square  of  \  of  1  linear  is  ^  of 
1  square ;  the  square  of  £  linear  is  £ 
superficial ;  and  the  square  of  £  linear 
is  fy,  or  £  +  ^.  All  this  would  be  evi- 
dent if,  instead  of  multiplication,  we  used 
the  term  quadration,  or  (if  admissible) 
parallelogramization. 

3.  Quantity,  impossible  or  imaginary. 
If  an  expression  occur  under  the  form 
\/  —  a,  this  indicates  an  impossibility; 
for  it  signifies  the  square  root  of  a  nega- 
tive quantity,  which  has  no  existence, 
since  there  is  no  quantity,  positive  or 
negative,  which,  being  multiplied  by 
itself,  gives  a  negative  result.  An  im- 
possible quantity,  or,  in  other  words,  the 
even  root  of  a  negative  quantity,  may  be 
expressed  in  the  form  of  a  surd,  as 
s/  ~8|  \J  —  a2,  &c. ;  the  difference  be- 
tween surd  and  impossible  quantities 
being  that  the  former  have  real  values, 
though  we  cannot  exactly  find  them, 
while  there  cannot  be  a  quantity,  posi- 
tive or  negative,  an  even  power  of  which 
would  produce  a  negative  quantity. 

QUANTITY  OF  PROPOSITIONS. 
In  Logic,  propositions  are  divided  ac- 
cording to  their  quantity,  or  extent:  if 
the  predicate  is  said  of  the  whole  of  the 
subject,  the  proposition  is  universal;  if 
of  a  part  of  it  only,  the  proposition  is 
particular;  in  the  former,  the  subject  is 
distributed,  or  stands  for  the  whole  of  its 
significates ;  in  the  latter,  it  is  not  dis- 
tributed, and  stands  for  a  part  only  of  its 
significates. 

QUANTITY  and  TANTITY.  These 
terms  are  employed  by  Mr.  Mill,  in  his 
"  Elements  of  the  Human  Mind,"  as  cor- 
relative, or,  as  he  terms  them,  connota- 
tive ;  the  word  quantus,  how  much,  being 


R  AC 


RAC 


answered  by  tantus,  so  much.  The  com- 
mon use,  however,  of  the  former  word 
renders  the  latter  superfluous.  The 
term  quantuplicity,  as  distinguished  from 
quantity,  means  the  answer  to  "  how 
many  times,"  as  distinguished  from 
"how  much:" 

QUA-QUA-VERSAL  DIP  {qud-qud- 
versum,  on  every  side).  The  dip  of  geo- 
logical beds  to  all  points  of  the  compass 
around  a  centre,  as  in  the  case  of  beds 
of  lava  round  the  crater  of  a  volcano. 

QUART A'TION  (quartus,  the  fourth). 
An  operation  by  which  the  quantity  of 
one  substance  is  made  equal  to  a  fourth 
part  of  the  quantity  of  another:  thus,  in 
separating  gold  from  silver,  three  parts 
of  silver  are  added  to  the  supposed  gold, 
and  they  are  then  fused  together,  the 
gold  thus  becoming  at  most  one-fourth 
of  the  mass  only.  They  are  then  parted 
by  the  action  of  nitric  acid. 

QUARTILE.  A  term  formerly  em- 
ployed in  Astronomy  to  denote  an  aspect 
of  two  places  when  their  longitudes  differ 
by  90  degrees,  or  a  fourth  part  of  the 
circle. 

QUARTINE  {quartus,  fourth).  The 
name  of  the  fourth  membrane  or  enve- 
lope of  the  nucleus  in  plants,  as  described 
by  Mirbel. 

QUARTZ.  A  German  provincial  term, 
universally  adopted  in  scientific  lan- 
guage for  a  simple  mineral,  composed  of 
pure  silex,  or  earth  of  flints,  extremely 
abundant  in  nature,  from  the  common 
pebble  to  large  mountain  veins,  and  even 
entire  rocks.     See  Rock  Crystal. 

QUARTZITE,  or  QUARTZ  ROCK. 
An  aggregate  of  grains  of  quartz,  some- 
times passing  into  compact  quartz. 

QUATERNARY  (quaternarius,  of  the 
number  four).    A  term  applied  in  che- 


mistry to  those  compounds  which  con- 
tain four  elements,  as  gum,  fibrin,  &c. 
The  term  is  also  applied  to  any  arrange- 
ment in  which  the  prevailing  number  is 
four,  as  in  the  floral  envelopes  of  Cruci- 
ferous plants,  &c. 

QUE'RCITRIN.  The  yellow  colour- 
ing matter  of  quercitron  bark.  As  it 
restores  the  colour  of  reddened  litmus 
paper,  and  combines  with  and  neutralizes 
bases,  it  has  been  considered  an  acid, 
and  named  quercitronic  acid. 

QUICKLIME.  The  protoxide  of  cal- 
cium, obtained  by  exposing  carbonate  of 
lime  to  a  strong  red  heat,  so  as  to  expel 
its  carbonic  acid. 

QUI'NARY  {quinarius,  of  the  number 
five).  A  term  applied  to  a  system  in 
which  the  prevailing  number  is  five,  as 
observed  in  the  floral  envelopes  of  most 
dicotyledonous  plants. 

QUINCUNX.  In  Botany  a  form  of 
aestivation  or  vernation,  in  which  there 
are  five  leaves,  two  of  which  are  exterior, 
two  interior,  and  the  fifth  covers  the  in- 
terior with  one  margin,  while  its  other 
margin  is  covered  by  the  exterior,  as  in 
the  rose. 

QUINDE'CAGON.  A  geometrical 
figure  bounded  by  fifteen  sides. 

QUINTILE.  A  term  formerly  em- 
ployed in  Astronomy,  to  denote  a  dis- 
tance in  longitude  of  72  degrees,  or  a 
fifth  part  of  the  circle. 

QUI'NTINE  (quintus,  fifth).  The  fifth 
membrane  or  envelope  of  the  nucleus  of 
plants,  as  described  by  Mirbel.  This  is 
the  vesicula  amnios  of  Malpighi,  the 
"  additional  membrane"  of  Brown,  and 
the  sac  of  the  embryo  of  Brongniart. 

QUOTIENT  or  QUOTE  (quoties,  how 
often).  The  result  of  dividing  one  num- 
ber by  another. 


R 


RABDOTLOGY  (pd/33or,  a  rod,  \6yot, 
a  description),  Rhabdology.  A  method 
for  performing  the  arithmetical  operations 
of  multiplication  and  division,  by  means 
of  an  instrument  invented  by  Lord  Na- 
pier, and  termed  from  him  Napier's  rods 
or  bones.  The  mode  of  calculation  is 
tedious,  and  is  now  superseded  by  the 
use  of  logarithms. 

RACES  OF  MAN.  Under  the  terms 
Caucasian,  Mongolian,  American,  Ethio- 
pian, and  Malay  Race,  will  be  found  the 


characteristics  of  these  divisions,  accord- 
ing to  Blumenbach.  The  Races  are  dif- 
ferent forms  of  one  species,  capable 
of  fruitful  union,  and  propagated  by 
generation. 

RA'CEME  (racemus,  a  bunch  of 
grapes).  A  form  of  inflorescence,  in 
which  all  the  buds  of  an  elongated 
branch  are  developed  as  flower-buds, 
and  at  the  same  time  produce  peduncles, 
as  in  hyacinth. 

RACE'MIC  ACID  (racemus,  a  bunch 


RAD 


R  A  I 


of  grapes).  Paratartaric  Acid.  An  acid 
obtained  from  the  grape,  similar  in  its 
composition  to  tartaric  acid,  with  which 
it  is  consequently  isomeric. 

RA'CHIS  (pdxi*,  a  ridge).  This  term, 
which  should  be  written  rhachis,  denotes, 
in  Botany,  that  form  of  floral  axis  in 
which  several  pedicles,  or  flower-stalks, 
are  developed  at  short  distances  from 
each  other,  as  in  grasses. 

RA'DIANT  {radius,  a  ray).  In  Geo- 
metry, a  radiant  is  a  straight  line  pro- 
ceeding from  a  given  point,  or  fixed 
pole,  about  which  it  is  conceived  to 
revolve. 

RA'DIANT  POINT.  That  point  from 
which  the  rays  of  light  diverge  from  a 
luminous  body  in  all  directions.  The 
point  in  which  convergent  rays  meet,  is 
the  focus. 

RADIA'RIA  (radius,  a  ray).  A  term 
applied  by  Lamarck  to  that  class  of  the 
Radiata  of  Cuvier,  which  contains  species 
with  a  radiated  form  of  the  entire  body. 
They  are  distinguished  into  the  soft  and 
gelatinous,  as  the  medusa ;  and  the  hard, 
spiny,  and  echinodermal  species,  as  the 
asterias. 

RADIA'TA  (radius,  a  ray).  The  de- 
signation of  animals,  most  of  which  are 
disposed  around  an  axis  in  a  radiated 
form,  as  the  star-fish.  They  compose 
one  of  the  four  great  divisions  of  the 
animal  kingdom. 

RADIA'TION  (radius,  a  ray).  A  term 
applied  to  the  emission  of  light,  or  of 
heat,  from  the  surface  of  a  luminous  or  of 
a  heated  body,  in  the  form  of  radii,  or 
rays.  In  natural  philosophy,  whatever 
sends  forth  emissions  in  all  directions,  is 
said  to  radiate ;  and  hence  we  have  radi- 
ation, not  only  of  heat  and  of  light,  but 
also  of  sound. 

RADICAL  (radix,  a  root).  A  term 
applied  generally  to  any  substance  which 
is  capable  of  combining  with  simple 
bodies.  A  radical  is  termed  simple,  when 
it  is  itself  an  elementary  body,  as  chlorine 
in  hydrochloric  acid ;  or  compound,  when, 
though  itself  a  compound,  it  acts  as  a 
simple  body  in  its  modes  of  combination, 
as  cyanogen  in  the  cyanides.  In  general 
terms,  a  radical,  simple  or  compound, 
forms  an  acid  with  hydrogen,  and  a  salt 
with  a  metal. 

RA'DICAL  SIGN  (radix,  a  root).  In 
Algebra,  the  radical  sign  is  the  symbol 
„J,  and  denotes  the  extraction  of  a  root. 
It  is  a  modification  of  the  letter  r,  the 
initial  letter  of  radix,  or  root.  See 
Boot. 

281 


RA'DICLE  (radicula,  a  little  root)- 
The  rootlet,  or  the  rudiment  of  the  de- 
scending axis  of  plants,  as  it  occurs  in 
the  embryo. 

RA'DIUS.  A  rod  ;  a  spoke  of  a  wheel. 
The  semi-diameter  of  a  circle,  or  a  right 
line  drawn  from  the  centre  of  a  circle  to 
the  circumference. 

1.  Radius  of  Curvature.  In  speaking 
of  the  concavity  of  other  curves  than  the 
circle,  the  radius  of  curvature  at  a  given 
point  is  the  radius  of  a  circle  which  has 
the  same  curvature  as  the  curve  has  at 
that  point. 

2.  Radius  Vector.  The  radius  vector 
is  a  right  line  drawn  from  the  centre  of 
force  (in  any  curve,  on  which  a  body  is 
supposed  to  move  by  centripetal  force) 
to  that  point  of  the  curve  where  the  body 
is  supposed  to  be.  It  is  a  general  radius 
to  the  curve,  and  has  the  addition  of 
Vector,  or  carrier,  because  it  is  imagined 
to  carry  forward  the  body  to  which  it  is 
attached.  The  earth,  for  example, 
moves  in  an  elliptic  orbit,  of  which  the 
sun  (the  centre  of  force)  is  in  one  of  the 
foci;  and,  by  consequence,  the  radius 
vector  is  continually  increasing  in  length 
during  her  course  from  the  perihelion  to 
the  aphelion,  and  decreasing  in  the  same 
proportion  in  the  progress  of  her  return.. 

RA'DIX.  Literally,  a  root ;  and, 
hence,  applied,  in  arithmetic,  to  the  fun- 
damental of  any  system  of  numeration. 
Thus,  10  is  the  radix  of  the  decimal  sys- 
tem, and  of  the  common  system  of  loga- 
rithms. 

RAIN.  When  the  temperature  of  the 
air  is  above  32°,  or  the  freezing  point,  the 
water  separated  from  the  air  falls  to  the 
earth  in  the  state  of  rain.  It  is  generally 
thought  that  the  precipitation  of  water 
from  the  atmosphere  is  the  effect  of  the 
mingling  together  of  currents  of  warm 
and  of  cold  air. 

RAINBOW.  A  meteor  in  form  of  a 
party-coloured  arch,  or  semicircle,  ex- 
hibited only  at  the  time  when  it  rains. 
It  is  always  seen  in  that  point  of  the 
heavens  which  is  opposite  to  the  sun, 
and  is  occasioned  by  the  refraction  and 
reflection  of  his  rays  in  the  drops  of  fall- 
ing rain.  The  secondary  rainbow  may 
be  explained  by  supposing  a  double  re- 
fraction and  reflection  of  the  sun's 
beams. 

RAIN  GAUGE.  An  instrument  for 
ascertaining  the  comparative  quantity  of 
rain  which  falls  in  different  places  and  in 
different  seasons.  It  is  sometimes  called 
pluviometer. 


RAR 


RAT 


RA'LLIDvE  (rallus,  the  rail).  The 
Rail  tribe ;  a  family  of  the  Grallatores, 
or  Wading  birds,  characterized  by  the 
extreme  length  of  the  toes. 

RAME'NTA  (rado,  to  scrape  off). 
Filings,  as  of  a  metal.  In  Botany,  the 
term  denotes  the  thin,  brown,  foliaceous 
scales,  which  appear  on  the  back  of  the 
fronds  of  ferns,  &c. 

RAMO'SE  (ramosus,  branched).  A 
term  applied  to  those  spines  upon  shells 
which  send  out  others  in  a  lateral  direc- 
tion. 

RAMPHA'STIDjE  (ramphastos,  the 
toucan).  The  Toucans ;  a  family  of 
Scansorial  birds,  placed  by  Cuvier  in  his 
third  order,  Grimpeurs,  between  the  anis 
(Crotophaga)  and  the  parrots. 

RANCI'DITY.  The  change  which 
oils  undergo  by  exposure  to  the  air.  It 
depends  on  the  combination  of  oxygen 
with  the  extractive  principle,  which  is 
naturally  united  with  the  oily  principle. 
The  result  is,  therefore,  analogous  to  the 
oxidation  of  metals. 

RA'NID^E  {rana,  a  frog).  The  Frog 
tribe ;  one  of  the  principal  divisions  of 
the  Anoural  order  of  Amphibious  ani- 
mals, which  pass  from  the  tadpole  to  the 
perfect  state,  and  are  adapted  for  aquatic 
life.    See  Bufoidce. 

RANUNCULA'CEjE.  The  Crowfoot 
tribe  of  Dicotyledonous  plants.  Herba- 
ceous plants  with  divided  leaves,  opposite 
or  alternate  ;  calyx  of  3-6  petals ;  petals 
5-15,  hypogynous ;  stamens  hypogynous, 
indefinite  in  number ;  fruit  distinct, 
simple  carpella,  and  albuminous  seeds. 

RA'PHIDES  (pa<pk,  a  needle).  Small 
acicular  crystals,  found  within  the  cells 
of  the  parenchyma  of  certain  plants. 

RAPTO'RES  {raptor,  a  snatcher). 
Raptrices.  Plunderers,  or  Birds  of  Prey; 
an  order  of  birds,  characterized  by  the 
robustness  and  muscularity  of  the  whole 
body,  by  the  strength  of  the  legs  and  of 
the  bill  and  talons,  by  their  rapacious 
habits,  solitary  disposition,  great  quick- 
ness of  sight,  and  powerful  flight.  They 
are  distinguished  into  the  diurnal,  con- 
taining the  vultures,  eagles,  falcons,  &c, 
and  the  nocturnal,  or  the  owls. 

RAREFA'CTION  {rarus,  thin,  facio, 
to  make).  The  act  of  rendering  a  sub- 
stance less  dense ;  also,  the  condition  of 
diminished  density.  The  term  is  gene- 
rally applied  to  elastic  fluids,  which  ex- 
pand on  the  application  of  heat,  or  in 
consequence  of  partial  exhaustion,  and 
thence  become  thinner  or  more  rarefied. 
RA'RITY  (rarus,  thin).  A  property 
282 


of  matter  opposed  to  density,  and  denoting 
a  thinness  or  subtlety  of  bodies  :  mercury 
is  a  dense  fluid,  ether  a  rare  one.  The 
term  is  generally  applied  to  aeriform 
bodies,  those  of  dilatation  and  expansion 
being  employed  in  speaking  of  solids  and 
liquids. 

RAS  ALGRATHA.  A  star  of  the 
third  magnitude  in  the  northern  constel- 
lation Hercules.  Ras  Aliagus  is  the 
principal  star  in  the  northern  constella- 
tion Serpentarius. 

RASO'RES  (rado,  to  scratch).  Ra- 
drices.  Scratchers  ;  an  order  of  gallina- 
ceous Birds,  so  named  from  the  general 
habit  which  these  graminiferous  species 
present  of  scratching  up  the  soil  to  ob- 
tain their  food.  The  only  general  cha- 
racter of  the  order  is  derived,  according 
to  Macgillivray,  from  the  digestive 
organs.  "  A  very  large  dilatation  of  the 
oesophagus,  forming  a  crop,  lying,  when 
distended,  equally  on  both  sides  of  the 
neck,  and  such  an  enlargement  of  the 
coeca  as  to  render  their  capacity  at  least 
half  of  that  of  the  intestine,  occur  toge- 
ther in  no  other  birds.  It  is  very  diffi- 
cult to  assign  general  characters  of  any 
other  kind  to  them." 

RA'STABER.  A  star  of  the  third 
magnitude  in  the  northern  constellation 
Draco. 

R  A'THOFFITE.  A  species  of  garnet, 
found  in  Sweden,  accompanied  by  calc- 
spar  and  hornblende. 

RA'TIO.  When  two  subjects  admit 
of  comparison,  with  reference  to  some 
quality  which  they  possess  in  common, 
and  which  may  be  measured,  this  mea- 
sure is  their  ratio,  or  the  rate  in  which 
one  exceeds  the  other.  With  this  term 
is  connected  that  of  proportion,  which 
denotes  the  portions,  or  parts  of  one  mag- 
nitude which  are  contained  in  another. 
In  the  language  of  Mathematics,  the 
term  ratio  has  been  adopted  to  express 
what  is  more  generally  understood  by 
the  term  proportion  :  thus,  instead  of 
"  the  proportion  which"  one  thing  bears 
to  another,  we  say,  "  the  ratio  which " 
one  bears  to  the  other,  meaning  its  com- 
parative magnitude ;  instead  of  saying 
that  A  is  to  B  "in  the  proportion  of 
5  to  6,"  we  say,  "in  the  ratio  of  5  to  6." 

I.  When  the  ratio  is  commensurable 
(that  is,  when  it  is  reducible  to  numbers), 
it  is  equivalent  to  proportion  ;  the  latter 
term  is,  however,  usually  employed  in 
the  comparison  of  ratios,  in  which  case 
two  ratios  are  said  to  be  proportionals. 
Thus,  3  has  to  4  a  certain  ratio,  or  pro- 


RAT 

portion;  but  the  expression  3  is  to  4  in 
the  same  proportion  as  6  to  8,  denotes 
that  the  ratios  of  3  to  4  and  6  to  8  are 
equal ;  3  bearing  the  same  proportion 
to  4,  as  6  to  8,  that  is,  being  three-fourths. 
Ratios,  however,  may  be  unequal.  Thus 
it  is  said  that  the  ratio  of  9  to  4  is  greater 
than  that  of  7  to  6,  because  ^  is  greater 
than  £  ;  it  being  thus  that  ratios  are 
measured. 

2.  Ratio,  direct.  When  two  quantities, 
or  magnitudes,  have  a  certain  ratio  to 
each  other,  and  are,  at  the  same  time, 
subject  to  increase  or  diminution;  if, 
while  one  increases,  the  other  increases 
in  the  same  ratio,  or  if,  while  the  one 
diminishes,  the  other  diminishes  in  the 
same  ratio,  the  proportions,  or  compari- 
sons of  ratios,  remain  unaltered,  and 
those  quantities,  or  magnitudes,  are  said 
to  be  in  a  direct  ratio  or  proportion  to 
each  other.  Thus  if  a  yard  of  cloth  be 
worth  a  pound,  ten  or  any  number  of 
yards  will  be  worth  so  many  pounds,  and 
the  proportion  of  value  continues  un- 
altered. 

3.  Ratio,  inverse.  But,  if  the  quan- 
tities, or  magnitudes,  are  such,  that, 
when  one  increases,  the  other  necessarily 
diminishes ;  and  vice  versd,  when  the 
one  diminishes,  the  other  increases,  the 
ratio,  or  proportion,  is  said  to  be  inverse. 
Thus,  there  is,  at  any  moment,  a  certain 
ratio  of  the  length  of  the  day  to  that  of 
the  night;  but  this  is  an  inverse  ratio, 
for  in  proportion  as  the  length  of  either 
increases,  that  of  the  other  must  dimi- 
nish. 

4.  Ratio,  compound.  A  compound 
ratio  is  made  up  of  the  product  of  two, 
or  more,  simple  ratios ;  that  is,  of  the 
product  of  their  first  terms,  which  are 
called  antecedents,  compared  with  the 
product  of  their  second  terms,  called 
consequents.  Thus  24  :  3  is  a  compound 
ratio  of  4  :  1  and  6:3;  this,  being 
made  up  of  two  simple  ratios,  is  called  a 
duplicate  ratio.  When  three  simple 
ratios  are  compounded,  they  form  a  tri- 
plicate ratio  ;  when  four,  a  quadruplicate 
ratio  ;  and  so  of  other  compounds. 

5.  Ratio,  Extreme  and  Mean.  A  line 
is  said  to  be  so  divided,  when  the  rect- 
angle under  the  whole  line  and  the  lesser 
segment  is  equal  to  the  square  of  the 
greater  segment ;  and,  hence,  the  whole 
line  is  to  the  greater  segment,  as  that 
greater  segment  is  to  the  lesser.  The 
segments  of  such  a  division,  being  in- 
commensurable with  the  whole  line, 
cannot  be  exactly  given  in  numbers,  but 


RE  A 

the    geometrical    construction    is    easy. 
See  Euclid's  Elements,  book  ii.  prop.  11. 

RATIONAL  QUANTITY.  A  quan- 
tity, algebraic  or  arithmetical,  which  can 
be  expressed  without  the  use  of  the  signs 
of  evolution,  such  as  those  of  the  square 
root,  the  cube  root,  &c.  See  Irrational 
Number. 

RAY  [radius,  a  beam  or  rod).  A  single 
radiation,  or  the  smallest  form  in  which 
light  or  caloric  is  emitted  from  bodies. 
Calorific  rays  are  those  rays  which  excite 
heat ;  luminous  rays,  those  which  impart 
light ;  chemical  rays,  those  which,  with- 
out producing  heat  or  light,  produce 
chemical  change,  as  that  of  darkening 
the  white  chloride  of  silver.  The  last 
are  also  called  deoxidizing  or  hydro- 
genating  rajs,  from  their  characteristic 
effect  in  withdrawing  oxygen  from  water 
and  other  oxides. 

REA'CTION.  The  resistance  made 
by  all  bodies  to  the  action  or  impulse  of 
others,  which  endeavour  to  change  their 
state,  either  of  motion  or  of  rest.  Action 
and  reaction  are  always  equal  to  each 
other ;  that  is,  the  effect  which  any  force 
exerts— or,  what  is  the  same,  its  mo- 
mentum —  is  equal  to  the  resistance 
which  the  body  it  sets  in  motion  offers 
to  it.  The  intensity  of  the  moving  power 
is  therefore  estimated  by  the  mass  and 
velocity  of  the  body  set  in  motion. 

REAGENT  or  TEST.  In  Chemistry, 
a  substance  which  indicates  the  presence 
of  any  body  existing  in  a  minute  propor- 
tion in  a  solution,  by  rendering  it  turbid, 
by  imparting  a  particular  colour  to  it,  or 
by  depositing  a  precipitate.  Thus,  a 
solution  of  nitrate  of  silver  is  a  most 
powerful  reagent  in  detecting  chloride  of 
sodium. 

REAL  DEFINITION.  A  definition 
which  explains  the  nature  of  the  thing 
defined  ;  viz.  either  the  whole  nature  of 
it,  as  in  Mathematics,  or  else  something 
heyond  what  is  necessarily  understood 
by  the  term  (see  Nominal  Definition). 
In  the  strict  sciences,  the  nominal  and 
the  real  definition  exactly  coincide ;  the 
meaning  of  the  word,  and  the  nature  of 
the  thing,  being  exactly  the  same.  This 
holds  good  also  with  respect  to  logical 
terms,  most  legal,  and  many  ethical 
terms. 

REA'LGAR.  The  protosulphuret  of 
arsenic.  It  is  either  native,  and  dug  out 
of  the  earth  in  China;  or  factitious,  pro- 
cured by  boiling  orpiment,  or  the  sesqui- 
sulphuret,  in  subliming  vessels. 

RE'ALISM.    The  opinion  of  a  class  of 


RE  C 


REC 


philosophers,  that  Genus  and  Species  are 
some  real  Things,  existing  independ- 
ently of  our  conceptions  and  expressions  ; 
and  that,  as  in  the  case  of  Singular  terms 
there  is  some  real  individual  correspond- 
ing to  each,  so,  in  Common  terms  also, 
there  is  some  Thing  corresponding  to 
each ;  which  is  the  object  of  our  thoughts 
when  we  employ  any  term.  This  doc- 
trine, though  attributed  to  Aristotle,  is 
by  him  expressly  contradicted.  See 
Nominalists. 

REASON.  Whately  has  pointed  out 
several  of  the  ambiguities  to  which  this 
word  is  liable.     It   is  used  to  signify, 

1,  all  the  intellectual  powers  collectively; 

2,  those  intellectual  powers  exclusively 
in  which  man  differs  from  brutes ;  3,  the 
faculty  of  carrying  on  the  operation  of 
the  mind,  which  logicians  call  reason- 
ing;  4,  the  premiss  or  premises  of  an 
argument,  especially  the  minor  premiss  ; 
and  it  is  from  Reason  in  this  sense 
that  the  word  "Reasoning"  is  derived; 
5,  lastly,  it  is  often  used  to  signify  a 
cause,  as  when  we  say,  in  popular  lan- 
guage, that  the  "  Reason  of  an  eclipse 
of  the  sun  is,  that  the  moon  is  inter- 
posed between  it  and  the  earth."  This 
should  be  strictly  called  the  cause. 

"  What  adds  to  the  confusion  is,  that 
the  Cause  is  often  employed  as  a  Proof  of 
the  effect :  as  when  we  infer,  from  a 
great  fall  of  rain,  that  there  is,  or  will 
be,  a  flood ;  which  is  at  once  the  physical 
effect,  and  the  logical  conclusion.  The 
case  is  just  reversed,  when  from  a  flood 
we  infer  that  the  rain  has  fallen." 

REASONING  IN  A  CIRCLE.  A 
fallacious  mode  of  reasoning,  in  which 
the  truth  of  a  proposition  is  asserted  by 
adducing  the  conclusion.  The  following 
is  Whately's  illustration  : — "  To  allow 
every  man  an  unbounded  freedom  of 
speech  must  always  be,  on  the  whole, 
advantageous  to  the  state  ;  for  it  is  highly 
conducive  to  the  interests  of  the  com- 
munity, that  each  individual  should  en- 
joy liberty,  perfectly  unlimited,  of  ex- 
pressing his  sentiments." 

RECEIVER.  A  glass  vessel  employed 
in  pneumatical  experiments  for  contain- 
ing the  object  on  which  an  experiment 
is  to  be  exhibited  by  means  of  the  air- 
pump.  In  Chemistry,  the  term  denotes 
a  vessel  fitted  to  the  neck  of  a  retort, 
alembic,  &c,  for  the  purpose  of  receiving 
the  products  of  distillation. 

RECE'PTACLE.  In  Botany,  the  di- 
lated and  depressed  axis  of  the  inflores- 
cence termed  capitulum,  constituting  the 
284 


seat  of  the  artichoke,  &c.  The  receptacle 
is  called  torus  or  thalamus,  and  in  Greek 
compounds  has  the  name  of  clinium.  To 
this  part  may  be  referred  the  gynophore, 
the  polyphore,  and  the  gynobase  of  bo- 
tanical writers. 

RECI'PROCAL  (reciprocus,  mutual; 
flowing  backward  or  forward).  A  term 
employed  in  mathematics  to  denote  a 
fraction  which  is  formed  by  inverting 
another  fraction ;  thus  %  is  the  reciprocal 
of  1 ;  and  L  the  reciprocal  of  7  or  ^  A 
reciprocal  property  is  that  which  each  of 
two  things  has  with  reference  to  the 
other;  thus,  if  A  and  B  are  what  is 
called  conjugate  diameters  of  a  conic 
section,  the  tangent  at  either  extremity 
of  A  is  parallel  to  B,  and  that  at  either 
extremity  of  B  is  parallel  to  A.  Hence, 
these  lines  are  reciprocally  connected 
with  each  other,  and  are  therefore  called 
conjugate ;  for  the  term  conjugate,  which 
denotes  joined,  generally  means  joined 
by  a  reciprocal  property. 

RECTA'NGLE  {rectum  angulum  ha- 
bens).  A  geometrical  term,  denoting  a 
right-angled  parallelogram,  or  any  figure 
of  which  all  the  angles  are  right  angles. 
A  rectangle  is  said  to  be  contained  by  any 
two  of  its  adjoining  sides.  The  areas  of 
all  figures  whatever,  whether  bounded  by 
straight  lines  or  curves,  are  expressed  by 
those  of  equivalent  rectangles. 

RECTIFICATION.  In  Chemistry, 
the  repeating  of  a  distillation  or  a  sub- 
limation several  times,  in  order  to  ren- 
der the  substance  purer  and  finer. 

RECTIFICATION  (in  Mathematics). 
The  finding  of  a  right  line  equal  in  length 
to  an  arc  of  a  curve.  The  term  is  thus 
analogous  to  that  of  quadrature,  as  ap- 
plied to  the  finding  of  its  area ;  for  as  an 
area  is  considered  to  be  found  when  a 
square  equal  to  it  has  been  exhibited,  so 
the  length  of  an  arc  is  known  when  a 
straight  line  equal  to  it  has  been  found. 

RECTILI'NEAL  (recta  linea,  a  right 
line).  A  term  applied  in  Geometry  to  all 
figures  which  are  contained  by  right  lines, 
as  a  triangle,  a  square,  &c. 

RECURRING  DECIMAL.  Circula- 
ting Decimal.  For  the  exact  expression 
of  a  vulgar  fraction  by  a  decimal,  the 
former  must  either  have,  or  be  capable  of 
being  reduced  to  another  which  has  10 
or  some  power  of  10  for  its  denominator. 
Otherwise,  the  decimal  will  go  on  inter- 
minably, the  same  figure  or  figures  recur- 
ring in  the  same  order.  These  are  called 
recurring,  repeating,  or  circulating  deci- 
mals, and  the  part  repeated  is  called  the 


REF 


REP 


period  or  repetend.  A  pure  circulator  is 
one  in  which  the  period  begins  imme- 
diately after  the  point;  all  others  are 
called  mixed. 

RED  CHALK.  Red  clay,  or  reddle  ; 
an  argillaceous  iron-stone  ore. 

RED  FIRE.  A  pyrotechnical  com- 
pound of  nitrate  of  strontia,  sulphur, 
antimony,  and  chlorate  of  potash,  which 
burns  with  a  red  flame. 

RED  LEAD.  Minium.  An  oxide  of 
lead  with  a  fine  red  colour,  with  a  shade 
of  yellow.  It  is  intermediate  between 
the  protoxide  and  the  peroxide. 

RED  MARL.  Variegated  Red  Sand- 
stone ;  a  sandstone  with  an  argillaceous 
cement,  often  containing  beds  of  red  or 
variegated  marl,  and  subordinate  beds  of 
reddish  oolite  and  dolomite,  with  clays 
containing  gypsum  and  salt. 

RED  PRECI PITATE.  The  red  oxide 
of  mercury,  or  mercuric  oxide,  obtained 
by  the  decomposition  of  the  nitrate  of 
mercury  by  heat. 

REDU'CTION.  A  rule  in  arithmetic 
by  which  we  find  the  quantity  in  one  de- 
nomination corresponding  to  a  quantity 
expressed  in  another  denomination;  by 
which,  for  example,  we  find  how  many 
shillings  there  are  in  a  certain  number  of 
pounds,  how  many  pounds  in  a  certain 
number  of  shillings,  &c.  In  the  former 
case  the  reduction  is  termed  descending, 
and  is  performed  by  multiplication ;  in 
the  latter  it  is  ascending,  and  is  per- 
formed by  division. 

REDU'CTION  OF  METALS.  The 
conversion  of  the  oxides  of  metals  into 
the  metallic  state,  by  the  application  of 
heat;  the  operation  consists  in  mixing 
them  with  some  substance  which  will 
attract  the  oxygen  from  the  oxides ;  coal 
is  the  substance  generally  employed  for 
this  purpose. 

REEF,  or  CORAL  REEF.  A  pecu- 
liar kind  of  rock  produced  by  the  coral 
animalcule,  found  in  the  ocean,  of  con- 
siderable length,  of  very  narrow  width, 
and  generally  only  a  few  feet  below  the 
surface  of  the  water.  Reefs  are  usually 
of  a  circular  or  oval  form,  surrounded  by 
a  deep  sea,  the  interior  generally  pre- 
senting the  appearance  of  a  shallow 
lagoon.  But  they  appear  under  various 
forms. 

REFERENCES,  FALLACY  OF.  An 
artifice  sometimes  employed  by  dishonest 
writers,  consisting  in  the  merely  giving 
of  references  to  authorities,  which  may 
be  conceived  favourable  to  the  writers' 
views ;  it  is  supposed  that  few  will  take 
285 


the  trouble  of  examining  the  passages 
referred  to,  and  that  the  confirmation  of 
the  writers'  statements  by  such  authori- 
ties will  be  taken  for  granted. 

REFINING.  The  operation  of  puri- 
fying anything;  particularly  the  assay- 
ing or  purifying  of  gold  and  silver,  by 
separating  them  from  other  bodies  which 
are  combined  with  them. 

REFLECTING  CIRCLE.  An  astro- 
nomical instrument  destined  for  the 
same  uses  as  the  sextant,  but  more  com- 
plete, the  circle  being  entire,  and  the 
divisions  carried  all  round.  It  is  usually 
furnished  with  three  verniers,  so  as  to 
admit  of  three  distinct  readings  off",  by 
the  average  of  which  the  error  of  gra- 
duation and  of  reading  is  reduced. 

REFLECTION  (reflecto,  to  bend  back). 
In  Physics,  this  term  denotes  the  re- 
bound of  the  rays  of  light,  of  heat,  or  of 
sound,  from  an  opposing  surface.  Po- 
lished surfaces  reflect  light  to  the  eye, 
and  are,  therefore,  more  generally  termed 
reflectors  or  mirrors.  Heat  and  sound 
are  reflected  without  relation  to  the  eye, 
and  are  returned  from  more  rugged  sur- 
faces. 

Reflecting  microscopes  and  telescopes 
are  such  as  carry  a  magnified  image  of 
the  object  to  the  eye,  by  means  of  rays 
reflected  from  a  concave  speculum. 

REFRA'CTION  (refractus,  broken 
back).  That  property  of  light,  by  which 
a  ray  becomes  refracted,  or  bent  back, 
when  passing  In  an  oblique  direction 
from  a  rarer  into  a  denser  medium,  and 
vice  versd.  The  phenomenon  may  be 
observed  on  immersing  one  end  of  a  rod, 
in  a  slanting  direction,  in  a  vessel  of 
water :  the  part  immersed  appears  as  if 
it  were  bent,  or  broken,  at  the  surface 
of  the  liquid.  This  is  termed  ordinary 
refraction. 

1.  Refraction,  double.  A  property  of 
certain  transparent  minerals,  as  Iceland 
spar,  by  which  a  ray  of  light,  after  enter- 
ing such  a  medium,  becomes  divided 
into  two  portions  or  rays,  each  of  which 
presents  an  image  of  the  object.  One  of 
these  rays  follows  the  ordinary  law  of  the 
sines,  and  the  other  is  refracted  accord- 
ing to  a  new  or  extraordinary  law;  hence 
these  two  rays  have  been  termed  the 
ordinary  ray,  and  the  extraordinary  ray, 
respectively. 

2.  Refraction,  index  of.  A  term  ap- 
plied to  the  ratio  which  subsists  between 
the  sines  of  the  angles  of  incidence  and 
of  refraction,  which  is  also  in  every  case 
a  constant  ratio. 


REG 


REG 


3.  Refraction,  terrestrial  and  celestial. 
In  astronomical  and  meteorological  ob- 
servations it  is  found  that  every  differ- 
ence of  level,  accompanied,  as  it  must 
be,  with  a  difference  of  density  in  the 
aerial  strata,  must  also  have,  correspond- 
ing to  it,  a  certain  amount  of  refraction. 
That  which  occurs  between  terrestrial 
stations  is  termed  terrestrial  refraction, 
to  distinguish  it  from  that  total  effect 
which  is  produced  only  on  celestial  ob- 
jects, or  such  as  are  beyond  the  atmo- 
sphere, and  which  is  called  astronomical 
or  celestial  refraction. 

4.  Refracting  microscopes  and  telescopes 
are  such  as  show  a  magnified  image  of 
an  object,  by  means  of  rays  of  light  re- 
fracted and  collected  into  a  focus  through 
lenses. 

REFRANGIBI'LITY  {refrango,  to 
break  back).  The  property  by  which  a  ray 
of  light  admits  of  being  refracted.  The 
term  is  employed  to  designate  the  degree 
of  this  property  which  is  possessed  by 
the  several  divisions  of  a  ray  of  light. 
It  is  owing  to  their  .various  refrangibi- 
lities  that  the  rays  separate  from  each 
other  in  passing  through  the  prism, 
thereby  exhibiting  the  phenomenon  of 
the  coloured  spectrum. 

REFRIGERATION  {refrigero,  to 
cool).  The  operation  of  cooling  a  body  ; 
also  the  condition  of  a  body  which  has 
been  cooled.  A  refrigeratory  is  a  chemical 
vessel  filled  with  water,  for  the  purpose 
of  condensing  vapours,  or  for  cooling  any 
substance  as  it  passes  through  it. 

REGMA  (p^ftrtra),  to  break).  Capsula 
tricocca.  A  fruit,  consisting  of  three  or 
more  cells,  each  of  which  bursts  from  the 
axis  with  elasticity  into  two  valves,  as 
in  Euphorbia.  The  cells  of  this  kind  of 
fruit  are  called  cocci. 

REGULAR  BODIES.  A  term  ap- 
plied to  the  five  regular  geometrical 
solids,  viz.  the  tetrahedron,  the  hexa- 
hedron, the  octahedron,  the  dodecahe- 
dron, and  the  icosahedron;  these  are 
bounded  by  like,  equal,  and  regular 
plane  figures,  and  their  solid  angles  are 
all  equal.  They  were  described  by 
Plato,  and  are  hence  called  Platonic 
bodies. 

REGULAR  FIGURES.  These  are 
equilateral  and  equiangular  polygons. 
About  and  within  such  figures  circles 
can  be  described. 

RE'GULARS.  In  chronology,  there 
are  two  kinds  of  Regulars,  the  solar  and 
the  lunar. 

1.  The  Solar  Regulars  are  fixed  num- 


bers attached  to  each  month.    The  regu- 
lar for— 


April  and  July,  is |    1 

January  and  October    

2 

May 

S 

August  

4 

February,  March,  November 

5 

June | 

6 

September  and  December   ... 

7 

The  Regulars  are  used  with  the  Con- 
currents in  ascertaining  on  what  day  of 
the  week  the  first  day  of  each  month  fell. 
The  Regulars  of  the  month  being  added 
to  the  Concurrent  of  the  year,  the  sum, 
if  it  does  not  exceed  7,  shows  the  day  of 
the  week  required,  1  representing  Sun- 
day, 2  Monday,  and  so  on.  If  it  exceed 
7,  that  number  is  to  be  subtracted,  and 
the  remainder  shows  on  what  day  of  the 
week  the  first  day  of  each  month  in  that 
year  fell.  Thus,  if  the  day  of  the  week 
of  the  1st  December,  1272,  be  required: 
Regular  of  December  (7)  +  Concurrent 
of  a.  d.  1272  (5)  =12.  Subtract  7,  and 
the  remainder,  5,  denotes  the  5th  day  of 
the  week,  or  Thursday. 

2.  The  Lunar  Regulars  consist  also  of 
a  fixed  number  assigned  to  each  month 
of  the  year.  By  adding  thereto  the 
Epact,  the  age  of  the  moon  on  the  first 
day  of  each  month  is  ascertained.  The 
following  is  a  table  of  the  Lunar  Regu- 
lars, according  to  the  calculations  of 
those  who  began  the  year  in  January  or 
March :— 


1      9 

1   io 

May 

1    11 

June    

1    12 

July 

1    13 

August   

1    14 

September  and  October 

1    16 

November  and  December  ... 

1    18 

If  the  lunar  year  commenced  in  the 
month  of  September,  as  with  the  Egyp- 
tians, and  four  months  before  the  Julian 
year,  the  Lunar  Regulars  for  September 
and  October  are  5,  and  for  November  and 
December  7  ;  but  for  all  the  other  months, 
the  numbers  are  those  in  the  preceding 
table. 

By  adding  the  Lunar  Regulars  to  the 
Concurrent  of  any  particular  year,  the 
day  of  the  week  is  shown  on  which  the 
first  day  of  the  Paschal  moon  fell.  If  the 
sum  does  not  exceed  7,  the  day  following 
was  the  first  of  the  Paschal  moon ;  if  the 
Lunar  Regulars  and  Concurrent  exceed 


REP 


RET 


7,  that  number  must  be  subtracted,  and 
the  remainder  shows  that  the  next  day 
was  the  first  of  the  Paschal  moon.— Sir 
H.  Nicolas. 

RE'GULUS  {rex,  regis,  a  king).  The 
name  given  by  the  alchemists  to  the 
metallic  matters  which  were  separated 
from  other  substances  by  fusion,  from 
their  expecting  to  find  gold,  the  king  of 
metals,  at  the  bottom  of  the  crucible. 
The  term  has  since  been  applied  to  some 
metals  when  extracted  from  their  ores, 
as  regulus  of  antimony,  &c. 

RE'GULUS  (in  Astronomy).  A  star 
of  the  first  magnitude  in  the  zodiacal 
constellation  Leo.  It  is  also  called  a 
Leonis,  or  Cor  Leonis.  By  Ptolemy  and 
other  Greeks  it  was  called  (ZaoiXia-Ko?, 
whence  is  derived  the  Latin  name  Regu- 
lus, the  diminutive  of  Rex. 

RELATIVE  and  CORRELATIVE. 
The  nature  of  relative  terms  has  been 
explained  under  the  article  Absolute  and 
Relative.  Terms  are  correlative  to  each 
other,  which  denote  objects  related  to 
each  other,  and  viewed  as  in  that  rela- 
tion. Thus,  though  a  king  is  a  ruler  of 
men,  "king"  and  "man"  are  not  cor- 
relative, but  king  and  subject  are. 

REPEATING  CIRCLE.  An  astro- 
nomical instrument,  invented  by  Borda, 
by  which  the  error  of  graduation  may  be 
diminished  to  any  degree,  and,  prac- 
tically speaking,  annihilated.  By  this 
instrument  the  observer  is  enabled  to 
repeat  or  multiply  the  observation,  by 
reading  it  off  successively  on  different 
parts  of  the  graduated  limb.  A  number 
of  values  being  thus  found,  the  mean  of 
the  whole  is  taken  as  the  correct  result. 

REPETE'ND  (repetendus,  to  be  re- 
peated). The  part  of  a  circulating  deci- 
mal which  is  perpetually  repeated.  It 
is  called  simple,  when  the  figures  are  the 
same ;  and  compound,  when  they  vary. 

REPLUM.  A  leaf  of  a  door.  In  Bo- 
tany, the  framework  formed  by  the  sepa- 
ration of  the  two  sutures  of  a  legume 
from  its  valves. 

REPTATRI'CES  {repo,  to  creep). 
Creepers ;  an  order  of  Climbing  birds, 
which  have  the  three  fore  toes  more  or 
less  united  at  the  base,  and  spreading 
little.  They  are  thus  distinguished  from 
the  Scandrices,  or  Climbers,  in  which  the 
outer  toe  is  directed  outwards  or  back- 
wards. 

REPTI'LIA  {repo,  to  creep).  The 
third  class  of  Vertebrate  animals,  con- 
sisting of  reptiles,  most  of  which  are 
terrestrial.  They  are  characterized  by 
287 


cold-bloodedness,  oviparous  reproduction, 
the  absence  of  metamorphosis,  and  the 
protection  of  the  skin  by  means  of  hard 
plates  or  scales. 

REPULSION  {repello,  to  drive  back). 
That  property  of  natural  bodies,  by 
which,  under  certain  circumstances,  they 
repel,  or  fly  off*  from,  each  other,  It  is 
an  effect  of  caloric,  by  which  the  par- 
ticles of  a  body,  into  which  it  enters,  are 
removed  from  each  other.  It  is  the  op- 
posite of  that  form  of  attraction  which  is 
termed  cohesion. 

Repulsion,  in  Electricity.  The  law  by 
which  light  bodies  fly  off  from  an  elec- 
trified surface,  after  contact. 

RESI'DUAL.  An  expression  which 
gives  the  remainder  of  a  subtraction,  as 
a  —  b.  A  residual  phenomenon  is  that 
part  of  a  phenomenon  which  remains 
when  every  part  which  is  capable  of  ex- 
planation has  been  removed. 

RESIN.  A  volatile  oil,  rendered  con- 
crete by  combination  with  oxygen. 

RESISTANCE.  A  term  applied,  in 
Physics,  to  any  power  by  which  motion, 
or  a  tendency  to  motion,  is  impeded  or 
prevented.  Thus,  the  atmosphere  offers 
resistance  to  the  path  of  a  projectile,  the 
water  to  the  passage  of  a  ship,  inequality 
of  surface  to  the  movement  of  bodies  on 
one  another,  &c. 

RESOLUTION  OF  FORCES.  This 
term  denotes,  in  physics,  the  finding  of 
several  forces,  their  directions,  and  in- 
tensities, which  by  their  joint  action  have 
moved  a  body,  exactly  as  it  would  have 
been  moved  by  a  single  force  of  deter- 
minate intensity  and  direction.  See 
Force. 

RE'SONANCE  (resono,  to  sound 
again).  That  property  of  sonorous  bodies 
by  which  they  acquire  the  same  vibra- 
tions as  are  possessed  by  a  body  emitting 
a  sound;  they  thus  vibrate  with  it,  and 
strengthen  the  original  note.  A  tuning- 
fork  emits  a  louder  sound  when  its 
handle  is  placed  on  a  table  ;  the  notes  of 
a  musical  box  are  louder  when  the  box 
is  placed  upon  a  table. 

RESU'LTANT.  A  term  applied  in 
physics  to  such  a  si ngle  for ce  as  is  equi- 
valent to  the  effects  of  all  the  moving 
forces  in  any  compound  motion  ;  in  other 
words,  it  is  the  force  which  results  from 
the  composition  of  two  or  more  forces 
acting  upon  a  body.  See  Forces,  Com- 
position of. 

RETI'CULUS  RHOMBOIDA'LIS.  A 
modern  southern  constellation,  consist- 
ing of  ten  stars. 


RH  A 


RHO 


RETINA'PHTHA.  A  compound  of 
carbon  and  hydrogen,  formed  by  dropping 
resin  into  a  red-hot  cylinder. 

RE'TINITE.  Retinasphalt.  A  sub- 
stance consisting  of  resin,  asphalt,  and 
earth,  found  at  Bovey  Tracey  adhering  to 
brown  coal. 

RETITE'L^E  (rete,  a  net,  tela,  a  web). 
A  family  of  Spiders,  which  spin  webs  of 
an  open  mesh-work  and  of  an  irregular 
form,  and  remain  in  the  middle  or  on 
one  side,  in  order  to  seize  their  prey. 

RETORT.  A  globular  vessel  of  glass, 
or  porcelain,  with  a  long  neck  bended 
on  one  side,  used  for  distillation,  or  de- 
composition by  the  application  of  heat. 

RETROGRADE  {retro,  backward, 
gradior,  to  go).  A  term  used  in  Astro- 
nomy, in  opposition  to  direct.  Thus,  all 
motion  from  east  to  west,  as  the  apparent 
motion  of  the  heavens,  is  retrograde; 
while  the  earth's  diurnal  motion,  which 
causes  it,  is  direct. 

REU'SSITE.  A  substance  consisting 
of  several  sulphates,  and  occurring  in 
the  form  of  a  mealy  efflorescence  on  the 
surface  of  the  earth  about  Seidlitz  and 
Seidschutz. 

REVERBERATORY  FURNACE 
That  kind  of  furnace,  in  which  the  flame 
is  driven  back,  or  prevented  from 
rising. 

REVERSE  SHELLS.  Shells  which 
have  the  aperture  opening  on  the  left 
side  when  placed  in  front  of  the  spec- 
tator. 

REVERSION  OF  SERIES.  A  term 
sometimes  confounded,  in  Mathematics, 
with  inversion.  Thus,  the  connexion 
of  the  square  root  with  the  square  is 
described  as  inverse ;  but  if  y  be  a  given 
eeries  of  powers  of  x,  the  determination 
of  a?  in  a  series  of  functions  of  y  is  not 
called  inversion,  but  reversion. 

REVIVIFICATION  (revivisco,  to  be- 
gin to  live  again).  In  Chemistry,  this 
term  has  been  applied  to  the  reduction  of 
metals.  In  natural  history,  it  denotes  a 
phenomenon  which  occurs  in  some  ani- 
malcules, as  the  rotifer  redivivus,  which 
lives  in  water,  but,  after  remaining  for 
years  in  a  dry  state,  with  all  its  functions 
suspended,  revives  in  a  few  minutes  on 
being  placed  in  water. 

REVOLUTION.  In  pure  mathema- 
tics, this  term  denotes  an  angle  moved 
over  by  a  line  which  revolves  round  a 
point  from  any  one  position  to  that  posi- 
tion again.  It  is,  therefore,  a  synonym 
for  four  right  angles. 

RHAMNACE^E.  The  Buckthorn  tribe 


of  Dicotyledonous  plants.  Trees  or 
shrubs  with  leaves  alternate  ;  flowers  ax- 
illary or  terminal,  polypetalous  ;  petals 
cucullate ;  stamens  perigynous  ;  ovarium 
superior;  seeds  albuminous. 

RHINOLOPHI'N,E  (piv,  the  nose, 
X6(poi,  a  crest).  A  family  of  the  insec- 
tivorous Cheiroptera,  named  from  the 
peculiar  form  of  the  anterior  nasal  ap- 
pendage, and  including  the  greater  and 
lesser  horse-shoe  bats  of  our  own  coun- 
try. 

RHIPI'PTERA  (pmh,  a  fan,  mepbv, 
a  wing).  Fan-winged  insects ;  an  order 
of  insects,  which  have  only  one  pair  of 
wings  fully  developed,  and  these  are  on 
the  metathorax ;  the  other  pair  are  rudi- 
mentary.    See  Diptera. 

RHI'ZANTHS  [pifa  a  root,  &v9ov,  a 
flower).  A  class  of  parasitical  leafless 
plants,  which,  with  many  of  the  pecu- 
liarities of  Endogens,  seem  to  constitute 
an  intermediate  form  of  organization 
between  them  and  the  lower  Acrogens. 
They  are  all  of  a  fungus-like  consistence, 
with  few  traces  of  a  vascular  system  ;  the 
flowers  are  propagated  by  the  agency  of 
sexes ;  the  seeds  have  no  embryo,  but 
consist  of  a  homogeneous  sporuliferous 
mass. 

RHIZOCA'RPOUS  {pita,  a  root,  nap- 
7r6f,  fruit).  A  botanical  term  applied  to 
those  polycarpous  fruits,  whose  root  en- 
dures many  years,  but  whose  stems 
perish  annually,  as  herbaceous  plants. 

RHIZOME  {pifrna,  that  which  has 
taken  root).  A  root-stock,  or  root-like 
stem,  which  lies  prostrate  on  the  ground, 
and  emits  roots  from  its  under  side,  as 
in  iris. 

RHODIUM  {pobov,  a  rose).  A  new 
metal  discovered  in  the  ore  of  platinum, 
and  named  from  the  red  colour  of  one  of 
its  solutions. 

RHODIZONIC  ACID  (p6iov,  a  rose). 
An  acid  derived  from  carbonic  oxide,  and 
named  from  the  red  colour  of  its 
salts. 

RHO'DONITE.  A  fibrous  ore  of  man- 
ganese, consisting  of  silica  and  the  prot- 
oxide of  manganese. 

RHOMB-SPAR.  A  variety  of  man- 
ganesian  limestone,  composed  of  the  car- 
bonates of  lime  and  of  magnesia,  and 
occurring  imbedded  in  chlorite  slate, 
limestone,  &c.  It  has  been  called  bitter 
spar  and  muricalcite. 

RHOMBOID  (p6/i/3of,  a  rhombus, 
etdo?,  likeness).  A  four-sided  figure, 
which  has  its  opposite  sides  equal  to  one 
another,  but  all  its  sides  are  not  equal, 


RHY 


ROC 


nor  its  angles  right  angles.  It  is,  in 
fact,  a  compressed  parallelogram. 

In  Crystallography,  the  rhomboid,  or 
rhombohedron,  as  it  is  sometimes  called, 
is  a  figure  contained  within  six  equal 
rhombs  ;  two  only  of  its  solid  angles  are 
formed  by  the  union  of  three  equal  plane 
angles,  and  these  are  called  the  terminal 
solid  angles ;  the  other  six,  which  are 
similar  to  one  another,  are  lateral  solid 
angles.  This  form  would  result  from 
elongating  or  compressing  the  cube  in 
the  direction  of  a  line  passing  through 
two  of  its  opposite  solid  angles ;  in  the 
former  case  an  acute,  in  the  latter  an 
obtuse  rhomboid  would  result. 

RHOMBUS  {ponfios,  a  rhomb).  A 
four-sided  figure,  which  has  all  its  sides 
equal ;  but  its  angles  are  not  right 
angles;  it  is  an  equilateral  oblique  paral- 
lelogram. '?  J  | i  r 

RHUMB-LINE  {rumbo,  or  rumo,  Por- 
tuguese, a  course).  AThe  shortest  line 
which  can  join  two  points  on  the  globe, 
cutting  all  the  meridians  which  it  crosses 
at  the  same  angle ;  when  delineated  on 
the  globe,  it  forms  a  curve  termed  the 
,  loxodromic  curve. 

RHUMBS.  The  thirty-two  points  of 
the  horizon,  as  marked  on  the  circle  of 
the  mariner's  compass;  they  serve  to 
calculate  the  angle  which  a  ship's  course 
makes  with  the  magnetic  needle. 

RHUTE'NIUM.  This,  and  Plura- 
nium,  are  names  of  two  supposed 
metals,  contained  in  the  insoluble  re- 
sidue left  after  the  action  of  nitro- 
muriatic  acid  on  the  Uralian  ore  of 
platinum. 

RHY'NCHOLITHES  (ptJ-yxor,  a  beak, 
\iOos,  a  stone).  Beak-shaped  fossils ; 
the  extremities  of  the  mandibles  of  Ce- 
phalopods,  allied  to  the  nautilus. 

RHYNCHO'PHORjE  (p*ftpf,  a  muz- 
zle, (pep<a,  to  bear).  The  Weevil  tribe ; 
a  family  of  the  tetramerous  Coleoptera, 
characterized  by  the  prolongation  of  the 
anterior  part  of  the  head  into  a  kind  of 
muzzle. 

RHYNCHOS  A'URUS  (pvyX<>f,  a  beak 
travpa,  a  lizard).  A  fossil  animal  pre- 
senting certain  characters,  which  con- 
nect the  great  class  of  reptiles,  on  one 
hand  with  the  birds,  and  on  the  other 
with  quadrupeds.  The  skull  and  several 
bones  of  the  extremities  of  this  animal 
were  found  some  years  ago  in  the  Grin- 
sill  quarries,  near  Warwick. 

RHYTIDO'MA    (p,'m?,    a   wrinkle). 
The  name  given  by  Mohl  to  the  deciduous 
scales  of  the  bark  of  trees  produced  by 
289 


the  formation  of  epiphloeum  inside  the 
liber  or  mesophloeum. 

RIGEL.  A  star  of  the  first  magni- 
tude, on  the  left  foot  of  Orion. 

RIGHT  (in  Mathematics).  A  term 
generally  used  as  opposed  to  oblique.  Its 
use  may,  however,  have  arisen  from  an 
idea  of  simplicity:  a  right  line  is  a 
straight  line,  and  the  latter  has  been  de- 
fined to  be  "  the  shortest  way  between 
two  points."  A  right  angle  is  formed  by 
two  right  lines  perpendicular  to  each 
other,  and  contains  90° ;  it  is  the  most 
simple  of  angles.  A  right  cone,  cylinder, 
prism,  pyramid,  &c,  are  those  whose 
sides  are  perpendicular,  or  at  right 
angles,  to  the  plane  of  the  base. 

RINGENT  (ringo,  to  grin).  A  term 
applied  in  Botany  to  certain  corollas,  the 
petals  of  which  cohere  into  the  form  of 
a  mouth,  which  gapes  on  pressing  the 
sides,  as  in  Antirrhinum. 

RINGS,  FAIRY.  The  fanciful  name 
given  to  patches  or  to  circles  of  luxuriant 
grass,  observed  in  fields ;  they  are  sup- 
posed to  owe  their  luxuriance  to  the 
nutritive  influence  of  decaying  fungi. 

RIPPLE-MARK.  A  term  applied  by 
Geologists  to  the  undulations  which  oc- 
cur on  the  surface  of  many  rocks,  re- 
sembling the  ridges  and  indentations 
left  on  mud  and  sand  by  small  waves  of 
water.  They  are  most  distinct  on  sur- 
faces where  a  change  of  deposit  has  taken 
place,  as  where  sandstones  alternate  with 
thin  clay  partings. 

ROASTING.  A  chemical  process,  by 
which  mineral  substances  are  divided, 
some  of  their  principles  being  volatilized, 
and  others  changed,  so  as  to  prepare 
them  for  further  operations. 

ROBUR  CAROLINUM.  Royal  Oak ; 
a  modern  southern  constellation,  consist- 
ing of  twelve  stars. 

ROCK.  A  geological  term,  denoting 
the  solid  parts  of  the  crust  of  the  earth, 
formed  of  a  single  mineral  species,  or 
composed  of  two  or  more  species.  One 
or  several  rocks  united  by  certain  com- 
mon characters,  constitute  a  formation, 
or  connected  series ;  and  several  forma- 
tions constitute  a  system  of  rocks.  Rocks 
have  been  distinguished,  according  to 
peculiarities  in  their  constitution,  and  in 
their  form  and  arrangement,  into  the 
Plutonic,  the  Aqueous,  and  the  Vol- 
canic. 

1.  The  Plutonic  Rocks  are  primary  or 
primitive  in  arrangement,  igneous  in 
constitution,  and  unst ratified  in  form. 

2.  The  Aqueous  Rocks  are  secondary 

O 


ROO 


ROS 


and  tertiary  in  arrangement,  deposited 
by  water  and  stratified  in  form. 

3.  The  Volcanic  Rocks  are  of  most 
recent  arrangement,  composed  of  volcanic 
matter,  and  unstratified  in  form. 

Other  classification.  Rocks  may  be 
arranged  into  four  groups  or  classes, 
dependent  chiefly  upon  their  relative  po- 
sition. 1.  Granitic  Rock,  or  those  form- 
ing the  basis  or  foundation  of  the  rest. 
2.  Stratified  Rocks,  divided,  according  to 
the  order  of  their  deposition,  into  four 
groups,  viz.  primary,  secondary,  tertiary, 
and  alluvial.  3.  Overlying  or  interjected 
rocks,  so  named  because  they  appear  lying 
over,  or  interspersed  among,  the  stratified 
rocks.  4.  Volcanic  rocks,  of  the  same 
nature  as  the  last,  but  produced  by  vol- 
canoes at  present  or  recently  in 'action. 
The  first,  third,  and  fourth  classes  are 
all  unstratified. 

ROCK  BUTTER.  Alum  mixed  with 
alumina  and  oxide  of  iron,  oozing  out  of 
rocks  which  contain  alum. 

ROCK  CRYSTAL.  A  pure  crystal- 
lized variety  of  quartz,  of  which  the 
Scotch  cairngorm  is  a  variety.  The  pur- 
ple-coloured rock-crystals  are  commonly 
called  amethysts,  and  the  yellow-coloured 
have  the  name  of  topazes.  See  Corundum. 

ROCK  SALT.  Common  culinary  salt, 
or  chloride  of  sodium,  occurring  in  vast 
solid  masses  or  beds,  in  different  forma- 
tions, extensively  in  the  New  Red  Sand- 
stone formation,  as  in  Cheshire ;  in  this 
condition  it  is  called  rock  salt. 

ROCK  WOOD.  A  variety  of  asbestus, 
of  a  brown  colour,  and  with  the  appear- 
ance of  wood ;  found  in  the  Tyrol,  &c. 

RODE'NTIA  {rodo,  to  gnaw).  Glires. 
An  order  of  Mammalia,  in  which  the 
jaws  are  deficient  in  true  incisors,  their 
places  being  supplied  by  the  canines, 
which  are  brought  forward,  and  adapted 
to  gnawing,  as  in  the  beaver,  the  rat,  the 
hare. 

ROESTONE.  A  variety  of  compact 
limestone,  called  Bath-stone,  Ketton- 
stone,  Portland-stone,  and  Oolite;  it  is 
used  for  building,  but  is  porous  and  apt 
to  moulder  away. 

ROMA'NZOVITE.  A  species  of  gar- 
net, found  in  Finland. 

ROOT.  The  square  root  of  any  num- 
ber, as  16,  is  a  number  which,  when  mul- 
tiplied by  itself,  produces  16.  The  cube 
root  of  any  number,  as  27,  is  a  number 
which,  when  multiplied  by  itself  twice, 
produces  27.  The  fourth,  fifth,  &c.  roots 
are  numbers  which,  when  multiplied 
three,  four,  &c.  times,  produce  the  ori- 
290 


ginal  numbers.  The  mark  „J  is  the 
radical  sign,  or  sign  of  the  root,  being 
the  first  letter  of  the  Latin  term  radix, 
a  root.    Hence — 

^J  16  is  4;  for  4  x  4  =  16 

3/  27  is  3 ;  for  3  x  3  x  3  =  27 

XJ  16  is  2;  for  2  x  2  x  2  x  2=16. 

Root  of  Equation.  In  equations  the 
unknown  quantities  have  particular 
values,  which  are  sometimes  called  the 
"  roots"  of  the  equations,  and  are  said  to 
satisfy  them.  Thus,  if  #2  =  4,  we  know 
that  x  =  2  or  —  2  ;  and  2,  —  2,  are  called 
the  roots  of  the  equation  xz  =  4. 

ROOT  OF  PLANTS.  The  descend- 
ing part  of  the  axis  of  plants,  or  that 
portion  which  tends  towards  the  cen- 
tre of  the  earth.  The  main  body  is 
called  the  caudex,  its  minute  divisions 
being  called  radicles  or  fibrils.  When  a 
root  is  divided  into  many  fibrils,  it  is 
termed  a  fibrous  root ;  when  truncated  at 
the  extremity,  prcemorse ;  when  it  tapers 
conically  downward,  it  is  termed  fusi- 
form, or  tap-rooted.  Uuder  the  general 
term  root,  many  parts  have  been  erro- 
neously enumerated,  as  subterranean 
stems,  the  tuber,  the  cormus,&c. 

ROSA'CEjE.  The  Rose  tribe  of  dico- 
tyledonous plants.  Herbaceous  plants 
and  shrubs  with  leaves  alternate;  flowers 
polypetalous;  stamens  perigynous ;  ovaria 
superior,  solitary,  or  several ;  fruit  1-seed- 
ed  nuts,  or  acini,  or  follicles  containing 
several  seeds. 

ROSCHGEWACHS.  The  name  given 
by  the  Hungarian  miners  to  the  sulphur- 
salt  commonly  called  brittle  vitreous 
silver.  It  appears  to  be  composed  of  the 
same  constituent  elements  as  the  dark 
and  the  bright  red  ruby- silver  ores,  but 
in  different  proportions. 

ROSE  or  MILK  QUARTZ.  A  sub- 
species of  indivisible  quartz,  of  rose-red 
and  milk-white  colours.  It  is  probably 
silica,  coloured  with  manganese.  It  oc- 
curs in  Bavaria  in  beds  of  quartz  in 
granite. 

ROSELITE.  A  new  mineral  of  a  deep 
rose  colour,  found  on  amorphous  greyish 
quartz  in  Saxony.  It  is  an  arseniate  of 
cobalt,  with  lime  and  magnesia. 

ROSTRUM.  Literally,  a  beak;  and 
hence,  applied  in  Botany  to  any  rigid 
prolongation  of  considerable  length. 
Rostellum,  a  diminutive  of  rostrum,  is 
also  employed  to  denote  any  small  beak- 
shaped  process. 

RO'SULATE  (rosa,  a  rose).  In  bota- 
nical nomenclature,  this  term  is  used 
to  designate  parts  wli^h  are  not  oppo- 


ROT 


RUP 


posite,  but  which  nevertheless  become 
apparently  so  by  the  contraction  of  the 
joints  of  the  stem,  and  lie  packed  closely 
over  one  another,  like  the  petals  of  a 
double  rose,  the  offsets  of  houseleek,  &c. 

ROTA  MERIDIA'NA.  A  transit 
circle  erected  by  Rbmer  at  Copenhagen. 
It  was  a  divided  circle  set  upon  a  hollow 
double  cone,  at  right  angles  to  the  axis 
of  the  cones,  and  concentric  with  them, 
the  circle  being  near  one  end  of  the  axis. 
The  divisions  were  read  by  two  micro- 
scope verniers,  fixed  in  a  diameter  of  the 
circle  on  one  of  the  supports  of  the  axis. 

ROTAL  ACTION  OF  AFFINITY. 
A  term  applied  to  the  action  of  chemical 
affinity,  as  exhibited  in  the  voltaic  cir- 
cle, in  which  it  assumes  a  circular  direc- 
tion or  return  upon  itself.  It  is  what 
has  been  more  commonly  called  induc- 
tive affinity,  from  its  analogy  to  magnetic 
induction. 

ROTATE  COROLLA.  A  wheel-shaped 
corolla,  of  which  the  tube  is  very  short, 
and  the  segments  spreading,  like  the 
radii  of  a  wheel,  as  in  borago. 

ROTATION  (in  plants).  A  special 
motion  of  the  sap,  observed  in  plants  of 
low  organization.  It  consists  in  a  spe- 
cial circulation  of  the  fluid  contained  in 
the  interior  of  each  cell,  the  rotation 
in  one  cell  never  interfering  with  that 
in  another  cell.  This  phenomenon 
differs  from  that  of  cyclosis,  which  con- 
sists in  the  motion  of  the  latex  in  the 
cinenchymatous  vessels.  The  two  special 
motions  are  said  never  both  to  occur  in 
the  same  species. 

ROTATORY  MOTION  (rota,  a 
wheel).  When  the  different  points  of  a 
body  move  at  the  same  time  in  different 
directions,  this  is  called  a  rotatory  mo- 
tion, notation  on  an  axis  implies,  in 
addition  to  this  rotatory  motion,  that  all 
the  parts  of  the  body  revolve  round  an 
imaginary  right  line  in  a  state  of  rest, 
called  the  axis.  The  wheels  of  any  piece 
of  machinery  have  a  rotatory  motion 
round  their  axes  ;  the  diurnal  and  annual 
motions  of  the  earth,  a  rolling  ball,  the 
wheels  of  a  waggon  as  it  travels,  are 
illustrations  both  of  direct  and  of  rotatory 
motion. 

ROTELLI'NjE.  Wheel-shells;  a  sub- 
family of  the  Trochidcc,  named  from  the 
genus  rotella;  they  are  perlaceous,  and 
nearly  discoid  in  shape,  with  a  thickened 
mass  over  the  inner  lip. 

ROTI'FERA  (rota,  a  wheel,  fero,  to 
carry).     Infusorial   animalcules,  consist- 
ing of  minute,  transparent,  soft,  aquatic 
291 


animals,  with  distinct  muscular  and 
nervous  systems,  and  having  the  appear- 
ance of  revolving  wheels,  produced  by 
the  rapid  motion  of  the  cilia  placed  round 
the  mouth.  They  are  distinguished  into 
the  loricata,  which  have  tne  surface  of 
the  body  protected  by  a  sheath ;  and  the 
nuda,  in  which  the  body  is  soft  and 
naked. 

ROTTEN-STONE.  A  massive  mine- 
ral, consisting  of  alumina,  silica,  and 
carbonaceous  matter,  found  near  Bake- 
well,  &c,  and  employed  in  polishing 
metals. 

RUBBLE.  A  term  applied  by  quarry- 
men  to  the  upper  fragmentary  and  de- 
composed portion  of  a  mass  of  stone. 

RU'BELLITE.  Red  schorl  or  tour- 
maline, found  at  Rbzna  in  Moravia. 

RUBY.  A  crystallized  gem  of  various 
shades  of  red.  The  spinelle  ruby  is 
scarlet-coloured ;  the  balass  ruby  is  of  a 
pale  or  rose  red  ;  the  rubicelle  is  yellowish 
red.  The  oriental  ruby  of  jewellers  is 
the  red  sapphire. 

RUBY  SILVER  ORE.  A  double 
sulphur-salt;  distinguished  into  the  dark 
and  the  light  red,  both  of  the  same  crys- 
talline form,  but  in  the  latter  of  which 
sulphuret  of  arsenic  takes  the  place  of 
sulphuret  of  antimony  of  the  former. 

RUDO'LPHINE  TABLES.  A  set  of 
astronomical  tables  computed  by  Kepler, 
and  founded  on  the  observations  of  Tycho 
Brahe.  They  were  named  in  honour  of 
Rudolph  II.,  emperor  of  Bohemia,  and 
were  the  first  tables  ever  calculated  on 
the  hypothesis  that  the  planets  move  in 
elliptic  orbits. 

RUMINANTIA  (rumino,  to  chew  the 
cud).  An  order  of  the  Mammalia,  con- 
taining the  ox,  deer,  sheep,  &c,  charac- 
terized by  their  cloven  feet,  the  absence  of 
incisors  in  the  upper  jaw,  and  the  com- 
plex arrangement  of  the  stomachs  by 
which  rumination  is  effected. 

RUMINATED.  A  term  applied  to 
the  albumen  of  certain  plants,  in  which 
it  is  perforated  in  various  directions  by 
dry  cellular  tissue,  as  in  the  nutmeg,  and 
pulmaceous  plants. 

RUNNER.  A  prostrate  aerial  stem, 
forming  at  its  extremity  roots  and  a 
young  plant,  which  itself  gives  origin  to 
new  runners,  as  in  strawberry. 

RU'PTURING  or  SOLUBILITY.  In 
Botany,  the  spontaneous  contraction  of  a 
portion  of  the  pericarp,  by  which  its  tex- 
ture is  broken  through,  and  holes  formed 
for  the  dispersion  of  the  seeds,  as  in  An- 
tirrhinum and  Campanula. 
02 


SAG 


S  AI 


RUTA'CEjE.  The  Rue  tribe  of  di- 
cotyledonous plants.  Herbaceous  plants, 
with  leaves  alternate,  dotted  ;  flowers 
symmetrical;  petals  alternate  with  the 
divisions   of  the  calyx;    stamens  hypo- 


gynous ;    ovarium  entire,   celled ;   fruit 
capsular. 

RU'TILE  (rutilue,  red).  Titan-schorl. 
Native  oxide  of  titanium. 


S 


SAC  of  the  EMBRYO.  The  name 
given  by  A.  Brongniart  to  a  fifth  mem- 
brane which  sometimes  occurs  in  the 
ovule  of  plants.  Mirbel  calls  this  the 
quintine,  Malpighi  the  vesicula  amnios, 
and  R.  Brown  the  additional  membrane. 

SA'CCHARINE  MATTER  (saccha- 
rum,  sugar).  That  portion  of  vegetable 
substances  which  is  sweet  to  the  taste,  or 
which  is  capable  of  becoming  sweet 
under  certain  circumstances,  or  by  cer- 
tain manipulations.  This,  when  suffi- 
ciently fluid,  readily  enters  into  vinous 
fermentation,  emits  carbonic  acid  gas, 
becomes  of  less  specific  gravity,  and  the 
product  is  a  vinous  liquor.     See  Alcohol. 

SA'CCHAROID  (aanxap,  sugar,  eidop, 
likeness).  Saccharine.  A  term  applied 
in  Geology  to  a  stone  which  has  the  tex- 
ture of  sugar. 

SACCHARO'METER  {aaKxapov, 
sugar,  fxerpov,  a  measure).  Literally, 
a  measurer  of  sugar ;  an  instrument  em- 
ployed in  the  operations  of  brewing  and 
of  making  sugar,  its  intention  being  to 
indicate  the  density  of  the  liquid  ex- 
tracted from  malt  and  of  that  from  the 
sugar  cane.  It  acts  on  the  same  prin- 
ciple as  the  lactometer  and  the  hydro- 
meter, and  such  instruments  are  some- 
times comprehended  under  the  general 
term  arcenmeter  or  gravimeter. 

SAFETY-LAMP.  An  instrument  in- 
vented by  Davy  for  preventing  the  ex- 
plosion of  fire-damp  in  mines.  It  consists 
of  a  lamp  completely  surrounded  by  a 
cage  of  fine  wire-gauze,  through  which 
the  explosive  mixture  cannot  be  fired. 
So  soon  as  the  gas  is  inflamed  within  the 
gauze,  the  miner  is  thereby  admonished 
to  retire,  lest  the  intense  heat  of  the 
flame  should  oxidise  the  metal,  which 
would  then  fall  to  pieces. 

SAFETY-VALVE.  A  valve  fitted  to 
an  opening  in  a  boiler,  and  loaded  with  a 
weight  sufficient  to  withstand  the  elastic 
pressure  of  the  steam  until  it  rise  to  a 
certain  degree,  when  it  would  be  forced 
out,  and  thus  prevent  the  boiler  from 
bursting. 

SAGITTA.  The  Arrow;  a  northern 
292 


constellation,  consisting  of  eighteen 
stars. 

SAGITTARIUS.  The  Archer;  the 
ninth  of  the  Zodiacal  signs,  consisting  of 
69  stars.  It  denotes  the  third  month  of 
spring,  and  extends  from  the  20th  of 
May  to  the  20th  of  June.  In  the  Egyp- 
tian zodiac  the  animal  is  figured  with  the 
body  of  a  quadruped  and  with  a  double 
head,  one  of  a  lion,  the  other  of  an  armed 
man  about  to  discharge  an  arrow ;  it 
seems  to  drive  forward  the  animals  which 
precede  it,  and  to  check  those  which  fol- 
low; every  thing  indicates  that  it  will 
soon  reach  the  goal  towards  which  it  is 
tending,  and  that  its  course  is  on  the 
point  cf  terminating. 

SAH'LITE.  A  variety  of  augite,  in 
which  the  magnesia  is  only  in  part  re- 
placed by  protoxide  of  iron.  Berzelius 
calls  it  malacolite.  It  occurs  in  the  sil- 
ver mine  of  Sahla  in  Sweden. 

SAILING,  or  the  SAILINGS.  These 
terms  are  applied  to  the  different  ways  in 
which  the  path  of  a  ship  at  sea  and  the 
variations  of  its  geographical  positions 
are  represented  on  paper.  They  are  also 
occasionally  applied  to  the  rules  by 
which,  in  particular  circumstances,  a 
ship's  place  and  its  motion  are  com- 
puted. 

1.  Plane  Sailing.  This  consists  in  re- 
presenting the  line  of  a  ship's  course  or 
way,  for  a  given  time,  with  the  difference 
between  the  latitudes  and  between  the 
longitudes  of  the  two  extreme  points  of 
such  course  by  the  three  sides  of  a  right- 
angled  plane  triangle,  of  which  the  dis- 
tance actually  sailed  is  the  hypotenuse ; 
the  spaces  on  all  the  lines  being  ex- 
pressed in  nautical  miles  or  equatorial 
minutes  of  a  degree,  as  if  the  earth 
were  a  plane  surface  and  the  terres- 
trial meridians  and  parallels  of  lati- 
tude were  straight  lines  respectively 
parallel  to  each  other. 

2.  Middle-latitude  sailing.  This  term 
and  that  of  globular  sailing  have  been 
briefly  explained  in  their  alphabetical 
positions.  The  latter  is  a  general  term 
for  several  modes  of  sailing,  in  which  the 


SAI 


SAL 


rules  of  computation  are  founded  on  the 
hypothesis  that  the  earth  is  a  sphere. 

3.  Parallel  sailing.  The  term  denotes 
the  course  of  a  ship  sailing  in  a  direction 
either  due  east  or  due  west,  so  as  to  sail 
on  the  circumference  of  a  parallel  of  lati- 
tude. The  determination  of  the  ship's 
place  is  obtained  by  knowing  that,  on 
the  globe,  the  length  of  a  degree  of  a 
meridian  bears  the  same  proportion  to 
the  length  of  a  degree  of  a  parallel,  as 
the  radius  to  the  cosine  of  the  latitude 
in  which  that  parallel  is  situated. 

4.  Mercator's  sailing.  In  this  mode  of 
sailing,  the  earth's  surface  is  supposed 
to  be  projected  on  a  plane,  as  on  a  Mer- 
cator's chart  (See  Projection),  in  which 
the  meridians  and  parallels  of  latitude 
are  respectively  parallel  to  themselves. 
The  ship's  place  is  then  determined  by 
the  fact  that  the  lengths  of  infinitely 
small  portions  of  the  circumference  of  the 
equator  have  to  the  lengths  of  corre- 
sponding portions  of  a  meridian,  in  any 
latitude,  the  ratio  that  the  radius  bears 
to  the  secant  of  that  latitude. 

5.  Great-circle  sailing.  This  consists 
in  determining  a  series  of  points  in  an 
arc  of  a  great  circle  between  two  points 
on  the  surface  of  the  earth,  for  the  pur- 
pose of  directing  a  ship's  course  as  nearly 
as  possible  on  such  arc ;  that  is,  on  the 
curve  of  shortest  distance  between  the 
place  from  which  she  sets  out  and  that 
at  which  she  is  to  arrive. 

6.  Traverse  sailing.  This  is  a  general 
term  for  the  determination  of  a  single 
course  equivalent  to  a  series  of  succes- 
sive courses,  whatever  be  the  manner  of 
finding  the  lengths  of  the  lines  forming 
the  triangles. 

7.  Oblique  sailing.  This  consists  in  de- 
termining the  position  of  a  ship  by  ob- 
serving with  a  compass  the  bearings  of 
two  or  more  objects  on  the  shore,  whose 
places  are  given  on  a  chart,  and  drawing 
lines  from  those  places  so  as  to  make 
angles  with  their  meridians  equal  to  the 
observed  bearings :  the  intersection  of 
the  lines  gives  on  the  chart  the  position 
of  the  ship.  This  is  sometimes  called  the 
method  of  cross  bearings. 

8.  The  term  oblique  sailing  is  also 
applied  to  any  problem  in  which  (when 
the  triangles  are  not  right-angled)  the 
distance  of  the  ship  from  any  object  on 
the  shore,  or  of  such  objects  from  one 
another,  is  computed  by  the  rules  of 
plane  trigonometry  from  bearings  ob- 
served at  the  ship  when  the  latter  is  at 
two  or  at  a  greater  number  of  stations. 


9.  Current  sailing.  This  is  the  method 
of  determining  the  true  motion  of  a  ship 
when,  besides  being  acted  upon  by  the 
wind,  she  is  moving  in  a  current. 

10.  Windward  sailing.  A  term  applied 
to  that  mode  of  navigating  a  ship  in 
which  the  latter  endeavours  to  gain  a 
port  situated  in  the  direction  whence 
the  wind  is  blowing.  The  ship  in  this 
case  is  made,  by  frequent  tacking,  to 
sail  as  near  as  possible  to  the  wind. — 
Pen.  Cycl. 

SAL  AMMONIAC.  Salmiac.  Mu- 
riate of  ammonia.  The  native  salt  is  of 
two  kinds,  the  volcanic,  and  the  con- 
choidal ;  the  former  consisting  of  sal  am- 
moniac and  muriate  of  soda,  and  found 
in  volcanic  districts ;  the  latter  consist- 
ing of  sal  ammoniac  and  sulphate  of 
ammonia,  found,  it  is  said,  in  beds  of 
clay  slate.  Secret  sal  ammoniac  is  sul- 
phate of  ammonia,  and  was  so  named  by 
its  discoverer  Glauber. 

SAL  PRUNELLA.  Nitrate  of  potash, 
fused  and  cast  into  cakes  or  balls. 

SALAMA'NDRIDjE.  A  family  of 
Batrachians,  comprising  the  salamander, 
the  newts,  and  other  species  of  long- 
tailed  caducibranchiate  reptiles,  or  those 
which  lose  their  gills  before  they  arrive 
at  maturity,  but  retain  their  tails. 

SALICAQEjE  (salix,  the  willow).  The 
Willow  tribe  of  Dicotyledonous  plants. 
Trees  or  shrubs  with  leaves  alternate; 
flowers  achlamydeous,  amentaceous ;  ova- 
rium superior,  1  or  2-celled ;  fruit  coria- 
ceous ;  seeds  indefinite,  comose. 

SALICARIjE.  The  Loosestrife  tribe 
of  Dicotyledonous  plants.  Herbs  with 
leaves  opposite,  entire;  flowers  polype- 
talous;  calyx  tubular;  stamens  peri- 
gynous;  carpella  concrete;  and  a  su- 
perior ovarium  with  several  cells. 

SA'LICYL.  The  hypothetical  radical 
of  salicylous  and  salicylic  acids,  and 
some  other  compounds.  It  was  viewed 
by  Dumas  as  a  higher  degree  of  oxida- 
tion of  benzoyl. 

SALIENT  ANGLES  (salio,  to  jump 
or  bound  forward).  The  prominent  angles 
in  a  zigzag  line,  which  alternate  with 
the  reversed  or  re-entering  angles.  The 
term  is  frequently  used  in  fortification, 
but  seldom  in  geometry. 

SALFFEROUS  SYSTEM  {sal,  salt, 
fero,  to  bear).  A  geological  term  applied 
to  the  series  of  calcareous,  argillaceous, 
and  sandy  strata,  which  produce  rock 
salt  or  brine  springs,  and  gypsum.  The 
series  is  also  termed  New  Red  Sand- 
stone, from  the  prevalence  of  the  red 
OS 


SAL 


SAP 


colour ;  and  Poikilitic  System,  from  the 
varied  colours  of  its  rocks. 

SALIFIABLE  BASE  (sal,  a  salt,  fio, 
to  become).  A  substance  which  forms 
definite  compounds  with  an  acid,  and 
which,  when  liquid,  or  in  a  state  of  solu- 
tion, has  ah  alkaline  reaction.  The  acid, 
of  whatever  kind,  was  denominated  by 
Lavoisier,  the  salifying  principle. 

SALMO'NID^E  (salmo,  the  salmon). 
The  Salmon  and  Trout  tribe ;  a  family  of 
Malacopterygious  or  soft-spined  fishes, 
distinguished  by  the  fatty  deposition  in 
the  dorsal  fin,  from  part  of  which  the 
spines  often  disappear. 

SA'LPIANS.  An  order  of  the  tuni- 
cated  mollusca,  which  float  in  the  open 
sea,  and  are  characterized  by  their  trans- 
parent elastic  outer  tunic,  which  is  elon- 
gated, compressed,  and  open  at  both  ex- 
tremities. The  order  is  named  from  a 
kind  of  fish  called  salpe. 

SALT.  A  general  term  in  Chemistry 
for  a  combination  of  binary  compounds 
with  each  other,  as  of  sulphuric  acid 
with  soda  in  Glauber's  salt ;  such  a  com- 
bination is  called  a  ternary  compound, 
and  it  is  thus  distinguished  from  binary 
compounds,  in  which  one  element  is 
combined  with  another  element;  and 
from  quaternary  compounds,  in  which 
salts  or  double  salts,  such  as  alum,  are 
combined  together. 

1.  Nomenclature  of  Salts.  Salts  are 
named  according  to  the  acid  they  con- 
tain, the  termination  ic  of  the  acid  being 
changed  into  ate,  and  that  of  ous  into 
ite.  Thus  a  salt  of  sulphuric  acid  is  a 
sulphate;  of  sulphurous  acid,  a,  sulphite; 
&c,  and  the  name  of  the  oxide  indicates 
the  species,  as  the  sulphate  of  the  oxide 
of  silver,  or  simply  the  sulphate  of  sil- 
ver, the  oxide  of  the  metal  being  always 
understood. 

2.  A  sttper-sulphate  contains  a  greater 
proportion  of  acid  than  the  sulphate  or 
neutral  sulphate ;  a  Ji-sulphate  twice  as 
much,  and  a  sesqui- sulphate  once  and  a 
half  as  much  as  the  neutral  sulphate; 
while  a  awft-sulphate  contains  a  less  pro- 
portion than  the  neutral  salt ;  the  pre- 
fixes referring  in  all  cases  to  the  propor- 
tion of  acid  in  the  salt,  or  to  the  electro- 
negative ingredient,  as  in  the  case  of 
oxides. 

3.  The  excess  of  base  in  sub-salts  is 
sometimes  indicated  by  Greek  prefixes 
expressive  of  quantity,  as  di-chromate 
of  lead,  £r/s-acetate  of  lead ;  but  this 
deviation  from  rule  is  apt  to  lead  to  con- 
fusion.   If  a  precise  expression  for  such 

294 


sub-salts  were  required,  it  would  be 
better  to  say,  the  bibasic  subchromate  of 
lead,  the  tribasic  subacetate  of  lead. 
But  the  names  of  both  acid  and  basic 
salts  are  less  in  accordance  with  correct 
views  of  their  constitution,  than  the 
names  of  any  other  class  of  compounds. 
— Graham. 

SALT  SPRINGS.  Springs  of  water 
containing  a  large  quantity  of  common 
salt.  They  abound  in  Cheshire  and 
Worcestershire,  and  culinary  salt  is  ob- 
tained from  them  by  mere  evaporation. 

SALTATO'RES  (salto,  to  leap).  A 
family  of  Spiders  which  make  no  web, 
but  spring  upon  their  prey  by  insidious' 
and  agile  leaps. 

SALTATO'RIA  (salto,  to  leap).  A 
family  of  Orthopterous  insects,  in  which 
the  thighs  of  the  hind  legs  are  much 
larger  than  the  rest,  by  which  they  pos- 
sess great  powers  of  leaping.  They  in- 
clude the  crickets,  grasshoppers,  locusts, 
&c.     See  Cursoria. 

SALTPETRE.  Sal  petrce.  Nitre,  or 
the  nitrate  of  potash.  It  occurs  native 
as  efflorescence,  mixed  with  other  ni- 
trates, and  as  crystalline  crusts. 

SA'MARA.  The  botanical  designa- 
tion of  a  two  or  more-celled  superior 
fruit,  bordered  by  wing-like  expansions, 
as  in  sycamore. 

SAME.  This  term,  as  well  as  "  One," 
"Identical,"  and  their  derivatives,  is 
ambiguous,  and  has  led  to  much  error  in 
philosophy.  In  its  primary  sense  it  de- 
notes identity,  and  does  not  admit  of 
degrees;  in  its  secondary  sense  it  is 
employed  to  denote  great  similarity,  and, 
in  popular  usage,  admits  of  degrees,  as 
when  we  speak  of  two  things  being 
nearly  the  same,  but  not  entirely.  To 
this  ambiguity  Whately  refers  much  of 
the  error  of  Realism ;  of  Plato's  theory 
of  Ideas ;  of  the  personifications  and  dei- 
fications in  poetical  mythology ;  &c. 

SA'NDIVER.  Glass  gall.  A  saline 
substance,  which  rises  as  a  scum  in 
vessels  employed  in  the  manufacture  of 
glass. 

SANDSTONE.  Any  stone  which  is 
composed  of  agglutinated  grains  of  sand, 
whether  calcareous,  siliceous,  or  of  any 
other  mineral  nature.  The  chief  ingre- 
dient of  sand  is  granular  quartz  or  flint. 

SA'NIDINE.  Glassy  felspar;  this, 
and  ice-spar,  are  substances  nearly  allied 
to  common  felspar. 

SAP.  The  ascending  limpid  juice  of 
plants,  as  distinguished  from  the  de- 
scending or  elaborated  juice. 


SAT 


SAX 


SAPONIFICATION  {sapo,  soap,  fio, 
to  become).  The  conversion  of  any  sub- 
stance into  soap. 

SAPPHIRE.  A  variety  of  rhomboidal 
corundum,  constituting  the  ruby  and  the 
oriental  topaz. 

SA'RCOCARP  (<rap£,  o-apKor,  flesh, 
Kapnot,  fruit).  The  name  given  by 
some  botanists  to  the  parenchyma,  or 
fleshy  part  of  fruits,  lying  between  the 
epicarp  or  skin,  and  the  endocarp  or 
stone.     See  Pericarp. 

SA'RCODERM  (trap?,  crap/an,  flesh, 
dep/xa,  skin).  A  term  applied  by  De 
Candolle  to  the  substance  which  occurs 
between  the  integuments  of  the  seed, 
analogous  to  the  sarcocarp  of  fruits. 

SARCO'PHAGA  (aapt,  flesh,  0ay&>, 
to  eat).  Flesh-eating  animals  ;  a  term 
synonymous  with  the  more  usual  one 
zoophaga,  and,  like  this,  employed  in 
contradistinction  to  that  of  phy top haga. 

SARD,  or  SARDOIN.  A  variety  of 
chalcedony,  of  a  brownish  yellow  colour, 
said  to  be  found  in  Sardinia. 

SA'RDONYX.  A  variety  of  onyx,  in 
which  the  opaque  white  alternates  with 
a  rich  deep  orange  brown  of  considerable 
translucency.  The  name  is  said  to  be 
derived  from  that  of  Sardes,  in  Lydia, 
whence  the  stone  was  brought.  By 
others  it  is  referred  to  Sardo,  the  Greek 
name  of  Sardinia,  whence  the  Cartha- 
ginians are  said  to  have  exported  it. 

SARGA'SSO.  The  fucus  natans,  or 
gulf-weed,  which  is  spread  over  a  consi- 
derable part  of  the  surface  of  the  Atlantic, 
beginning  on  the  east  at  the  30th  meri- 
dian, and  extending  on  the  west  to  the 
Bahama  Islands.  Its  northern  limit  may 
be  placed  at  36°  n.  lat.,  and  its  southern 
at  19°  n.  lat.  The  abundance  of  this  weed 
has  led  to  the  Portuguese  expression  of 
Mar  de  Sargasso,  or  Weedy  Sea. 

SARME'NTUM.  The  name  given  by 
some  botanists  to  the  modification  of 
the  aerial  stem  called  a  runner. 

SAROS.  A  Chaldean  name  applied, 
according  to  some  writers,  to  an  astro- 
nomical period  of  18  years  and  10  or  11 
days,  according  as  the  18  years  have  5  or 
4  leap-years.  Berosus,  however,  speaks 
of  the '  saros  of  3600  years.  It  is,  pro- 
bably, not  a  chronological  period,  but 
only  a  portion  of  time  with  any  arbitrary 
commencement. 

SA'SSOLINE.  Native  boracic  acid, 
found  on  the  edges  of  hot  springs  near 
Sasse,  in  the  territory  of  Florence. 

SATELLITE  (safeties,  a  life-guard). 
A  secondary  planet,  or  moon,  so  named 
295 


from  its  attending  a  primary  planet,  as  a 
prince  is  attended  by  his  satellites  or 
life-guards.     See  Planet. 

SATIN  SPAR.  A  fibrous  limestone 
with  a  pearly  lustre,  from  Cumberland. 
It  consists  chiefly,  if  not  entirely,  of 
carbonate  of  lime. 

SATURATION  (saluro,  to  satisfy). 
In  the  language  of  Chemistry,  a  fluid  is 
said  to  be  saturated  with  a  substance, 
when  it  holds  as  much  of  this  substance 
in  solution  as  it  can  dissolve.  Thus, 
water  is  said  to  be  saturated  with  com- 
mon salt,  when  it  has  dissolved  about 
one-third  of  its  weight  of  the  latter :  it 
will  not  dissolve  any  more. 

Again :  when  two  principles,  which 
have  united  to  form  a  new  body,  are  in 
such  proportion  that  neither  predomi- 
nates, they  are  said  to  be  saturated  with 
each  other,  or  the  affinities  are  said  to  be 
satisfied.  If  otherwise,  the  predominant 
principle  is  said  to  be  sub-saturated,  or 
under-saturated^  and  the  other  super- 
saturated, or  over-saturated. 

SATURN.  A  planet  900  times  larger 
than  the  earth,  revolving  on  its  axis  in 
10£  hours,  and  performing  its  orbit 
round  the  sun  in  twenty-nine  years,  five 
months,  and  fourteen  days.  It  is  ac- 
companied by  eight  satellites,  and  is 
surrounded  by  two  luminous  rings. 

SAU'RIANS  (aavpa,  a  lizard).  An 
order  of  Reptiles,  in  which  the  ribs  are 
moveable,  and  there  are  one  or  two  pairs 
of  external  members.  It  comprehends 
all  the  lizard  tribe,  which  are  interr 
mediate  between  the  Loricata  and  the 
Serpents. 

SAU'ROID  FISHES  {aavpa,  a  lizard, 
etdor,  resemblance).  A  tribe  of  fishes, 
exhibiting  strong  saurian  or  reptilian 
analogies,  chiefly  in  the  teeth.  The  ex- 
isting sauroid  fishes  consist  of  seven 
species  only,  five  belonging  to  the  genus 
lepidosteus,  or  bony  pike,  and  two  species 
of  polypterus,  one  from  the  Nile,  the 
other  from  the  Niger. 

SAU'SSURITE.  Axe-stone ;  jade.  A 
mineral  found  by  Saussure  on  the  bor- 
ders of  the  lake  of  Geneva,  consisting 
principally  of  silica  and  alumina  with 
oxide  of  iron. 

SAVANNA  or  PRAIRIE.  The  name 
given  to  the  vast  plain  constituting  the 
central  part  of  North  America,  from  the 
Frozen  Ocean  to  the  Gulf  of  Mexico, 
watered  by  the  Missouri  and  the  Missis- 
sippi. This  immense  tract  of  country  is 
estimated  at  2,430,000  square  miles. 

SAXICA'VIDiE  (saxum,  a  stone,  cavo, 
04 


SCA 


SCH 


to  hollow  out).  A  family  of  the  macro- 
trachian  bivalves,  named  from  the  genus 
saxicava;  the  inhabitants  of  these  shells 
are  perforating  animals,  as  the  name 
denotes. 

SAXICOLI'NiE  (saxum,  a  stone,  colo, 
to  inhabit).  Saxicoline  birds,  or  Stone- 
chats  ;  a  family  of  the  Cantatrices  of 
Macgillivray.  Being  intimately  allied  to 
the  Turdinae,  Alaudinae,  and  Sylviinae, 
they  present  no  abrupt  and  decided  cha- 
racters by  which  they  can  be  easily  de- 
fined.   Most  of  them  are  migratory. 

SAXONY  BLUE.  An  intensely  deep 
blue,  imparted  by  dyeing  with  sulphate 
of  indigo. 

SCAGLIO'LA  {scaglia,  Ital.,  a  scale). 
An  artificial  composition  employed  for 
making  columns,  and  consisting  of  pure 
gypsum,  Flanders  glue,  isinglass,  &c. 

SCALE  {scala,  a  ladder).  A  line  di- 
vided into  a  marked  number  of  small 
and  equal  parts,  applied  as  a  measurer 
of  other  lengths  which  are  not  so  di- 
vided, in  order  to  ascertain  their  relative 
dimensions. 

Plane  diagonal  decimal  scale.  This 
instrument  consists  of  a  ruler  divided 
into  a  certain  number  of  equal  parts, 
and  these  parts,  by  a  particular  con- 
trivance, are  again  subdivided  decimally, 
or  into  tenths  and  hundredths  of  these 
parts.  By  this  instrument  we  are  en- 
abled, though  with  no  great  degree  of 
accuracy,  to  draw  lines  which  shall  bear 
to  each  other  nearly  any  proportions  we 
may  please  to  assign  them. 

SCALE  OF  NOTATION.  A  system 
of  notation  in  which  each  figure  of  a 
number  increases  its  value  in  a  certain 
proportion  in  proceeding  from  right  to 
left.  The  number,  according  to  whose 
powers  the  values  proceed,  is  called  the 
radix  of  the  scale.  This  number  is  con- 
ventional, and  there  may,  consequently, 
be  any  number  of  different  scales,  each 
of  which  has  its  own  radix.  When  the 
radix  is  2,  the  scale  is  called  binary ; 
when  3,  ternary;  when  10,  denary,  or 
decimal;  when  12,  duodenary,  or  duodeci- 
mal ;  &c. 

SCALE'NE  (<rna\nv6s,  unequal).  A 
geometrical  term  applied  to  a  triangle 
which  has  three  unequal  sides. 

SCANSO'RES  (scando,  to  climb). 
Scandrices.  Climbers ;  a  group  of  birds, 
so  named  from  their  great  facility  in 
climbing  the  branches  of  trees,  including 
the  woodpeckers,  the  cuckoos,  the  tou- 
cans, and  the  parrots.  The  external  toe 
is  turned  backward,  as  well  as  that 
296 


which  is  posterior  in  the  Rasores,  so 
that  they  have  two  posterior  and  two 
anterior  toes. 

SCAPE.  A  botanical  term  denoting 
that  form  of  inflorescence,  in  which  the 
axis  of  stemless  plants  proceeds  imme- 
diately from  the  ground,  or  near  it,  as  in 
cowslip. 

SCA'PHITE(<rKa0o?,aboat).  A  genus 
of  fossil  cephalopods,  of  a  boat-like  form. 
SCA'POLITE  (o-KciTTop,  a  rod,  XiOos,  a 
stone).  Pyramidal  felspar ;  a  substance 
now  classed  under  the  general  name 
Wernerite.  Scapolite  is  divided  by  Jame- 
son into  four  sub-species,  viz.  radiated, 
foliated,  compact  red,  and  elaolite. 

SCARABjE'IDjE  {scarabceus,  a  beetle). 
A  large  group  of  beetles  constituting  the 
principal  part  of  the  section  Lamelli- 
cornes.  They  are  distinguished  from 
the  other  section,  or  the  Lucanidcs, 
chiefly  by  the  structure  of  their  antennae, 
which  are  proportionately  shorter. 

SCA'RBROITE.  Hydrated  silicate  of 
alumina,  occurring  in  veins  in  the  beds 
of  sandstone  covering  the  calcareous 
rock  near  Scarborough,  between  septa  of 
oxide  of  iron. 

SCARI'TIDjE.  A  family  of  Coleo- 
pterous insects,  belonging  to  the  section 
Geodephaga,  and  named  from  the  genus 
scarites. 

SCELIDOTHE'RIUM  (<nce\ir,  the 
thigh,  QvpLov,  a  beast).  An  animal  of 
the  megatheroid  type,  exhibiting  a  tran- 
sition to  the  ant-eater  and  armadillo, 
which  it  resembles  more  than  the  sloth 
in  the  form  and  structure  of  the  skull. 

SCHAALEN  BLENDE.  Testaceous 
blende;  a  sulphuret  of  zinc,  containing 
iron  and  lead.  The  most  characteristic 
specimens  are  found  at  Geroldseck  in  the 
Brisgau. 

SCHAALSTEIN.  Tabular  spar  or 
table  spar;  a  silicate  of  lime,  occurring 
in  primitive  rocks,  where  it  is  associated 
with  brown  garnets.  This  is  the  pris- 
matic augite  of  Jameson. 

SCHAUM  EARTH.  Aphrite,  or 
earth  foam;  a  carbonate  of  lime,  oc- 
curring usually  in  a  friable,  but  some- 
times in  a  solid  state,  with  a  shining 
lustre,  between  semi-metallic  and  pearly. 
SCHEAT.  A  star  of  the  third  magni- 
tude in  the  constellation  Aquarius. 

SCHEELE'S  GREEN.  Arsenite  of 
copper ;  a  green  pigment. 

SCHEE'LIUM.  Pyramidal  tungsten ; 
an  ore  of  tungsten,  named  from  Scheele, 
its  discoverer.  Scheelite  is  a  tungstate 
of  lime;  scheel-lead  ore,  a  tungstate  of 


SCH 


SCL 


lead,  formerly  confounded  with  the  mo- 
lybdate  of  this  metal. 

SCHELLING'S  PHILOSOPHY.  A 
system  of  philosophy,  which  teaches  the 
identity,  or  indifference,  of  the  ideal  and 
the  real.  It  was  propounded  by  Schel- 
ling  about  thirty  years  ago,  and  appears 
to  be  directly  opposed  to  the  philosophy 
of  Kant. 

SCHERBEN  COBALT.  Testaceous 
cobalt.  Names  formerly  given  to  native 
arsenic.  It  occurs  in  reniform  and  bo- 
tryoidal  shapes  at  Andreasburg,  &c. 

SCHE'RERITE.  A  species  of  com- 
bustible mineral  found  in  a  bed  of  brown 
coal  in  Switzerland.  It  seems  to  be  a 
mineral  naphthaline  :  its  constituents 
are,  hydrogen,  24 ;  carbon,  73. 

SCHIEFER  SPAR.  Slate  spar.  A 
sub-species  of  limestone,  also  called 
foliated  carbonate  of  lime. 

SCHILLER  SPAR.  A  mineral  sub- 
stance, constituting  a  variety  of  asbes- 
tine ;  it  is  also  called  metalloid  diallage 
or  diallagite.  It  contains  two  sub-species, 
viz.,  bronzite  and  common  schiller  spar. 
The  term  is  derived  from  the  German 
schillern,  to  change  colours,  and  indi- 
cates the  changeable  hues  of  the  mi- 
neral. 

SCHIST  (schistus,  that  which  may  be 
split).  A  term  often  used  synonymously 
with  slate ;  but  it  may  be  very  useful  to 
distinguish  between  a  schistose  and  a 
slaty  structure.  The  hypogene  or  pri- 
mary schists,  as  they  are  termed— as 
gneiss,  mica-schist,  and  others — cannot 
be  split  into  an  indefinite  number  of 
parallel  laminae,  like  rocks  which  have  a 
true  slaty  cleavage.  The  uneven  schist- 
ose layers  of  mica-schist  and  gneiss  are 
probably  layers  of  deposit  which  have 
assumed  a  crystalline  texture. 

SCHISTOSE  ROCKS.  Rocks  which 
have  the  character  of  schist.  See  Schist. 
SCHI'ZOPODS  (<T-x'£«>.  to  cleave,  now, 
a  foot).  A  tribe  of  long-tailed  decapod 
crustaceans,  the  legs  of  which  are  accom- 
panied by  an  external  articulated  branch 
as  long  as  the  limbs,  which  thus  appear 
double  in  number.  The  mysis,  or  opos- 
sum shrimp,  is  an  illustration  of  the 
tribe. 

SCHMELZSTEIN.  Another  name  for 
dipyre,  under  which  name  the  characters 
of  this  mineral  are  noticed. 

SCHO'LIUM  {oxokiov,  a  comment). 
A  remark  or  observation.  In  Geometry, 
a  scholium  is  a  note  or  observation  on  a 
proposition  not  containing  any  infer- 
ence, or,  at  least,  none  of  sufficient 
297 


importance  to  entitle  it  to  the  name  of 
corollary. 

SCHORL  (scorl,  Swed.,  brittle).  Com- 
mon schorl  is  a  sub-species  of  rhom- 
boidal  tourmaline,  consisting  chiefly  of 
silica,  alumina,  and  oxide  of  iron,  and 
occurring  imbedded  in  granite,  gneiss, 
&c.  Blue  schorl  is  a  variety  of  Haiiyne. 
Red  and  Titanitic  schorl  are  name3  of 
rutile,  an  ore  of  titanium.  Schorl  rock  or 
schorly  granite  is  a  rock,  in  which  crystals 
of  schorl  are  added  to  the  usual  ingre- 
dients of  granite ;  or  when  quartz  and 
schorl  only  occur,  the  felspar  and  mica 
having  disappeared. 

SCHORLITE,  or  SCHORLOUS  TO- 
PAZ. Pycnite  of  Werner.  A  mineral 
consisting  of  alumina,  silica,  and  fluoric 
acid,  occurring  at  Altenberg  in  Saxony, 
in  a  rock  of  quartz  and  mica  in  porphyry. 

SCHRIFTERTZ.  Graphic  tellurium; 
a  combination  of  tellurium  with  silver 
and  gold. 

SCIiENOIDS.  A  family  of  acan- 
thopterygian  fishes,  nearly  allied  to  the 
Percoids,  and   named  from    the  genus 


SCIjENU'RUS.  A  genus  of  fossil 
fishes,  representing  the  perch  and  other 
allied  forms.  Its  remains  are  very  com- 
mon in  the  London  clay  of  Sheppey. 

SCIENCE  {scientia,  knowledge).  This 
term,  in  its  most  comprehensive  sense, 
only  means  knowledge;  in  its  ordinary 
sense  it  denotes  knowledge  reduced  to  a 
system;  that  is,  arranged  in  a  regular 
order,  so  as  to  be  conveniently  taught, 
easily  remembered,  and  readily  applied. 

SCINCO'IDiE.  The  Skink  tribe,  or 
Serpent  Lizards;  a  family  of  Saurian 
reptiles,  characterized  by  the  shortness 
of  their  feet,  the  roundness  of  their  body, 
and  the  equality  of  the  tile-like  scales 
with  which  their  body  is  covered. 

SCITAMINEiE.  The  Ginger  tribe  of 
monocotyledonous  plants.  Herbaceous 
plants  with  a  creeping,  often -jointed, 
rhizome;  leaves  simple,  sheathing; 
flowers  tripetaloideous ;  stamens  3,  dis- 
tinct; ovarium  3  celled ;  fruit  capsular, 
3-celled,  many-seeded:  seeds  with  or 
without  an  arillus. 

SCIU'RIDiE  (aiciovpos,  a  squirrel; 
from  ama,  shade,  and  ovpa,  a  tail).  The 
Squirrel  tribe ;  a  family  of  the  Rodentia, 
comprising  the  squirrels,  marmots,  dor- 
mice, &c,  characterized  by  long,  bushy 
tails,  and  their  adaptation  to  a  residence 
in  trees. 

SCLERODE'RMI  ( <nc\»,p6r,  hard, 
depua,  skin).  A  family  of  Plectognathous 
05 


SCR 

fishes,  characterized  hy  their  very  hard 
and  granulated  skins.  The  roughness  of 
the  skin  in  some  of  the  species  has  sug- 
gested the  common  term  of  file-fishes. 

SCLE'ROGEN  (c-KXrjpop,  hard,  yevvdw, 
to  produce).  The  matter  of  lignification 
which  is  deposited  on  the  inner  surface 
of  the  cells  of  plants,  contributing  to 
their  thickness. 

SCO'LIADjE.  A  family  of  fossorial 
hymenopterous  insects,  named  from  the 
genus  scolia. 

SCOLOPA'CIDjE  (scolopax,  the  wood- 
cock). The  Snipe  tribe  ;  a  family  of  the 
Grallatores,  or  Wading  birds,  charac- 
terized by  their  long,  slender,  and  feeble 
bill. 

SCOLYMI'NiE.  A  sub-family  of  the 
Turbinellidce,  or  Turnip-shells,  named 
from  the  typical  genus  scolymus,  and 
characterized  by  a  ponderous  and  rough 
shell,  with  foliated  spines  or  tubercles. 

SCOMBE'RIDjE  {scomber,  the  mack- 
erel). The  Mackerel  tribe ;  a  family  of 
the  Acanthopteryginus  or  spiny-finned 
fishes,  including  the  mackerel,  tunny, 
sword-fish,  dory,  dolphin,  &c. 

SCO'PIPEDS  [scopce,  a  brush,  pes,  a 
foot).  A  tribe  of  melliferous  insects,  in- 
cluding those  which  have  the  tarsi  of 
the  posterior  feet  furnished  with  a  brush 
of  hairs. 

SCORIAE  (oKiapla,  from  o-Kcbp,  excre- 
ment). The  scum  or  dross  of  metals ; 
the  refuse  or  useless  part  of  any  sub- 
stance ;  volcanic  cinders  ;  &c. 

SCO'RPIO.  The  Scorpion  ;  the  eighth 
of  the  zodiacal  constellations,  consisting 
of  forty-four  stars,  the  principal  of  which 
is  Antares.,  It  denotes  the  second  month 
of  spring,  extending  from  the  20th  of 
April  to  the  20th  of  May.  The  heat  of 
this  month  stimulates  venomous  rep- 
tiles, and  excites  disease  and  pesti- 
lence. 

SCREW.  One  of  the  mechanical 
powers.  It  may  be  considered  as  an  in- 
clined plane  wrapped  round  a  cylinder, 
or  as  a  cylinder  having  on  its  surface  a 
projecting  thread  inclined  in  all  parts  at 
the  same  given  angle  to  the  horizon. 
The  cylinder  fits  into  a  block  pierced 
with  an  equal  cylindrical  aperture,  on 
the  inner  surface  of  which  is  cut  a 
groove,  the  exact  counterpart  of  the 
thread  on  the  screw;  hence  we  can 
cause  the  screw  to  enter  the  block  by 
merely  making  it  revolve  about  its 
axis. 

Endless  Screw.  The  force  of  the  screw 
is  sometimes  employed  to  turn  a  wheel, 


SEA 

by  acting  on  its  teeth,  the  thread  of  the 
screw  passing  between  the  teeth  or  cogs 
of  the  wheel.  In  this  case  it  is  called  a 
perpetual  or  endless  screw. 

SCROPHULARIA'CE^E.  The  Fig- 
wort  tribe  of  Dicotyledonous  plants. 
Herbaceous  plants  with  leaves  opposite  ; 
flowers  irregular,  unsymmetrical ;  sta- 
mens 2  or  4,  didynamous ;  fruit  capsular; 
seeds  albuminous. 

SCURF  OF  PLANTS.  A  term  ap- 
plied in  Botany  to  the  thin,  flat,  mem- 
branous disks,  with  a  ragged  margin, 
formed  of  cellular  tissue,  springing  from 
the  epidermis  of  plants.  They  are  dis- 
tinguished into  scurf,  properly  so  called, 
and  ramenta. 

SCUTE'LLUM  (dim.  of  scutum,  a 
shield).  Apothecium.  The  botanical  de- 
signation of  the  little  coloured  cup  or 
disk,  found  in  the  substance  of  lichens  ; 
it  is  surrounded  by  a  rim,  and  con- 
tains the  asci,  or  tubes  filled  with  spo- 
rules. 

SCUTIBRANCHIA'TA  {scutum,  a 
shield,  branchice,  gills).  An  order  of 
gasteropods  which  have  pectinated  gills 
disposed  in  a  special  cavity,  with  shells 
which  are  very  wide,  scarcely  ever  turbi- 
nated, and  cover  the  body  and  gills, 
like  a  shield. 

SCU'TIPEDS  {scutum,  a  shield,  pes,  a 
foot).  The  name  given  by  Scopoli  to 
those  birds  which  have  the  anterior  part 
of  the  leg  covered  with  segments  of  un- 
equal horny  rings  terminating  on  each 
side  in  a  groove. 

SCUTUM  SOBIESKI.  Sobieski's 
shield ;  a  modern  northern  constella- 
tion, consisting  of  eight  stars. 

SCYLLA'RIANS.  A  tribe  of  macru- 
rous  decapods,  established  by  Milne 
Edwards  on  the  genus  scyllarus  of  Fa- 
bricius,  and  forming  one  of  the  most  re- 
markable groups,  distinguished  at  the 
first  glance  by  the  singular  conformation 
of  the  external  antennae.  It  comprises 
the  genera  Scyllarus,  Thenus,  and  Iba- 
cus. 

SEA.  A  portion  of  the  ocean  which 
penetrates  into  a  continent  by  a  narrow 
passage,  and  then  spreads  into  a  large 
expanse,  as  the  Mediterranean  sea.  The 
term  is,  however,  frequently  employed 
in  a  larger  sense  to  denote  the  whole 
volume  of  water  which  occupies  the 
lower  portion  of  the  surface  of  our  globe, 
or  three-fourths  of  its  entire  superficies ; 
in  this  sense  it  is  synonymous  with 
ocean. 
SEA  WAX.    Maltha;  a  white,  solid, 


SEC 


SEE 


waxy-looking  fusible  substance,  found  on 
the  Baikal  lake  in  Siberia. 

SEAMS.  Thin  layers  which  separate 
two  strata  of  greater  magnitude. 

SEASONS  OF  THE  YEAR.  The 
four  quarters  of  the  year,  commencing, — 
the  first,  or  Spring  quarter,  when  the 
sun  enters  Aries ;  the  second,  or  Sum- 
mer, when  he  enters  Cancer ;  the  third, 
or  Autumn,  when  he  enters  Libra;  the 
fourth,  or  Winter,  when  he  enters  Capri- 
corn. The  variety  of  the  seasons  de- 
pends on  the  uniform  direction  of  the 
axis  of  the  earth  ;  this  is  always  carried 
round  parallel  to  itself,  and  pointing 
always  to  the  same  vanishing  point  in 
the  sphere  of  the  fixed  stars. 

SEBA'CIC  ACID  {sebum,  lard).  An 
acid  obtained  from  the  oleic,  or  from  any 
of  the  fats  which  contain  this  acid.  Its 
salts  are  called  sebates. 

SECANT  (seco,  to  cut).  A  line  which 
cuts  another  line.  In  trigonometry,  it  is 
a  straight  line  drawn  from  the  centre  of 
a  circle  to  one  extremity  of  an  arc,  and 
produced  until  it  meets  the  tangent  to 
the  other  extremity.  The  secant  of  an 
arc  is  a  third  proportional  to  the  cosine 
and  the  radius  ;  hence,  if  the  radius  be 
taken  as  unity,  the  secant  is  the  recipro- 
cal of  the  cosine.     See  Trigonometry. 

SECOND.  The  sixtieth  part  of  a 
minute,  in  calculations  either  of  time  or 
of  angular  measure.    See  Hour. 

SECOND  (in  Music).  An  interval 
producing  a  discord,  the  rartio  of  which 
is  9  J  8.  There  are  three  kinds  of  second, 
the  minor  or  semitone,  as  EF;  the 
major,  or  CD;  and  the  extreme  sharp 
second,  as  CD  ft. 

SECONDARIES.  Secondary  circles. 
In  Astronomy,  all  those  circles  on  the 
sphere  which  intersect  a  primary  circle 
at  right  angles,  passing  through  the  axis 
and  the  poles,  are  called  secondaries. 

SECONDARY  STRATA.  An  exten- 
sive series  of  the  stratified  rocks  which 
compose  the  crust  of  the  globe,  with  cer- 
tain characters  in  common,  which  distin- 
guish them  from  another  series  below 
them  called  primary,  and  from  a  third 
series  above  them  called  tertiary. 

SECRETION  (secernn,  to  separate). 
A  general  term  for  that  function  in  ani- 
mal and  vegetable  physiology,  by  which 
certain  products  are  secreted  or  separated 
from  the  circulating  fluid,  —  from  the 
blood  in  animals,  from  the  sap  in  plants. 
The  same  term  is  also  applied  to  the 
products  so  secreted  or  separated.  Thus, 
the  liver  secretes  bile,  and  bile  is  called 
299 


the  secretion  of  the  liver;  the  tuber 
secretes  starch,  and  this  is  termed  a 
secretion  of  the  tuber. 

SECTOR  (seco,  to  cut).  A  sector  of  a 
circle  is  the  figure  contained  by  two  radii 
and  the  arc  between  them  ;  it  thus  differs 
from  a  segment,  which  is  included  by  an 
arc  and  its  chord.  A  sector  with  a  right 
angle  is  a  fourth  part  of  a  circle,  and  its 
arc  is  called  a  "  quadrant."  The  term 
sector  is  also  applied  to  a  mathematical 
instrument,  the  purpose  of  which  is  to 
facilitate  the  graphical  determination 
of  proportional  quantities;  hence  it  is 
termed  by  the  French  the  compass  of 
proportion. 

SECTOR,  ZENITH.  A  peculiar  mo- 
dification of  the  altitude  and  azimuth 
instrument.  It  is  adapted  for  the  very 
exact  observation  of  stars  in  or  near  the 
zenith,  by  giving  a  great  length  to  the 
vertical  axis,  and  suppressing  all  the 
circumference  of  the  vertical  circle,  ex- 
cept a  few  degrees  of  its  lower  part,  by 
which  a  great  length  of  radius,  and  a 
consequent  proportional  enlargement  of 
the  divisions  of  its  arc,  are  obtained. 

SECULAR  and  PERIODIC.  In 
Astronomy,  any  deviation  from  the  mean 
motion  or  mean  orbit  of  a  celestial  body 
is  called  an  inequality,  and  the  numeri- 
cal expression  of  the  magnitude  and 
period  of  the  inequality  is  called  an 
equation.  An  equation  of  this  kind  is 
said  to  be  periodic,  when  the  motions  it 
expresses  perform  their  changes  in  a 
comparatively  short  period  of  time  ;  secu- 
lar, when  the  changes  are  so  gradual  as 
to  be  insensible  only  after  the  lapse  of 
centuries.  Thus,  the  lunar  evection  is  a 
periodic,  the  acceleration  of  the  moon's 
mean  motion,  a  secular  inequality. 

SECULAR  REFRIGERATION  (sa:- 
culum,  an  age).  The  periodical  cooling 
and  consolidation  of  the  globe  from  a 
supposed  original  state  of  fluidity  from 
heat. 

SECUNDINE.  The  name  given  by 
botanists  to  that  sac  of  the  ovule  which 
reposes  immediately  upon  the  primine, 
and  often  contracts  an  adhesion  with  it, 
so  that  the  two  integuments  become  con- 
founded. Its  point  is  usually  protruded 
beyond  the  foramen  of  the  primine. 

SEDIMENTARY  ROCKS.  Rocks 
which  have  been  formed  by  their  mate- 
rials having  been  thrown  down  from  a 
state  of  suspension  or  solution  in  water. 

SEED  OF  PLANTS.  The  seed  of  a 
plant  is  the  ovule  in  its  matured  state  ; 
it  is  then  a  body,  enclosed  in  a  pericarp, 
06 


SEM 


SEP 


clothed  with  its  own  integuments,  and 
containing  the  rudiment  of  a  future 
plant.  It  is  the  point  of  development  at 
which  vegetation  stops,  and  beyond  which 
no  increase,  in  the  same  direction  with 
itself,  can  take  place. 

SEGMENT  (seco,  to  cut).  That  part 
of  a  circle  which  is  contained  by  a 
straight  line  and  the  circumference  it 
cuts  off.  1.  The  angle  of  a  segment  is 
that  which  is  contained  by  the  straight 
line  and  the  circumference.  2.  An  angle 
in  a  segment  is  the  angle  contained  by 
two  straight  lines  drawn  from  any  point 
in  the  circumference  of  the  segment  to 
the  extremities  of  the  straight  line  which 
is  the  base  of  the  segment.  3.  Similar 
segments  of  a  circle  are  those  in  which 
the  angles  are  equal,  or  which  contain 
equal  angles. 

SELA'CHII.  The  Shark  and  Ray 
tribe;  an  order  of  Chondropterygious  or 
cartilaginous  fishes,  distinguished  by  the 
peculiar  conformation  of  the  mouth,  the 
jaws  not  being  united  into  a  ring,  and 
the  true  jaw-bones  not  being  developed. 
Several  of  the  species  are  viviparous. 

SE'LENITE  {(Te\f]vt),  the  moon). 
Sparry  gypsum.  A  simple  mineral,  con- 
sisting of  pure  gypsum,  or  sulphate  of 
lime. 

SELENIUM  {<re\t]vn,  the  moon).  A 
metal  discovered  in  the  sulphur  of  Fah- 
lun,  and  named  from  its  strong  analogy 
to  another  metal,  tellurium,  which  is 
named  from  tellus,  the  earth.  It  com- 
bines with  oxygen,  forming  the  selenious 
and  selenic  acids. 

SEMI-.  A  Latin  prefix,  derived  from 
semis,  half,  and  corresponding  with  the 
term  hemi  in  Greek  compounds. 

1.  Semi-amplexicaul.  Half  stem-em- 
bracing ;  as  applied  to  the  leaves  of  plants 
which  partially  sheath  the  stem. 

2.  Semi-anatropous.  A  term  denoting 
the  same  as  amphitropous,  except  that  in 
the  former  the  ovule  is  parallel  with  the 
funiculus,  while  in  the  latter  it  is  at 
right  angles  with  it. 

3.  Semi-circle.  Half  a  circle ;  a  figure 
contained  by  a  diameter  of  a  circle,  and 
the  portion  of  the  circumference  cut  off 
by  the  diameter. 

4.  Semi-diameter.  Half  a  diameter,  or 
a  right  line  drawn  from  the  centre  of  a 
circle,  or  sphere,  to  its  circumference  ;  it 
is  otherwise  called  a  radius. 

5.  Semi-flosculous.  A  term  applied  to 
the  ligulate,  or  strap-shaped,  florets  of 
some  of  the  compositae,  as  of  dandelion ; 
in  this  and  similar  plants,  the  limbs  of 

300 


the  cohering  petals  are  united  on  one 
side  of  the  floret,  giving  it  the  appear- 
ance of  half  a  floret. 

6.  Semi-metals.  A  term  formerly  ap- 
plied to  those  bodies  which  possess  the 
qualities  of  metals,  with  the  exception 
of  malleability. 

7.  Semi- opal.  A  variety  of  opal,  of 
white,  grey,  and  brown  colours ;  some- 
times in  spotted,  striped,  or  clouded  deli- 
neations ;  occurring  in  porphyry  and 
amygdaloid. 

8.  Semi-quadrate  or  semi-quartile.  An 
astrological  term  denoting  an  aspect  of 
the  planets  when  distant  from  one  an- 
other half  a  right  angle,  or  45°.  The 
terms  semi-quartile  and  semi-sextile  have 
similar  meanings,  the  former  denoting 
the  half  of  a  fifth  of  the  complete  circle, 
or  36°,  the  latter  the  half  of  a  sixth,  or 
30°. 

9.  Semi-tone.  An  interval  in  music 
whose  ratio  is  16  \  15,  as  CC  %  It  can- 
not correctly  be  called  half  a  tone,  as 
there  are  different  kinds  of  semitones, 
greater,  lesser,  and  natural. 

SENECTI'N^.  Sea-snails  ;  a  sub- 
family of  the  Trochidce,  named  from  the 
genus  senectus,  resembling  the  garden 
snail  in  form,  but  perlaceous,  and  fur- 
nished with  a  thick,  round,  fleshy  oper- 
culum. 

SEN'SIBLE  (sentio,  to  perceive).  A 
vague  term  applied  indifferently  to  a 
body  capable  of  receiving,  of  producing, 
or  of  conducting  sensation.  It  has  been 
suggested  that  the  term  sentient  should 
be  applied  to  the  first  of  these  cases,  and 
sensitive  to  the  third.  In  the  fourth  and 
most  ordinary  acceptation  of  the  word 
sensible,  it  is  used  to  express  the  state 
of  the  intellectual  powers. 

SE'PAL.  The  botanical  designation 
of  each  of  the  leaves  composing  the 
calyx,  or  external  envelope  of  the  floral 
apparatus.  When  the  leaves  are  distinct 
from  one  another,  the  calyx  is  termed 
poly-sepalous ;  whe  i  they  cohere,  it 
is  called  gamosepalous,  or,  incorrectly 
though  popularly,  mono-sepalous.  A  se- 
pal may  be  hollowed  out  into  a  conical 
tube,  as  in  larkspur,  and  is  then  said  to 
be  spurred. 

SE'PIADjE  (sepia,  the  cuttle-fish).  A 
family  of  cephalopods,  vulgarly  known 
as  cuttle-fish  ,  and  divisible  into  two 
groups,  the  octopods  and  the  decapods. 

SEPTA'RIA  {septum,  a  division).  Lu- 
di  Helmontii.  Flattened  balls  of  stone, 
generally  a  kind  of  iron-stone,  which,  on 
being  split,  are  found  to  be  separate  i  in 


SER 


SES 


their  interior  into  irregular  masses. 
From  these  septaria  is  manufactured  the 
material  for  building  under  water,  known 
as  Parker's  or  Roman  cement. 

SEPTICI'DAL  {septum,  a  division, 
ccedo,  to  cut).  That  kind  of  dehiscence 
of  fruits,  in  which  the  septa  separate 
each  into  two  laminae,  as  in  rhododen- 
dron. Formerly,  botanists  used  to  say 
that  in  this  sort  of  dehiscence  the  valves 
were  alternate  with  the  dissepiments,  or 
that  the  valves  had  their  margins  turned 
inwards. 

SEPTI'FRAGAL  {septum,  a  division, 
frango,  to  break).  That  kind  of  de- 
hiscence of  fruits,  in  which  the  backs  of 
the  carpels  separate  from  the  septa, 
which  adhere  to  the  axis,  as  in  convol- 
vulus. 

SERIES.  In  Mathematics,  a  series  is  a 
set  of  terms,  finite  or  infinite  in  number, 
connected  together  by  addition  or  sub- 
traction, and  formed  upon  some  distinct 
law.  An  arithmetical  series  is  one  in 
which  each  term  differs  from  the  preced- 
ing by  the  addition  or  subtraction  of  a 
constant  number  or  quantity;  a  geome- 
trical series  is  one  in  which  each  term  is 
a  multiple  of  the  preceding  by  a  con- 
stant factor. 

1.  Series,  infinite.  A  series  of  terms 
proceeding  according  to  some  law,  and 
continued  without  limit.  The  sum  of  an 
infinite  series  is  the  limit  to  which  we 
approach  more  nearly  by  adding  more 
terms,  but  which  cannot  be  exceeded  by 
adding  any  number  of  terms  whatever. 

2.  A  convergent  series  is  one  which  has 
a  sum  or  limit,  as  above  defined  ;  a  di- 
vergent series  is  one  which  has  no  such 
sum  or  limit.  Hence,  every  infinite 
series  in  Geometrical  progression,  in 
which  the  common  ratio  is  less  than  I, 
is  convergent. 

3.  Series,  recurring.  If  each  succeed- 
ing term  of  a  decreasing  infinite  series 
bear  an  invariable  relation  to  a  certain 
number  of  the  preceding  terms,  the 
series  is  called  a  Recurring  Series,  and 
its  sum  may  be  found.  Thus  a  +  {a  +  1) 
x  +  (2  a  +  2)  a;2  +  (3a  +  3)  a*  +  (5a  +  5) 
x*  +  .  . .  is  a  recurring  series,  the  co- 
efficient of  each  term  being  the  sum  of 
the  co-efficients  of  the  two  preceding 
terms. 

4.  An  exponential  series  is  one  whose 
terms  depend  on  exponential  quantities  ; 
a  logarithmic  series  is  one  whose  terms 
depend  on  logarithms ;  and  a  circular 
series,  one  whose  terms  depend  on  cir- 
cular functions,  as  sines,  co- sines,  &c. 

301 


5.  The  general  term  of  a  series  is  a 
function  of  some  indeterminate  quan- 
tity x,  which,  on  substituting  succes- 
sively the  numbers  1,  2,  3,  &c,  for  ar, 
produces  the  terms  of  the  series. 

SERPENS.  A  northern  constellation, 
consisting  of  sixty-four  stars.  Mytho- 
logically,  it  is  the  serpent  carried  by  Ser- 
pentarius,  the  serpent-bearer. 

SERPENTARIUS.  Ophiuchus.  A 
northern  constellation,  containing  se- 
venty-four stars,  the  principal  of  which 
is  Ras  Aliagus. 

SER'PENTINE.  A  rock  of  the  pri- 
mary series,  closely  related  to  diallage 
rock,  of  irregular  form  and  of  various 
colours :  when  opaque,  it  is  named  com- 
mon serpentine ;  when  translucent, 
noble  or  precious  serpentine.  It  con- 
sists of  hydrate  of  magnesia  with  sub- 
silicate  of  magnesia.  The  name  is  de- 
rived from  its  frequent  contrasts  of 
colour,  like  those  of  the  skin  of  some 
serpents. 

SERPU'LEANS.  A  family  of  cepha- 
lobranchiate  annellides,  inhabiting  cylin- 
drical and  tortuous  calcareous  tubes; 
generally  parasitic  on  shells. 

SERRICORNES  {serra,  a  saw,  cornu, 
a  horn).  A  family  of  the  pentamerous 
coleoptera,  distinguished  by  the  serrated 
or  toothed  form  of  the  antennae.  They 
have  four  palpi,  and  the  body  is  com- 
pletely covered  by  the  elytra,  or  wing- 
cases. 

SE'RTULUM.  A  term  applied  by 
some  botanists  to  the  simple  umbel,  the 
latter  term  being  by  them  restricted  to 
the  compound  form  of  this  inflorescence. 

SESQUI-  (contracted  from  semisque, 
and  a  half).  A  prefix  to  certain  words, 
denoting  so  much  and  half  so  much,  the 
whole  of  a  thing  and  a  half  more.  It  is 
used  in  chemical  language  when  the  ele- 
ments of  an  oxide  are  as  1  to  l£,  or  as 
2  to  3.  The  sulphurets,  carburets,  &c, 
of  the  same  substance  are  similarly  de- 
signated. Hence,  also,  the  word  sescu- 
plum  (quasi  sesqui-plum,  from  sesqui  and 
plica,  a  fold) ;  thus  sescuplo-carburet, 
one  and  a  half-fold  carburet. 

Sesqui-duplicate.  A  term  sometimes 
found  in  treatises  on  Geometry,  signifying 
the  ratio  in  which  the  greater  term  is 
twice  and  a  half  times  the  less ;  as  the 
ratio  of  10  to  4;  of  15  to  6 ;  &c. 

SESSILE  {sessilis,  sitting).  Destitute 
of  any  support  or  peduncle,  as  a  leaf 
which  has  no  stalk,  or  the  shell  of  the 
anomia.  The  term  Sessiles  has  been 
adopted  for  a  division  of  the  Cirrhopoda, 


SH  A 


S  ID 


comprehending  those  species  which  are 
not  suspended  by  a  pedicle. 

SET  OF  CURRENT.  The  direction 
of  a  current  is  called  its  set ;  a  current 
which  flows  towards  the  nnw.  quarter, 
is  said  to  set  nnw.  The  velocity  of  a 
current  is  called  its  drift. 

SETA.  Literally,  a  bristle ;  hence 
applied  to  the  bristle-like  stalk  which 
supports  the  theca  of  mosses ;  and, 
hence,  the  epithet  setose  denotes  a  sur- 
face covered  with  short,  stiff  hairs,  as  the 
leaf  of  bugloss,  the  pappus  of  some  com- 
posite plants,  &c. 

SEVENTH.  In  Music,  a  dissonant 
interval,  of  which  there  are  three  kinds, 
the  minor  or  ordinary  seventh,  from  G 
to  F;  the  diminished  seventh,  from  C 
sharp  to  B  flat ;  and  the  major  or  sharp 
seventh,  fro  n  C  to  B. 

SE'VERITE.  A  hydrated  silicate  of 
alumina,  found  near  St.  Sever  in  France, 
in  a  gravelly  soil,  in  pieces  from  two  to 
five  inches  in  diameter. 

SEXTANS.  The  Sextant;  a  modern 
southern  constellation,  consisting  of 
forty-one  stars,  situated  between  Re- 
gulus  and  Cor  Hydrae. 

SEXTANT.  An  astronomical  and 
nautical  instrument,  commonly  called 
Hartley's,  by  means  of  which  the  direct 
angular  distance  of  any  two  objects  may 
be  measured,  or  the  altitude  of  a  single 
one  determined,  either  by  measuring  its 
distance  from  the  visible  horizon  (such 
as  the  sea-offing,  allowing  for  its  dip),  or 
from  its  own  reflection  on  the  surface  of 
mercury.  The  principle  of  this  instru- 
ment is  the  optical  property  of  reflected 
rays,  thus  announced: — "The  angle  be- 
tween the  first  and  the  last  directions  of  a 
ray  which  has  suffered  two  reflections  in 
one  plane,  is  equal  to  twice  the  inclina- 
tion of  the  reflecting  surfaces  to  each 
other." 

SEXTILE  ASPECT.  An  astrological 
term,  denoting  the  aspect  of  two  planets, 
when  they  are  distant  from  each  other 
the  sixth  part  of  a  circle,  or  sixty  de- 
grees. 

SEXUAL  SYSTEM.  A  mode  of  ar- 
ranging plants,  invented  by  Linnaeus, 
and  founded  upon  the  number  and  pecu- 
liarities of  the  sexual  organs.  See 
Botany. 

SHADOW.  If  an  opaque  body  be 
enlightened  on  one  side  only,  the  side 
which  is  more  remote  from  the  source  of 
light  will  continue  dark,  and  beyond  it 
there  will  be  a  space  not  affected  by  the 
light ;  this  constitutes  the  shadoio  of  the 
302 

I 


opaque  body.  If  any  object  intercept 
this  space,  that  side  of  it  which  is  next 
to  the  opaque  body  will  be  darkened  by 
the  projection  of  the  shadow  upon  it. 

SHALE  {schalen,  German,  to  peel,  to 
split).  A  provincial  term  adopted  by 
geologists  to  denote  an  indurated  slaty 
clay,  or  argillaceous  matter,  indurated, 
with  a  slaty  structure,  and  a  dull  grey 
streak,  and  naturally  divided  into  laminae 
parallel  to  the  plane  of  deposition.  When 
much  intermixed  with  carbonaceous  mat- 
ter, and  impregnated  with  bitumen,  it 
is  usually  named  bituminous  shale. 
When  highly  impregnated  with  silica, 
it  passes  into  flinty  slate. 

SHARP.  A  character  in  Music, 
marked  ft,  employed  to  raise  any  note 
of  the  natural  scale,  a  semitone  higher. 
The  double  sharp,  marked  x ,  is  used  in 
chromatic  music  for  raising  a  note  two 
semitones  above  its  natural  state.  Thus 
C  double  sharp  is  D  natural. 

SHEAR-STEEL.  This  substance,  so 
called  because  fitted  for  making  clothiers' 
shears,  scythes,  &c,  is  prepared  by  lay- 
ing several  bars  of  common  steel  toge- 
ther, and  heating  them  in  a  furnace  until 
they  acquire  the  welding  temperature. 
The  bars  are  then  beaten  together  with 
forge-hammers,  after  which  they  are 
drawn  anew  into  bars  for  sale. 

SHELL  LIMESTONE.  Muschelkalk. 
A  compact  limestone,  of  a  smoke-grey 
colour,  and  in  certain  localities  contain- 
ing a  great  variety  of  fossils.  The  most 
esteemed  variety  for  ornamental  pur- 
poses is  that  from  Carinthia,  called 
lumachella,  or  fire  marble.  Shell  lime- 
stone is  distinguished  from  Magnesian 
limestone  by  its  never  presenting  the 
shells  of  the  genus  Producta,  which 
occur  in  this  deposit ;  and  from  the  Lias, 
by  the  absence  of  the  Ammonites  and 
Gryphaeae  which  characterize  the  latter. 

SHELL  MARL.  A  deposit  of  clay, 
peat,  and  other  substances  mixed  with 
shells,  which  collects  at  the  bottom  of 
lakes. 

SHIELDS  OF  LICHENS.  Little 
coloured  cups  or  lines,  also  called  scu- 
tella  and  apothecia,  appearing  on  the 
upper  surface  of  lichens;  they  are  sur- 
rounded by  a  rim,  and  contain  the  asci, 
or  sporuliferous  tubes. 

SHINGLE.  The  loose  and  completely 
water-worn  gravel  on  the  sea-shore. 

SIDEREAL  DAY  (sidus,  a  star).  The 
space  of  time  elapsing  between  two  con- 
secutive returns  of  a  star  to  the  same 
meridian.     This  is  equal  to  the  time 


SIL 


SIL 


occupied  by  one  entire  revolution  of  the 
earth  upon  its  axis.     See  Hour. 

SIDEREAL  YEAR  (sidus,  a  star). 
The  period  of  time  in  which  the  earth 
makes  one  complete  revolution  in  its 
orbit ;  that  is,  from  any  given  star  to  the 
same  again.     See  Hour. 

SIDERUM.  The  name  given  by  Berg- 
mann  to  phosphuret  of  iron. 

SI'ENITE  or  SY'ENITE.  A  compound 
granular  aggregated  rock,  composed  of 
felspar  and  hornblende,  and  sometimes 
quartz  and  black  mica.  It  is  found  at 
Syene  in  Egypt,  and  other  places. 

SIGHT,  FIELD  OF.  The  field  of  a 
telescope  may  be  measured  by  directing 
the  instrument  to  some  star  in  or  very 
near  to  the  equator,  care  being  taken 
that  it  shall  pass  over  the  middle  of  the 
field,  and  then  count  the  number  of 
seconds  which  elapse  during  its  passage  : 
four  seconds  of  time  will  make  an 
angle  of  one  minute  for  the  field  of 
vision. 

SIGNS  of  the  ZODIAC.  The  ecliptic 
is  usually  divided  by  astronomers  and 
by  globe-makers  into  1 2  signs  of  30  de- 
grees each,  answering  to  twelve  constel- 
lations, with  the  following  names  and 
signs ;  the  parts  adjacent  to  the  ecliptic 
being  called  the  zodiac: — 

Aries  T  from     0°   to    30° 

Taurus   8    —      30°  —    60° 

Gemini  II    —      60°  —    90° 

Cancer    25    —      90°  —  120° 

Leo &    —    120°  —  150° 

Virgo  1tt>    —     150°  —  180° 

Libra  :£=—    180°  —  210° 

Scorpio   rq    —    210°  —  240° 

Sagittarius    ...  $    —    240°  —  270° 
Capricornus  ...  Vf    —    270°  —  300° 

Aquarius    S»    —    300°  —  330° 

Pisces K    —    330°— 360° 

Of  these  signs,  the  first  six  are  called 
northern,  lying  on  the  north  side  of  the 
equator ;  and  the  last  six  are  called 
southern,  being  situated  to  the  south  of 
the  equator. 

SILENA'CEiE.  A  sub-order  of  the 
family  of  plants  termed  Caryophyllaceae, 
distinguished  from  the  other  sub-order, 
or  Alsinacece,  by  the  possession  of  a 
tubular  calyx  and  clawed  petals. 

SILEX.  The  Latin  term  for  flint ; 
the  name  of  one  of  the  pure  earths,  of 
which  flint  is  wholly  composed ;  in 
chemical  language,  it  is  an  oxide  of 
silicon,  forming  the  basis  of  chalce- 
dony, cornelian,  jasper,  &c.  French 
geologists  have  applied  the  term  as  a 
generic  name  for  all  minerals  composed 
303 


entirely  of   silex,   of   which  there    are 
many  different  external  forms. 

1.  Silica.  Siliceous  earth;  the  oxide 
of  silicon,  constituting  almost  the  whole 
of  silex,  or  flint.  It  combines  with  many 
of  the  metallic  oxides,  and  is  hence 
sometimes  called  silicic  acid. 

2.  Silicate.  A  chemical  compound  of 
silica  and  another  substance,  as  silicate 
of  iron. 

3.  Siliceous.  Of  or  belonging  to  the 
earth  of  flint.  A  siliceous  rock  is  one 
composed  mainly  of  silex. 

4.  Silicified.  Any  substance  which  is 
petrified  or  mineralized  by  siliceous 
earth. 

5.  Silicon  or  Silicium.  An  elementary 
body  very  abundant  in  the  mineral  king- 
dom, constituting  the  basis  of  silica.  It 
is  a  dark-brown,  inflammable  substance, 
without  metallic  lustre. 

SILI'CULA.  A  diminutive  of  siliqua, 
and  applied,  in  botany,  to  a  fruit  of  the 
same  construction,  but  shorter  and 
broader  than  the  siliqua,  as  in  candy- 
tuft. 

SILIQUA.  A  fruit  consisting  of  two 
carpels  cohering  together,  the  placentae 
of  which  are  parietal,  and  separate  from 
the  valves,  presenting  a  kind  of  frame 
called  areplum,  and  connected  by  a  mem- 
branous expansion,  as  in  the  stock. 

SI'LLIMANITE.  A  crystallized  va- 
riety of  silicate  of  alumina,  found  at 
Saybrook  in  Connecticut,  in  a  vein  of 
quartz  penetrating  gneiss. 

SILT.  The  more  comminuted  sand, 
clay,  and  earth,  which  are  transported  by 
running  water.  It  is  often  accumulated 
by  currents  in  banks.  Thus,  the  mouth 
of  a  river  is  silted  up  when  its  entrance 
into  the  sea  is  impeded  by  such  accumu- 
lations of  loose  materials. 

SILU'RIAN  SYSTEM.  The  name 
given  by  Mr.  Murchison  to  the  upper 
part  of  the  lower  series  of  secondary 
rocks,  from  its  being  highly  developed 
in  that  part  of  Wales  which  was  formerly 
inhabited  by  the  Silures,  viz.,  the  coun- 
ties of  Hereford,  Radnor,  Brecon,  Caer- 
marthen,  and  Pembroke.  He  divides  it 
into  two  portions — the  Lower,  comprising 
the  Llandeilo  Flags  and  the  Caradoc 
Limestone ;  and  the  Upper,  consisting 
of  the  Wenlock  Limestone  and  the  Lud- 
low Rocks. 

SILURIDiE.  A  family  of  malacoptery- 
gious,  or  soft-spined  fishes,  distinguished 
from  all  other  families  of  the  order  by 
the  absence  of  true  scales,  having  only  a 
naked  skin,  or  large  bony  plates. 


SI  N 


S  I  P 


SILVAN.  The  name  given  by  Werner 
to  the  metal  tellurium. 

SILVER.  Argentum.  A  white  metal 
occurring  often  in  the  metallic  state  in 
mines,  and  in  combination  with  ores  of 
lead,  from  which  it  is  separated  by  cupel- 
lation.  Horn  silver  is  the  chloride,  re- 
sembling horn  in  consistence.  Fulmi- 
nating silver  is  an  explosive  substance, 
formed  of  oxide  of  silver  and  ammonia. 

SILVER  GLANCE.  Vitreous  silver,  or 
sulphuret  of  silver;  a  mineral  occurring 
massive,  crystallized,  and  in  other  ex- 
ternal forms,  among  which  are  the  lami- 
nar and  the  capillary.  The  black  silver 
ore  appears  to  be  a  pulverulent  variety 
of  this  species. 

SIMARUBACEiE.  The  Quassia  tribe 
of  Dicotyledonous  plants.  Trees  or 
shrubs  with  leaves  alternate ;  flowers 
polypetalous ;  stamens  twice  as  many  as 
the  petals,  hypogynous  ;  ovarium  4-  or  5- 
celled ;  fruit,  indehiscent  drupes. 

SI'MIADiE  (simia,  an  ape).  A  family 
of  Quadrumanous  animals,  including 
the  apes,  monkeys,  and  baboons  of  the 
Old  World. 

SIMILAR  FIGURES.  In  Geometry, 
figures  are  termed  similar,  when  they 
resemble  one  another  in  shape,  without 
reference  to  their  size  ;  when  the  latter 
point  of  resemblance  exists,  the  figures 
are  said  to  be  equal. 

SI'MILOR.  The  designation  of  an 
alloy  of  zinc  and  copper. 

SIMOON.  An  Arabic*  term  denoting 
poison,  and  applied  to  a  hot  wind  which 
occurs  in  most  countries  situated  near 
sandy  deserts,  and  blows  from  the  quar- 
ter of  the  desert.  In  Turkey  the  wind 
is  called  Samieli ;  in  Egypt,  Khamsin ; 
in  Guinea  and  Senegambia,  Harmat- 
tan. 

SIMPLE  MINERAL.  A  term  applied 
to  individual  mineral  substances,  as  dis- 
tinguished from  rocks,  the  latter  being 
usually  an  aggregation  of  simple  mine- 
rals. They  are  not  simple  in  regard  to 
their  nature ;  for,  when  subjected  to  che- 
mical analysis,  they  are  found  to  consist 
of  a  variety  of  different  substances.  Py- 
rites is  a  simple  mineral  in  the  sense  in 
which  we  use  the  term,  but  it  is  a  chemi- 
cal compound  of  sulphur  and  iron. 

SINE  and  COSINE.  In  Trigono- 
metry, the  sine  of  any  arc  of  a  circle  is 
the  straight  line  drawn  from  one  ex- 
tremity of  the  arc  perpendicular  to  the 
radius  passing  through  the  other  extre- 
mity. The  cosine  is  the  sine  of  the  com- 
plement of  an  angle  or  arc,  the  prefix 
304 


co  being  merely  the  abbreviation  of  com- 
plement, first  introduced  by  Gunter. 

SINGULAR  TERM.  A  singular  term, 
in  Logic,  is  that  which  stands  for  one 
individual,  and  cannot,  therefore,  be 
predicated  affirmatively  of  any  thing  but 
that  individual.     See  Common  Term. 

A  Singular  Proposition  is  one  which 
has  for  its  subject  either  a  singular  term, 
or  a  common  term  limited  to  one  indi- 
vidual by  a  singular  sign,  e.  g.  "  This." 
Such  a  proposition  is  universal,  when  the 
whole  of  the  subject  is  spoken  of;  parti- 
cular, when  only  a  part  is  spoken  of,  e.  g. 
"  Non  omnis  moriar." 

SINTER  (sintern,  to  drop).  A  Ger- 
man name  for  a  rock  precipitated  from 
mineral  waters.  Calcareous  sinter  is  car- 
bonate of  lime  deposited  in  layers ;  sili- 
ceous sinter,  a  variety  of  common  opal. 

1.  Sinter,  ceraunian.  A  variety  of 
quartz  consisting  of  siliceous  tubes 
found  in  the  sands  of  the  Senner  Heath 
in  the  county  of  Lippe,  where,  on  ac- 
count of  their  supposed  origin,  they  are 
called  lightning  tubes,  and  hence  are 
derived  the  terms  fulgurite,  astraphya- 
lite,  &c. 

2.  Sinter,  quartz.  Stalagmitic  quartz, 
the  most  remarkable  varieties  of  which 
are  the  siliceous  concretions  deposited 
by  the  celebrated  hot  spring  in  Iceland, 
the  Geyser.  Another  variety  is  the  pearl- 
sinter  from  Santa-Fiora  in  Tuscany 
(whence  it  has  obtained  the  name  of 
fiorite),  and  from  the  island  of  Ischia. 

SINUATED  {sinus,  a  bay  or  cavity). 
Having  a  wavy  margin,  produced  by 
alternations  of  projecting  lobes  and  in- 
dentations. 

SIPHON  (<ri<pu)v,  a  tube).  A  hydraulic 
instrument  used  for  emptying  liquids 
from  one  vessel  into  another,  without 
disturbing  the  mass  of  the  liquid.  It  is 
merely  a  bent  tube  of  which  one  leg  is 
longer  than  the  other.  When  this  is 
filled  with  liquid,  and  the  shorter  leg 
is  immersed  in  a  vessel  to  be  emptied, 
the  atmospheric  pressure  on  the  surface 
of  the  liquid  will  cause  it  to  rise  in  the 
shorter  leg,  and  thus  a  continuous  stream 
will  be  produced. 

SIPHON  (in  Zoology).  A  sucker ;  a 
fleshy  process,  generally  long,  cylindrical, 
and  hollow,  protruded  by  the  carnivorous 
and  testaceous  animals  from  the  base  or 
channel  of  their  shells.  The  same  term 
is  applied  to  the  slender  shelly  tube 
which  connects  the  chambers  of  cepha- 
lopod  shells,  or  the  nautili. 

SIPHONO'STOMOUS  (<n>«v,  a  tube, 


SLA 


SMI 


trrona,  a  mouth).  A  designation  of  ani- 
mals with  a  suctorious  mouth  like  a 
tube.  The  term  is  usually  applied  to  an 
order  of  the  edentulous  Crustacea  which 
are  so  characterized,  as  the  caligus. 
Under  the  term  Siphonobranchiata,  De 
Blainville  describes  the  first  order  of  his 
first  sub-class  of  Mollusca,  Paracephalo- 
phora  dioica. 

SIPHU'NCLE.  A  long  tube,  partly 
calcareous  and  membranous,  which  passes 
through  all  the  compartments  of  the  shells 
of  certain  cephalopods ;  the  membranous 
siphuncle  is  continued  into  the  animal, 
and  terminates  in  a  cavity  contained 
within  its  body. 

SIRE'NE.  An  instrument,  invented 
by  Caignard  Latour,  for  determining  the 
number  of  musical  vibrations.  The  notes 
are  produced  in  it  by  breaks  in  a  con- 
stant stream  of  air,  these  breaks  occur- 
ring at  equal  intervals  of  time,  so  that 
after  each  break  there  is  a  new  wave  of 
air.  When  the  number  of  waves  amounts 
to  32  in  a  second,  the  lowest  note  is 
emitted,  and  the  number  may  be  in- 
creased to  about  16,000  per  second,  when 
the  note  degenerates  into  a  mere  whistle. 

SIR'IUS.  The  Dog-star;  a  star  of  the 
first  magnitude  in  the  southern  constel- 
lation Canis  major. 

SIRO'CCO.  The  name  given  to  the 
hot  wind  which  occasionally  blows  in 
Sicily,  and  which  is  supposed  to  derive 
its  origin  from  the  excessively  heated 
deserts  of  Africa.     See  Solano. 

SPTTINjE  {sittia,  the  nuthatch).  Sit- 
tine  birds,  or  Nuthatches  ;  a  family  of  the 
Reptatrices  of  Macgillivray.  In  the  form 
of  the  feet  and  claws  these  birds  resemble 
the  Certhiadae,  while  in  the  structure  of 
the  bill  they  somewhat  resemble  Wood- 
peckers, and  in  their  general  aspect  and 
habits  approach  the  Parinae.  By  other 
writers,  the  Nuthatches  are  included  in 
the  family  Certhiadae,  belonging  to  the 
Insessores  or  Perchers. 

SKO'RODITE  (vKdpodov,  garlic).  Cu- 
preous arseniate  of  iron ;  a  mineral  sub- 
stance which  appears  to  be  closely  allied 
to  Bournon's  martial  arseniate  of  copper. 
The  name  is  derived  from  the  garlicky 
odour  it  emits  when  heated. 

SKY.  The  popular  name  for  the  blue 
expanse  of  atmospheric  air.  The  blue 
colour  of  the  sky  has  been  found  by 
Brewster  to  be  due  to  light  which  has 
suffered  polarization,  and  which  is,  there- 
fore, reflected  light,  like  the  white  light 
of  clouds. 

SLAG.  The  glassy  compounds  pro- 
305 


duced  during  the  reduction  of  metallic 
ores  by  means  of  fluxes. 

SLATE.  Clay  slate.  A  geological  term 
for  the  well-known  stone  with  which 
houses  are  roofed,  and  which  consists 
mainly  of  clay.  It  agrees  with  mica- 
slate  in  its  fissile  structure,  but  differs  in 
having  its  cleavage  more  or  less  trans- 
verse to  the  line  of  its  stratification. 

SLATE-CLAY.  Another  name  for 
shale,  or  argillaceous  matter,  indurated, 
with  a  slaty  structure,  and  a  dull  grey 
streak. 

SLATE-SPAR.  Schiefer  Spar.  The 
name  of  a  sub-species  of  limestone. 

SLATE,  STONESFIELD.  A  com- 
ponent part  of  the  Lower  Oolitic  Series, 
consisting  of  slaty  calcareous  lime- 
stone. 

SLATY  GNEISS.  A  variety  of  gneiss, 
of  which  the  texture  is  usually  minute, 
and  the  scales  of  mica  or  crystals  of 
hornblende  form  small  laminae,  render- 
ing the  rock  easily  fissile. 

SLEET.  Half-melted  snow,  consti- 
tuting an  intermediate  condition  between 
that  of  snow  and  that  of  rain. 

SLPCKENSIDE.  The  name  given 
by  the  Derbyshire  miners  to  the  compact 
and  specular  variety  of  galena,  or  sul- 
phuret  of  lead,  from  the  smoothness  of 
its  surface.  It  occurs  lining  the  walls  of 
very  narrow  rents. 

SLIDING  RULE.  An  instrument 
consisting  of  two  parts,  one  of  which 
slides  along  the  other,  for  the  mechanical 
performance  of  addition  and  subtraction, 
and  also  of  multiplication  and  division, 
by  the  use  of  logarithmic  scales,  instead 
of  scales  of  equal  parts. 

SMALT  (schalmz,  Germ.).  A  blue- 
coloured  glass,  obtained  by  heating  zaffre, 
or  the  impure  oxide  of  cobalt,  with  sand 
and  potash,  reduced  to  powder.  It  is  the 
blue-stone  used  in  washing. 

SMARA'GD  (arfjidpafdoi).  Anciently, 
this  term  was  applied  to  a  semi-trans- 
parent stone  like  the  aqua  marina,  but  is 
now  usually  employed  to  designate  the 
emerald. 

SMELTING.  The  reduction  of  me- 
tallic ores,  for" the  purpose  of  extricating 
the  pure  metal.  With  the  ore  and  fuel  a 
third  substance,  called  a  flux,  is  usually 
added,  the  object  of  which  is  to  form  a 
fusible  compound  with  the  earthy  matter 
of  the  ore. 

SMILA'CEjE.  The  Smilax  tribe  of 
Monocotyledonous  plants.  Herbaceous 
climbing  plants ;  flowers  hexapetalo'ide- 
ous,  hermaphrodite,    sometimes    diced- 


SOD 


SOL 


ous  ;  stamens  6 ;  ovarium  3-celled ;  fruit 
a  berry. 

SMOKE.  Smoke  consists  of  the  un- 
consumed  gaseous  elements  of  any  body, 
and,  consequently,  arises  from  imperfect 
combustion. 

SNOW.  The  frozen  visible  vapour 
composing  clouds.  A  flake  of  snow  ex- 
hibits a  beautiful  display  of  minute  crys- 
tals, often  possessing  the  greatest  variety 
of  forms.  The  production  of  snow  offers 
the  most  simple  case  of  the  precipitation 
of  water  from  the  atmosphere. 

SNOW  LINE.  That  limit  of  elevation 
in  every  latitude  at  which  the  air  attains 
the  temperature  of  freezing  water.  The 
line  of  perpetual  congelation  is,  of  course, 
the  summer  limit. 

SNOW,  RED.  The  colouring  matter 
of  this  substance  appears  to  be  an  alga- 
ceous  plant,  named  protococcus  nivalis. 
Agardh's  definition  of  Protococcus  is 
merely,  "  plants  with  aggregated,  not 
mucous  globules."  To  this  Greville 
added,  "  globules  containing  granules 
seated  on  a  transparent  gelatinous 
mass." 

SNOWDON  ROCKS.  One  of  the 
subordinate  divisions  of  the  Cambrian 
Group  of  Rocks,  of  many  colours  and 
textures,  varying  from  fragmentary  to 
the  finest  roofing-slate. 

SOAP.  A  compound,  in  definite  pro- 
portions, of  certain  principles  in  oils, 
fats,  or  resin,  with  a  salifiable  base. 
Hard  soap  is  made  of  soda  and  fatty  or 
resinous  matters ;  soft  soap  is  made  of 
caustic  potash  and  acid  oil  or  fat. 

SOAPSTONE.  Steatite.  A  mineral 
consisting  of  silicate  of  alumina  and 
magnesia,  and  named  from  its  resem- 
blance to  mottled  soap  and  from  its  unc- 
tuous feel. 

SO'BOLES.  The  botanical  term  for 
the  creeping  stem,  or  slender  stem  of  cer- 
tain plants,  which  creeps  horizontally 
below  the  surface  of  the  earth,  emitting 
roots  and  new  plants  at  intervals,  as  in 
triticum  repens. 

SODA.  The  protoxide  of  sodium ;  an 
alkali  procured  from  the  ashes  of  marine 
plants ;  formerly  called  the  mineral 
alkali,  from  its  being  found  native, 
under  the  name  of  natron,  in  mineral 
seams  or  crusts. 

'  SODA-WATER.  A  solution  of  the 
bicarbonate  of  soda  in  water,  when  an 
additional  quantity  of  carbonic  acid  has 
been  forcibly  combined  with  it. 

SO'DALITE.     A   mineral    substance 
consisting  of  a  silicate  of  soda  and  alu- 
306 


mina,  found  in  Greenland,  in    Mount 
Vesuvius,  and  in  Siberia. 

SODIUM.  Natrium.  A  white  metal 
with  the  aspect  of  silver,  soft  and  mal- 
leable at  32°,  quite  liquid  at  194°,  and 
volatilized  at  a  red  heat.  Davy  obtained 
this  metal  by  the  voltaic  decomposition 
of  soda,  immediately  after  the  discovery 
of  potassium. 

SOIL,  VEGETABLE.  The  external 
thin  layer  of  earth  in  which  plants  grow, 
composed  of  fragments  of  minerals,  vege- 
tables, and  animals,  reduced  to  a  great 
degree  of  tenuity. 

SOL.  The  Sun;  a  globe,  1,300,000 
times  greater  than  the  earth,  and  situated 
at  a  mean  distance  of  94^  millions  of 
miles  from  the  earth. 

SOLANA'CE^E.  The  Nightshade  tribe 
of  dicotyledonous  plants.  Herbaceous 
plants  or  shrubs,  with  leaves  alternate ; 
flowers  monopetalous,  regular;  stamens 
inserted  into  the  corolla;  ovarium  2- 
celled ;  fruit  succulent. 

SOLA'NO.  The  name  given  to  a  hot 
wind  which  blows  in  Spain  and  Portugal. 
It  is  a  modified  sirocco. 

SOLAR  DAY.  The  interval  between 
two  transits  of  the  sun  over  the  meri- 
dian. It  is  longer  than  the  sidereal  day ; 
for  if  the  sun  move  slowly  eastward,  and 
if  it  be  on  the  meridian  with  a  certain 
star  to-day,  then  to-morrow,  when  that 
star  comes  on  the  meridian,  the  sun 
will  be  a  little  to  the  eastward,  or  not 
yet  on  the  meridian :  that  is,  the  solar 
day  is  not  quite  completed  in  a  sidereal 
day. 

SOLAR  PHOSPHORUS.  A  general 
term  for  those  substances  which,  after 
exposure  to  light,  exhibit  phosphorescent 
properties,  as  Canton's  phosphorus,  &c. 

SOLAR  SYSTEM.  The  Solar  System 
comprises  the  sun  as  a  centre,  and  thirty 
other  bodies,  which  revolve  round  him 
in  regular  periods  and  at  various  dis- 
tances.    See  Planet. 

SOLDER.  A  simple  or  mixed  metal, 
by  means  of  which  metallic  bodies  can 
be  firmly  united  with  each  other.  Hard 
solders  are  ductile,  malleable,  and  are 
usually  prepared  of  the  same  metal  with 
that  which  is  to  be  soldered,  with  the 
addition  of  some  other ;  soft  solders  melt 
readily,  are  partly  brittle,  and  therefore 
not  malleable ;  bismuth  is  much  used  in 
the  composition  of  soft  solders,  from  its 
capability  of  forming  with  several  metals 
compounds  of  remarkable  fusibility. 

SOLDERING.  The  process  of  uniting 
the  surfaces  of  metals,  by  the  interven- 


SOL 


SOL 


tion  of  a  more  fusible  metal,  which, 
being  melted  upon  each  surface,  serves, 
partly  by  chemical  attraction,  and  partly 
by  cohesive  force,  to  bind  them  together. 
See  Solder. 

Soldering,  autogenous.  This  process 
consists  in  the  union  of  two  pieces  of 
metal  without  the  interposition  of  any 
solder,  by  fusing  them  at  the  point  of 
junction  by  jets  of  flame  from  a  gas 
blow -pipe. 

SOLENPNjE.  The  Solens;  a  sub- 
family of  the  Myadae,  or  Gaping  bi- 
valves, named  from  the  genus  solen,  and 
having  their  shells  always  open  at  both 
extremities. 

SO'LENOID  (a-a>\r]v,  a  channel,  a  cy- 
lindrical box,  ei3or,  likeness).  The  name 
given  by  Ampere  to  what  is  otherwise 
called  an  electro-dynamical  screw,  or  elec- 
tro-dynamical cylinder.  It  consists  of  a 
linear  series  of  circular  currents  passing 
at  right  angles  to  the  axis  of  the  spiral 
conductor. 

SOLFATA'RA.  A  volcanic  vent  from 
which  sulphur,  sulphureous,  watery,  and 
acid  vapours  and  gases  are  emitted.  The 
name  is  derived  from  Solfaterra,  the  cele- 
brated mountain  of  Naples,  called  by  the 
ancients  Phlegrtei  campi. 

SOLID.  In  geometry,  a  solid  figure  is 
one  enclosed  by,  at  least,  four  planes  or 
faces,  and  named  from  the  number  of  its 
faces ;  thus  a  figure  with  four  faces  is 
called  a  tetrahedron  ;  one  with  six,  a 
hexahedron;  those  with  more  than  six, 
polyhedrons.  Solids  are  also  named  ac- 
cording to  the  figures  and  positions  of 
their  faces,  as  the  prism,  the  parallelo- 
piped,  &c. 

1.  Solid  dimension.  Length  is  said  to 
be  a  quantity  of  one  dimension,  surface 
of  two,  and  solidity  of  three,  viz.  length, 
breadth,  and  thickness.  The  right  line, 
the  right  surface  or  rectangle,  and  the 
right  solid  or  rectangular  parallelopiped 
are  the  implements  of  mensuration. 

2.  Solid  of  least  resistance.  A  term 
applied  to  a  geometrical  solid  of  such  a 
shape  as  will  enable  it  to  move  with  the 
least  resistance  through  the  air,  water, 
or  other  fluid.     Such  a  solid  is  a  conoid. 

3.  Solids',  regular.  A  regular  solid  is 
one  whose  faces  are  equal,  equilateral, 
and  equiangular  plane  figures.  There 
are,  but  cannot  be  more  than,  five  regu- 
lar solids  ;  three  of  these  have  triangular 
faces,  one  square  faces,  and  the  remain- 
ing one  pentagonal  faces. 

4.  Solid  problem.  A  solid,  as  distin- 
guished from  a  plane,  problem,  in  geo- 

307 


metry,  is  one  which  cannot  be  con- 
structed by  the  intersections  of  circles 
and  straight  lines,  but  requires  for  its 
construction  the  description  of  one  or 
more  conic  sections. 

SOLID  (in  Physics).  A  term  denoting 
that  constitution  of  matter  in  which  the 
attractive  forces  of  the  molecules  are 
greater  than  the  repulsive,  and  the 
molecules  consequently  cohere  with  more 
or  less  force.  In  the  liquid  state,  the 
two  forces  are  balanced ;  in  the  gaseous 
the  repulsive  predominates. 

SOLIDIFICATION.  The  condition 
exactly  opposed  to  liquefaction;  it  is 
the  state  assumed  by  liquid  bodies  on 
parting  with  their  free  caloric.  With- 
out adhering  strictly  to  this  rule,  we 
generally  use  the  term  solidification,  when 
we  speak  of  such  fluids  as  become  solid 
at  a  temperature  higher  than  that  of 
freezing  water;  and  freezing,  when  we 
speak  of  such  as  become  solid  at  a  point 
below  32°. 

SOLIDU'NGULA  (sola  ungula,  a  sin- 
gle hoof).  Solipeds.  A  group  of  pachy- 
dermatous animals,  comprising  quadru- 
peds with  only  one  apparent  toe,  and  a 
single  hoof  to  each  foot,  as  the  horse. 

SOLITA'RIUS.  The  Hermit ;  an  ob- 
scure cons  ellation  of  Lemonnier,  situ- 
ated a  little  above  Centaurus,  near  the 
tail  of  Hydra. 

SO'LSTICES  {sol,  the  sun,  sto,  to 
stand).  The  two  extreme  points  of  the 
Sun's  apparent  course  north  and  south 
of  the  equator.  These  are  the  first  points 
of  Cancer  and  of  Capricorn,  where  the 
sun  appears  to  make  a  stand,  going  nei- 
ther northward  nor  southward.  The  two 
corresponding  periods  of  the  year  are 
called  the  Summer  and  the  Winter  sol- 
stices, from  the  seasons  in  which  the 
apparent  standings  of  the  sun  occur. 

SOLUBI'LITY.  A  contrivance  of 
nature  for  facilitating  the  dispersion  of 
seeds  in  some  plants.  It  arises  from  the 
presence  of  certain  transverse  contrac- 
tions of  a  1-celled  pericarp,  through 
which  it  finally  separates  into  several 
closed  portions,  as  in  ornithopus,  entada, 
&c. 

SOLUTION  {solvo,  to  dissolve).  The 
operation  of  dissolving  a  solid  or  aeri- 
form body  in  a  liquid.  The  condition  of 
the  solid  or  aeriform  body  is  called  its 
solution ;  the  liquid  which  effects  the 
change  is  the  solvent.  When  the  liquid 
will  dissolve  no  more  of  the  solid,  but 
allows  the  excess  to  be  deposited  on  the 
bottom  of  the  vessel,  it  is  said  to  be  satti- 


SON 


SOR 


rated,  and  the  mixed  fluid  is  then  a 
saturated  solution  of  the  substance  which 
it  contains. 

1.  Chemical  solution.  This  term  de- 
notes that  a  perfect  chemical  union  of 
the  solid  with  the  liquid  is  produced,  in 
accordance  with  the  laws  of  definite  pro- 
portions. Both  the  constituents  of  the 
compound  exhibit  a  change  in  their  pro- 
perties, and  are  combined  in  an  entirely 
new  substance  formed  by  their  union, 
which  substance,  on  the  completion  of 
the  process,  generally  assumes  a  solid 
form,  that  is,  it  becomes  crystallized. 

2.  Mechanical  solution.  This  is  the 
mere  union  of  a  solid  with  a  liquid,  in 
such  a  manner  that  its  aggregate  form  is 
changed  without  any  alteration  being 
effected  in  the  chemical  properties  of 
either  the  solid  or  its  solvent.  If  the 
latter  be  separated  from  the  solution,  as 
by  heat,  the  former  which  has  been  dis- 
solved is  obtained  again  with  its  chemi- 
cal properties  unaltered. 

3.  Moist  and  dry  solutions.  In  the 
former,  at  least  one  of  the  bodies,  the 
solvent,  must  be  a  liquid  ;  in  the  latter, 
both  of  the  substances  are  solids,  and 
liquefaction  must  be  brought  about  by 
means  of  heat  before  any  combination 
will  take  place.  Bronze,  for  instance,  is 
such  a  solution  of  copper  and  tin. 

SO'LVENT  (solvo,  to  dissolve).  A 
fluid  which  causes  the  solution  of  a  solid 
or  aeriform  body ;  chemically,  a  men- 
struum. Some  of  the  most  powerful 
solvents  are  the  sulphuric,  nitric,  and 
chloric  acids. 

SOMMERVILLITE.  A  new  mineral 
from  Vesuvius,  occurring  in  cavities  with 
crystallized  black  mica. 

SO'MMITE.  Nepheline.  Rhomboidal 
felspar,  occurring,  in  drusy  cavities,  at 
Monte  Somma,  near  Naples,  in  granular 
limestone. 

SONI'FEROUS  BODIES.  For  the 
production  of  sound  there  is  required, 
besides  the  sonorous  body,  one  that  is 
adapted  to  convey  the  sound,  or  rather 
the  vibrations,  of  the  former  body  to  the 
ear :  bodies  of  this  class  are  called  soni- 
ferous bodies,  and  they  are  such  as  can 
transmit  the  vibrations,  imparted  to 
them  by  the  sonorous  bodies,  in  all 
directions  throughout  their  mass,  and 
with  equal  velocity. 

SONO'METER.  An  apparatus  for 
illustrating  the  phenomena  presented  by 
sonorous  bodies,  and  the  ratios  of  their 
vibrations,  by  the  transverse  vibrations 
of  tense  cords.  See  Monochord. 
308 


SONOROUS  FIGURES.  This  sub- 
ject has  been  already  noticed  under  the 
term  Nodal  Lines.  To  make  these  figures 
visible,  and  to  render  them  permanent, 
strew  some  fine  sand  on  a  disc  of  glass 
or  metal ;  hold  the  disc  firmly  between 
two  fingers,  and  draw  a  violin-bow  down 
on  its  edge,  and  a  musical  note  will  be 
heard ;  at  the  same  instant  the  sand  will 
be  in  motion  and  gather  itself  to  those 
parts  which  continue  at  rest,  i.  e.  to  the 
nodal  lines.  The  figures  may  also  be 
seen  if  a  small  quantity  of  water  be 
poured  on  the  plate,  nay,  even  by  the 
rays  of  light  falling  on  it. 

SO'PHISM  {aocpiana,  a  captious 
argument,  a  fallacy).  An  argument 
which  appears  true,  but  is  fallacious. 
Sophisms  are  generally  traceable  to  the 
assumption  of  doubtful  premises,  or  the 
assumption  of  a  hypothetical  cause. 

SORBIC  ACID.  An  acid  obtained 
from  the  berries  of  the  Sorbus  aucuparia, 
or  Mountain  Ash.  It  appears  that  the 
sorbic  and  pure  malic  acids  are  identical. 
Sorbates  are  compounds  of  sorbic  or 
malic  acid  with  the  salifiable  bases. 

SORE'DIA  (dim.  of  o-o>p6r,  a  heap). 
Globuli  ;  glomeruli.  Small  heaps  of 
powdery  bodies  lying  upon  any  part  of 
the  surface  of  the  thallus  of  lichens. 
The  bodies  of  which  the  soredia  are 
composed,  are  called  conidia  by  Link, 
and  propagula  by  others. 

SORI'CID^.  The  Shrew  tribe;  a 
family  of  the  insectivorous  vertebrata, 
consisting  of  a  kind  of  carnivorous  mice, 
which,  though  they  do  not  burrow,  like 
the  talpidae,  retire  into  holes  during  the 
winter  for  repose,  and  are  partially 
aquatic  in  their  habits. 

SORFTES  ((rtopetTnf,  heaped  up,  from 
c-wpo?,  a  heap).  In  logic,  a  heap  of  syllo- 
gisms, the  conclusion  of  each  forming  the 
premiss  of  the  next  in  order.  In  the 
abridged ,  form  in  which  this  argument 
occurs,  the  predicate  of  the  first  pro- 
position is  made  the  subject  of  the 
next;  and  so  on,  to  any  length,  till, 
finally,  the  predicate  of  the  last  of  the 
premises  is  predicated  (in  the  conclusion) 
of  the  subject  of  the  first :  e.  g.  A  is  B, 
B  is  C,  C  is  D,  D  is  E ;  therefore  A  is  E. 

SORO'SIS  (o-upo?,  a  heap).  A  collec- 
tive fruit,  consisting  of  a  juicy  spike  or 
raceme,  having  all  its  ovaria  and  floral 
envelopes  cohering  into  a  single  mass,  as 
in  the  mulberry,  the  pine-apple,  the 
bread-fruit,  &c. 

SORUS  (<ro)p6?,  a  heap).  The  botani- 
cal term  for  each  cluster  of  sporuliferous 


sou 


SPE 


thecae  developed  on  the  under  surface  of 
the  fronds  of  Ferus. 

SO'THIAC  PERIOD.  A  term  em- 
ployed in  the  calendar  of  the  Egyptians 
and  the  Persians.  Their  year  is  supposed 
to  have  comprised  365  days,  so  that  every 
four  years  they  lost  a  day  in  the  solar  year, 
and,  after  a  period  of  1460  years,  called 
the  Sothiac  Period,  or  great  canicular 
year,  the  civil  and  the  solar  years  recom- 
menced at  the  same  time ;  or,  in  other 
words,  the  canicula  or  dog-star  would 
then  again  rise  heliacally  at  the  be- 
ginning of  their  year.  The  365  days  of 
the  year  composed  twelve  months,  each 
of  thirty  days,  and  the  five  remaining 
days  were  added  under  the  name  of 
epagomencc,  or  supplementary  days. 

SOUND.  A  sensation  produced  through 
the  ear,  by  the  vibrating  or  tremulous 
motion  of  a  sounding  body.  This  mo- 
tion is  communicated  to  the  surrounding 
air,  and  is  conveyed  by  this  medium  to 
the  drum  of  the  ear,  which  also  undergoes 
a  vibrating  motion,  and  this  last  motion, 
by  throwing  the  auditory  nerves  into 
action,  produces  the  sensation  of  hear- 
ing. 

1.  Sound,  waves  of.  Every  vibration  of 
a  sonorous  body  produces  a  progressive 
wave  in  the  air,  which  moves  in  a  di- 
rection perpendicular  to  the  surface  of 
such  body.  These  undulations  are  called 
waves  of  sound,  and  every  right  line,  per- 
pendicular to  their  surface,  or  to  that  of 
the  sonorous  body,  is  called  a  ray  of 
sound.  It  has  been  supposed  that  a 
wave  of  vibration,  "  the  sigh  of  a  drown- 
ing slave,"— proceeds  in  constant  undu- 
lation through  space,  and  a  similar  idea 
has  been  applied  to  the  radiations  of 
light  from  external  objects. 

2.  Sound,  Musical.  When  a  number 
of  sounds,  or  vibrations,  succeed  one 
another  with  such  regularity  as  to  pro- 
duce the  impression  of  a  single  sound, 
this  is  called  a  musical  sound.  The 
quantity  of  a  musical  sound  depends  on 
the  extent  and  velocity  of  the  vibrations, 
and  corresponds  to  the  strength  or  in- 
tensity of  the  sound.  The  quality  of  a 
sound  is  independent  of  its  quantity,  and 
relates  to  the  different  instruments  by 
which  it  is  emitted,  as  by  the  human 
voice,  the  cord  of  a  violin,  &c.  Our 
appreciation  of  the  quality  of  sounds  has 
not  been  satisfactorily  explained. 

SOUNDINGS.     This  term  denotes,  in 

hydrography, the  depths  of  water  in  rivers, 

harbours,  along  shore,  and  even  in  the 

open  seas.  The  term  is  also  applied  to  the 

309 


nature  of  the  ground  at  the  bottom  of  the 
water. 

SPA  WATER.  An  acidulous  chaly- 
beate, containing  more  iron  and  carbonic 
acid  than  any  other  mineral  spring. 

SPACE  {spatium).  A  general  term  for 
extension  in  all  directions.  From  the 
idea  of  space  follows  that  of  form,  which 
is  the  conception  of  the  manner  in  which 
one  part  of  space  is  separated  from  the 
rest ;  and  from  the  investigation  of  forms 
arises  geometry.  In  this  restricted  sig- 
nification, space  denotes  area,  as  when 
it  is  said  that  two  straight  lines  cannot 
enclose  a  space,  that  is,  an  area. 

SPADIX.  A  form  of  inflorescence,  in 
which  the  flowers  are  arranged  close  to- 
gether upon  a  succulent  axis,  which  is 
enveloped  in  a  sheath,  or  spathe.  This 
mode  of  inflorescence  is  characteristic  of 
the  natural  orders  Araceae  and  Acoraceae. 

SPANGLED  ROD.  A  glass  tube,  on 
the  surface  of  which  are  pasted  spangles 
of  tinfoil  in  a  spiral  form  and  at  small 
intervals.  An  electric  spark  transmitted 
along  such  a  conductor  appears  at  the 
same  instant  at  all  the  intervals. 

SPANISH  CHALK.  Steatite,  or 
soapstone;  a  sub-species  of  rhomboidal 
mica. 

SPAR  (spath,  German).  A  term  fre- 
quently applied  to  stones,  the  broken 
surfaces  of  which  present  polished  shi- 
ning plates,  placed  over  one  another  in 
horizontal  layers.  This  is  the  sparry 
texture,  and  minerals  of  this  kind  are 
generally  called  spathose. 

SPA'RID^.  Sparoides.  A  family  of 
acanthopterygious  fishes,  named  from 
the  genus  sparus,  or  Gilt-head.  The 
palate  is  edentulous,  but  the  jaws  are 
well  furnished  with  teeth,  and  it  is  upon 
the  various  modifications  of  the  teeth 
that  the  genera  are  formed. 

SPARRY  ANHYDRITE  Cube.  spar. 
A  sub-species  of  prismatic  gypsum,  found 
in  the  salt-mines  of  Halle,  &e. 

SPARRY  IRON.  Carbonate  of  iron, 
found  abundantly  in  limestone.  It 
affords  an  iron  well  suited  for  conver- 
sion into  steel. 

SPATHE'  {cnrddr),  any  broad  plate,  of 
wood  or  metal ;  a  flower-sheath).  The 
botanical  term  for  a  large  bract,  which 
envelopes  the  spadix  of  the  arum  and 
other  plants. 

SPECIES.  A  logical  species  is  a  pre- 
dicate which  is  considered  as  expressing 
the  whole  essence  of  the  individuals  of 
which  it  is  affirmed.  A  predicable  which 
expresses  only  a  part,  is  of  two  kinds  :  it 


SPE 


SP  IT 


may  express  the  material  part,  and  is 
then  called  the  genus ;  or  the  formal  and 
distinguishing  part,  and  is  then  called 
the  differentia.  Hence  the  genus  and 
differentia,  taken  together,  constitute  the 
species  ;  e.  g.  "  rational"  and  "  animal," 
constitute  "man." 

1.  Species  in  Natural  History.  Natu- 
ralists employ  the  term  "species"  in  a 
technical  sense,  or  "  second  intention," 
when  applied  to  organized  beings.  In 
this  case  it  denotes  such  individuals  as 
are  supposed  to  be  descended  from  a  com- 
mon stock,  or  which  might  have  so  de- 
scended ;  viz.  which  resemble  one  an- 
other (to  use  Cuvier's  expression)  as 
much  as  those  of  the  same  stock  do. 

2.  Species,  in  Mathematics.  Euclid 
employed  the  word  '  species'  in  its  pri- 
mitive sense  of  appearance :  when  the 
form  of  a  figure  is  given,  he  speaks  of 
the  figure  as  given  'in  species;'  thus, 
"  rectilineal  figures  are  said  to  be  given 
in  species,  which  have  each  of  their 
angles  given,  and  the  ratios  of  their  sides 
given.,r 

3.  The  term  species  was  employed  by 
Vieta  in  its  logical  sense,  as  opposed  to 
individual,  in  designating  the  algebraical 
notation  in  those  cases  in  which  letters 
were  used  for  numbers  in  a  general  sense. 
Thus  he  termed  the  logistics,  or  the  sci- 
ence of  calculation,  specious ;  and,  hence, 
the  language  of  algebra  was,  for  some 
time,  called  the  specious  notation. 

SPECIFIC.  A  term  denoting  any  pro- 
perty which  is  not  general,  but  confined 
to  an  individual  or  a  species. 

SPECTRUM.  This  Latin  term  de- 
notes an  ideal  form,  and  is  applied  to 
certain  optical  phaenomena,  described 
under  the  term  colours  accidental ;  and 
to  the  effect  of  refraction  on  a  ray  of 
light,  explained  under  the  word  pris- 
matic spectrum. 

SPECULAR  IRON  ORE.  Iron- 
glance,  or  fer  oligiste  of  the  French.  A 
sub-species  of  rhomboidal  iron  ore,  com- 
prising two  varieties,  viz.  the  common, 
occurring  in  beds  in  primitive  moun- 
tains, and  affording  an  excellent  malle- 
able iron  ;  and  the  micaceous,  found  in 
beds  in  mica  slate,  and  yielding  an  iron 
well  suited  for  cast  ware. 

SPE'CULUM.  The  Latin  term  for  a 
looking-glass  ;  a  name  frequently  given 
to  a  mirror  used  for  any  scientific  pur- 
pose, as  in  a  reflecting  telescope.  See 
Mirror. 

SPECULUM  METAL  {speculum,  a 
looking-glass).  An  alloy  of  about  two 
310 


parts  of  copper  and  one  of  tin  ;  used  for 
making  mirrors. 

SPEISS.  An  artificial  arseniuret  of 
nickel,  containing  about  54  per  cent,  of 
nickel.  It  collects  at  the  bottom  of  cru- 
cibles in  which  smalt  or  cobalt  blue  is 
prepared. 

SPELTER.  The  name  by  which  zinc 
is  known  in  commerce;  but  it  usually 
contains  some  lead  and  sulphur. 

SPERMATOCYSTI'DIUM  (<nrepna, 
a  seed,  kvctk,  a  bladder).  The  name 
given  by  Hedwig  to  the  male  organ  of 
mosses  ;  it  is  a  pedunculated  oblong  sac, 
containing  a  fluid  mixea  with  a  granular 
pulp,  which  is  discharged  with  some 
force  from  the  sac  on  the  application  of 
water.  By  other  writers  these  bodies  are 
called  staminidia  or  antheridia. 

SPERMATO'PHORA  (airep/ua,  seed, 
0epw,  to  carry).  The  cylindrical  capsules 
or  sheaths  in  the  cephalopods  which  con- 
vey the  sperm.  They  are  also  called  the 
moving  filaments  of  Needham,  their  dis- 
coverer. 

SPERMATOZO'A  (vwepua,  seed, 
£u>ov,  an  animal).  Zoosperms,  or  ani- 
malcules found  in  the  vas  deferens  and 
the  vesiculae  seminales  of  animals,  and, 
it  is  said,  in  cryptogamic  plants,  and  in 
the  pollen  grains  of  the  higher  orders  of 
plants. 

SPE'RMODERM  (anep/jia,  seed,  dep- 
ict, skin).  The  testa,  primine,  or  exter- 
nal membrane  of  the  seed  of  plants.  The 
term  is  sometimes  applied  collectively  to 
all  the  integuments  of  the  seed. 

SPH^RE'NCHYMA  («r0atpa,  a 
sphere,  e^xv^a,  any  thing  poured  in). 
Merenchyma.  The  name  given  by  Mor- 
ren  to  the  spherical  variety  of  the  paren- 
chyma of  plants. 

fcPHLEROSIDE'RITE.  Sparry  iron 
ore.  Carbonate  of  iron,  occurring  crys- 
tallized, fibrous,  massive,  and  botryoidal. 

SPH^E'RULITE  {ccpatpa,  a  sphere, 
\t'0os\  a  stone).  A  silicate  of  alumina, 
occurring  in  small  botryoidal  and  sphe- 
roidal masses,  imbedded  in  pitchstone, 
in  pearlstone,  &c. 

SPHALERO-CA'RPIUM  (<r0a\eP<ir, 
delusive,  napnos,  fruit).  A  botanical  de- 
signation of  the  collective  fruit  of  the 
yew,  blitum,  &c,  described  as  an  inde- 
hiscent,  one-seeded  pericarp,  enclosed 
within  a  fleshy  perianth.  This  is  the 
nux  baccata  of  authors. 

SPHE'CID/E  Sphegides.  A  family 
of  hymenopterous  insects  of  the  section 
Fossores,  named  from  the  typical  genus 
sphex,   one   species  of   which  has  been 


SPH 


SPI 


found  in  England,  but  appears  to  be  ex- 
tremely rare. 

SPHENE.  Prismatic  titanium  ore; 
a  silico-titanite  of  lime,  comprising  the 
common  and  the  foliated  varieties. 

SPHERE  {<T(patpa,  sphaera).  A  geo- 
metrical solid  described  by  the  revolution 
of  a  semicircle  about  its  diameter,  which 
remains  unmoved,  and  constitutes  the 
axis  of  the  sphere.  A  sphere  is  bounded 
by  a  curve  surface,  such  that  every  point 
thereon  is  situated  at  an  equal  distance 
from  a  point  within  the  solid  called  the 
centre.  The  diameter  of  a  sphere  is  any 
straight  line  which  passes  through  the 
centre,  and  is  terminated  both  ways  by 
the  superficies  of  the  sphere. 

1.  The  term  Sphere  is  applied,  in  astro- 
nomy, to  the  great  concavity  formed  by 
the  space  surrounding  our  globe,  in 
which  we  see  the  celestial  bodies.  It 
appears  to  revolve  upon  the  two  poles. 

2.  Those  places  with  respect  to  which 
the  poles  are  situated  in  the  horizon,  are 
said  to  have  a  right  position  of  the  sphere ; 
those  whose  horizon  coincides  with  the 
equator,  have  a  parallel  position  of  the 
sphere.  For  all  intermediate  places,  the 
position  is  oblique. 

3.  A  great  circle  of  a  sphere  is  that 
whose  plane  passes  through  the  centre  of 
the  sphere ;  it  divides  the  sphere  into 
two  equal  parts,  and  has  the  same  centre 
as  the  sphere  itself.  The  plane  of  a 
small  circle  does  not  pass  through  the 
centre  of  the  sphere. 

4.  Sphere,  doctrine  of  the.  An  expres- 
sion generally  signifying  the  application 
of  the  geometrical  notions  of  the  sphere 
to  geography  and  astronomy.  It  com- 
prises an  explanation  of  the  circum- 
stances under  which  spherical  trigono 
metry  is  applicable  to  these  two  sciences, 
and  the  nomenclature  which  is  employed 
to  facilitate  explanation. 

SPHE'RICAL  (<r<paipa,  a  sphere).  Re- 
lating to  a  sphere.  A  spherical  angle  is 
an  angle  formed  on  the  surface  of  a 
sphere  by  the  intersection  of  two  great 
circles,  or  circles  whose  planes  pass 
through  the  centre.  A  spherical  triangle 
is  a  triangle  formed  by  the  intersecting 
arcs  of  three  such  circles. 

SPHERICAL  EXCESS.  In  trigono- 
metry, this  denotes  the  sum  by  which 
the  three  angles  of  any  triangle  on  the 
surface  of  a  sphere  or  spheroid  exceeds 
two  right  angles. 

SPHERICS  (a<palpa,  a  sphere).  The 
doctrine  of  the  properties  of  the  sphere 
considered  as  a  geometrical  body,  and, 
311 


particularly,  of  the  different  circles  de- 
scribed on  its  surface. 

SPHEROID  (o-^cupct,  a  sphere,  ei3o?, 
likeness).  A  solid  body  approaching  to 
the  figure  of  a  sphere.  There  are  two 
kinds  of  spheroid,  the  oblate,  and  the  ob- 
long or  prolate,  the  former  shaped  like  an 
orange,  the  latter  like  a  lemon  ;  each 
may  be  supposed  to  be  described  by  the 
revolution  of  a  semi-ellipsis  round  its 
axis,  the  former  by  the  motion  of  the 
semi-ellipsis  round  its  lesser  axis,  the 
latter  by  the  ellipsis  divided  longwise, 
and  turned  round  the  greater  axis.  The 
earth  is  an  oblate  spheroid,  being  flat- 
tened at  the  poles.     See  Ellipsoid. 

SPHERO'METER  (aQalpa,  a  sphere, 
fjierpov,  a  measure).  An  instrument  for 
the  accurate  measurement  of  the  thick- 
ness of  small  bodies,  the  curvature  of 
optical  glasses,  &c. 

SPHE'RULA.  A  little -sphere;  a  term 
applied  to  the  globose  peridium  of  some 
fungaceous  plants,  having  a  central  open- 
ing through  which  sporidia  are  emitted, 
mixed  with  a  gelatinous  pulp. 

SPHFNGIDjE.  A  family  of  lepido- 
pterous  insects,  belonging  to  the  section 
Crepuscularia,  and  named  from  the 
genus  sphinx,  one  species  of  which  (atro- 
pos)  is  the  death's-head  hawk-moth,  of 
considerable  size,  and  not  uncommon  in 
some  parts  of  England. 

SPHRA'GIDE  (o-0pa7if,  a  seal).  Lem- 
nian  earth,  supposed  by  the  Turks  to 
possess  medicinal  virtue;  hence  it  was 
dug  up  by  them  with  religious  ceremo- 
nies, divided  into  spindle-shaped  pieces, 
and  stamped  with  a  seal. 

SPICA  VIRGINIS.  A  star  of  the 
first  magnitude  in  the  constellation 
Virgo. 

SPIKE.  A  form  of  inflorescence,  in 
which  all  the  buds  of  an  elongated 
branch  develop  as  flower-buds,  without 
forming  peduncles,  as  in  barley.  It  dif- 
fers from  a  raceme  merely  in  having  its 
flowers  sessile. 

SPIKELET.  Locusta.  A  small  spike  ; 
an  integral  portion  of  the  inflorescence 
of  wheat  and  other  grasses. 

SPINE  OF  PLANTS.  A  small  coni- 
cal projection,  consisting  of  a  hardened 
branch,  sometimes  bearing  leaves.  It 
differs  from  the  prickle  in  having  a  con- 
siderable quantity  of  woody  tissue  in  its 
structure,  and  in  being  as  much  in  com- 
munication with  the  central  parts  of  a 
stem  as  branches  them-elves. 

SPI  NELL.  Aluminate  of  magnesia; 
a  sub  species  of  octohedral  corundum,  of 


SPI 


SPO 


a  red  colour,  used  as  a  precious  stone. 
"When  it  weighs  four  carats  (about  16 
grains),  it  is  considered  of  equal 
value  with  a  diamond  of  half  the 
weight. 

SPINELLANE.  A  silicate  of  alu- 
mina, said  to  be  a  variety  of  Haiiyne, 
found  on  the  shores  of  the  lake  of  Laach, 
in  a  rock  composed  of  glassy  felspar, 
quartz,  hornblende,  &c. 

SPINI-CEREBRA'TA.  The  name 
given  by  Dr.  Grant  to  those  vertebrated 
animals,  of  which  the  central  parts  are 
in  the  form  of  a  lengthened  dorsal 
nervous  cord,  developed  anteriorly  into 
a  brain,  and  protected  by  a  vertebral 
column  and  cranium.  These  are  the 
myelencephala  of  Owen. 

SPI'NNARETS.  The  articulated  tubes 
with  which  spiders  construct  their  webs. 

SPINTHERE.  A  substance  supposed 
to  be  a  variety  of  sphene.  It  occurs  in 
the  department  of  Isere  in  France,  in- 
crusting  calcareous  spar  crystals. 

SPIRACLES  (spiraculum,  a  breathing 
hole).     The  breathing  pores  in  insects. 

SPIRAL  (ffTrelpa,  any  thing  rolled 
round  on  another  thing).  A  curve  which 
turns  round  like  a  circle,  but,  instead  of 
ending  where  it  began,  it  continues  to 
revolve,  receding  further  and  further 
from  the  centre,  like  the  spring  which 
moves  the  wheels  of  a  watch.  It  may  be 
briefly  described  as  a  curve  which  winds 
round  a  point  in  successive  convolu- 
tions. 

SPIRAL  VESSELS.  Trachenchyma. 
Long  cylindrical  tubes,  constituting  the 
vascular  tissue  of  plants.  Each  tube 
tapers  to  each  end,  and  has  an  elastic 
spiral  fibre  generated  within  it. 

SPIRE  (<T7reTpa,  a  coil  or  spiral  line). 
A  term  applied,  collectively,  to  the  con- 
volutions of  a  spiral  shell  which  are 
placed  above  the  lowest  or  body-whorl, 
whatever  shape  it  may  assume.  In  pla- 
norbis  the  spire  is  sunk  ;  in  cyprcea  it  is 
so  small  as  to  be  seen  only  when  the 
shell  is  young,  after  which  period  it  is 
covered  by  the  enlargement  of  the  body- 
whorl. 

SPIRIT.  A  general  term  for  all  in- 
flammable liquors  obtained  by  distilla- 
tion, now  almost  exclusively  applied  to 
spirit  of  wine  or  alcohol.  Ordinary  spirits 
contain  from  50  to  52  per  cent,  of  alcohol ; 
spirits  of  wine,  from  62  to  67  per  cent.  ; 
rectified  spirits,  from  82  to  85  per  cent. 

Spirit,  proof.  By  the  expression  that 
a  spirit  is  any  number,  say  ten,  over 
proof,  is  meant  that  100  gallons  of  the 
312 


spirit  would  bear  the  addition  of  ten 
gallons  of  water  to  reduce  it  to  proof 
strength,  or  it  would  form  110  gallons  of 
proof  spirit,  i.  e  spirit  of  density  0918633. 
The  term  ten,  under  proof,  means  that 
ten  gallons  of  water  must  be  taken  from 
100  gallons  of  the  spirit  to  raise  it  to 
proof,  or  that  100  gallons  of  it  contain 
only  90  gallons  of  proof  spirit. 

SPIRIT-LEVEL.  A  glass  tube  nearly 
filled  with  spirit  of  wine,  and  hermeti- 
cally sealed  at  both  ends.  The  exact 
horizontal  position  ofjts  axis  is  ascer- 
tained by  the  extremities  of  the  air- 
bubble  being  at  equal  distances  from  the 
middle  point  in  the  length  of  the  tube. 
The  level  is  used  for  determining  the 
relative  heights  of  ground  at  two  or 
more  stations. 

SPIRU'LIDjE.  A  family  of  poly- 
thalamous,  decapodous,  dibranchiate  ce- 
phalopods,  consisting  of  the  single  genus 
spirula,  and  named  by  Professor  Owen. 

SPODIUM  (<T7rod6?,  a  cinder).  A 
name  sometimes  given  to  the  oxide  of 
zinc,  which  sublimes  during  calcination. 

SPO'DUMENE.  Triphane.  Prismatic 
triphane  spar ;  a  silicate  of  lithia  and 
alumina,  found  in  embedded  crystalline 
masses. 

SPONDY'LIDjE.  A  natural  family  of 
marine  conchifers,  named  from  the  genus 
spondylus,  which  appears  to  be  co-exten- 
sive with  the  family  itself.  The  fossils 
of  this  family  are  very  numerous,  and  a 
somewhat  wide  geological  distribution. 
The  genus  plicatula  is  with  difficulty 
distinguished  from  spondylus. 

SPONGE  (spongia).  A  porous  sub- 
stance, generally  referred  to  the  class  of 
poriferous  animals.  The  sponge  of  com- 
merce is  the  dry  skeleton  of  the  animal, 
from  which  the  gelatinous  flesh  has  been 
removed. 

SPO'NGIOLE  or  SPONGELET  (spon- 
giola,  a  little  sponge).  The  absorbing 
extremity  of  the  fibril  of  a  root,  consist- 
ing of  extremely  lax  cellular  tissue  and 
mucus.  It  is  not  a  special  organ,  but 
merely  the  newly  formed  and  forming 
tender  tissue.  The  term  spongiole  is 
also  applied  to  the  warty  excrescence 
often  found  near  the  hilum  of  seeds,  and 
is  then  nearly  synonymous  with  stro- 
phiola. 

SPORANGFUM  (amopa,  a  spore,  a-y- 
7€tov,  a  vessel).  The  theca,  or  case, 
which  contains  the  spores  of  cryptogamic 
plants :  some  writers  consider  this  organ 
to  be  formed  by  the  adhesion  of  an  ex- 
ternal and  internal  series  of  organs,  the 


SQU 


ST  A 


Inner  series  being  called  sporangidium, 
to  which  the  peristomium  belongs.  A 
combination  of  sporangia  is  termed  by 
the  German  botanists  a  sporocarpium, 
especially  when  they  are  enclosed  in  a 
common  membrane. 

SPORE  (ffTropa,  a  seed).  Sporule. 
The  reproductive  body  in  cryptogamic 
plants,  analogous  to  the  seed  of  other 
plants,  but  differing  from  this  in  its 
mode  of  development  and  in  its  struc- 
ture ;  being  produced  apparently  without 
the  agency  of  sexes,  and  not  germinating 
from  any  fixed  point,  but  producing  its 
stem  and  root  indifferently  from  any 
points  of  its  surface. 

SPORI'DIA.  Granules  resembling 
sporules,  occurring  in  algaceous  plants, 
but  of  doubtful  nature.  In  fungaceous 
plants,  the  term  denotes  the  immediate 
covering  of  sporules.  Sporidiola  are  the 
sporules  themselves. 

SPRING.  A  piece  of  mechanism, 
formed  of  a  plate  of  steel  or  other  elastic 
substance,  employed  as  a  moving  power, 
or  as  a  regulator  of  the  motions  of  wheel- 
work  ;  also  for  the  purposes  of  producing 
resistance,  or  of  preventing  a  shock  from 
the  collision  of  hard  bodies.  In  the  form 
of  the  balance,  it  is  employed  as  a  means 
of  measuring  weight  or  force. 

SPUR.  Calcar.  The  name  given  to 
a  petal  which  is  lengthened  at  the  base 
into  a  hollow  tube,  as  in  orchis,  &c. 
This  is  sometimes  called  nectarotheca, 
though  frequently  without  reason. 

SQUA'LIDjE.  A  family  of  chondro- 
pterygious  fishes,  named  from  the  genus 
squalus,  and  including  the  various  spe- 
cies of  sharks. 

SQUAMA.  A  scale;  a  term  applied 
in  botany  to  any  kind  of  bract  which  has 
a  scaly  appearance.  A  diminutive  of  this 
is  squamula,  and  is  used  to  denote  each 
of  the  minute  hypogynous  scales  or 
bracts  found  within  the  outer  envelopes 
of  grasses. 

SQUA'MIPENNES  {squama,  a  scale, 
penna,  a  fin).  A  family  of  acanthoptery- 
gious  or  spiny -finned  fishes,  in  which 
the  soft  and  even  the  spinous  parts  of 
their  dorsal  fins  are  covered  with  scales, 
as  well  as  the  rest  of  their  body.  The 
chaetodon  may  be  taken  as  a  type  of  the 
family. 

SQUARE.  In  Geometry,  a  square  is 
a  plane  four-sided  figure,  with  all  its 
sides  equal,  and  all  its  angles  right;  or  it 
may  be  described  as  a  rectangle,  which 
has  two  adjoining  sides  equal.  In 
arithmetic  and  algebra,  a  square  signi- 
313 


fies  the  number  produced  by  multiplying 
a  number  by  itself.  The  reason  of  this 
double  use  of  the  word  '  square '  is  ob- 
vious: the  square  of  12  is  144,  and  this 
is  the  arithmetical  mode  of  finding  the 
content  of  a  square  of  12  units  in  length 
and  breadth  ;  but,  to  avoid  the  confusion 
occasioned  by  this  double  use  of  the 
word,  it  has  been  proposed  to  speak  of 
the  square  on  a  line  in  geometry,  and 
of  the  square  of  a  number  in  arithmetic 
and  algebra.     See  Power  of  Numbers. 

SQUARE  MEASURES.  Measures 
of  Superficies.  In  square  measure  the 
yard  is  divided,  as  in  general  measure, 
into  feet  and  inches,  144  square  inches 
being  equal  to  a  square  foot,  and  9  square 
feet  to  a  square  yard.  For  land  measure, 
the  multiples  of  the  yard  are  the  pole, 
the  rood,  and  the  acre;  the  pole  being 
equal  to  30J  square  yards,  the  rood  to 
40  poles,  the  acre  to  4  roods. 

SQUARE  NUMBER  ;  SQUARE 
ROOT.  A  square  number  is  the  product 
of  a  number  multiplied  by  itself,  as  25, 
the  square  of  5.  A  square  root  is  the  name 
of  a  number  with  reference  to  its  square, 
as  5,  the  square  root  of  25.  When  a  num- 
ber has  no  exact  root,  an  approximate 
root  may  be  found  by  the  usual  process 
of  extraction :  thus,  2  has  no  square  root, 
but  1.4142136  multiplied  by  itself,  is 
nearly  2,  and  is  therefore  the  square  root 
of  something  very  near  2. 

SQUARROSE.  A  term  applied,  in  de- 
scriptive botany,  to  parts  which  are 
spread  out  at  right  angles  from  a  com- 
mon axis,  as  the  leaves  of  some  mosses, 
the  involucra  of  some  compositae,  &c. 
By  squarrose-slashed,  as  applied  to  leaves, 
is  meant,  slashed  with  minor  divisions 
at  right  angles  with  the  other  divisions. 

STABLE  and  UNSTABLE.  These 
are  terms  employed  in  physics  in 
connexion  with  equilibrium  and  centre 
of  gravity.  Suppose  a  body  to  be  in  equi- 
librium under  the  action  of  any  forces ; 
let  the  body  be  arbitrarily  displaced  very 
slightly  from  the  position  of  equilibrium, 
then  if  the  forces  be  such  that  they  tend 
to  bring  the  body  back  to  its  position  of 
equilibrium,  the  position  is  stable ;  but  if 
they  tend  to  move  the  body  still  further 
from  the  position  of  equilibrium,  it  is 
unstable.  An  egg  will  rest  upon  its  side 
in  a  position  of  stable  equilibrium;  if 
placed  on  one  end,  it  will  be  in  a  position 
of  unstable  equilibrium. 

STAFF  A.  A  small  island,  lying  west 
of  the  larger  trap  masses  of  Mull,  en- 
tirely composed  of  amorphous  and  pil- 


ST  A 


STA 


lared  basalt,  the  pillars  being  generally 
arched  over  by  trap  rock  which  is  often 
prismatised  in  an  irregular  manner. 

STA'LACTITE  (<rra\af«>,  to  drop). 
Substances  found  suspended  from  the 
roof  of  mountain  caverns,  being  formed 
by  the  oozing  of  water  charged  with  cal- 
careous particles,  the  former  of  which 
evaporates,  leaving  the  latter  behind, 
which  hang  down  in  long  rods,  like 
icicles.  The  oriental  alabaster  appears 
to  be  of  stalactitic  origin. 

STA'LAGMITE  {araXay^i,  a  drop- 
ping). The  crust  composed  of  layers  of 
limestone,  which  is  formed  when  water 
holding  lime  in  solution  drops  on  the 
floor  of  a  cavern :  the  water  evaporates, 
the  lime  remains. 

STA'MEN  {<tt!]h<*v,  the  thread  of  the 
warp).  The  male  organ  of  flowering 
plants,  placed  immediately  inside  the 
petals,  and  constituting  collectively  the 
androceum,  or  male  apparatus  of  the 
flower.  The  stamen  consists  of  the 
filament,  the  anther,  and  the  pollen,  the 
first  of  which  is  not  essential :  a  stamen 
may  exist  without  a  filament,  but  it 
cannot  exist  without  an  anther  and  pol- 
len.    See  Adelphia. 

STAMINFDIA  {staminidium,  a  little 
stamen).  A  term  applied  to  small  sta- 
men-like organs  occurring  in  some  crypt- 
ogamous  plants.  These  are  the  sperma- 
tocystidia  of  Hedwig ;  they  are  found  in 
Jungermannia  and  in  some  species  of 
mosses,  but  no  analogy  of  function  to 
that  of  the  stamen  in  flowering  plants 
must  be  inferred  from  the  name. 

STANDARD.  Vexillum.  The  upper, 
erect,  and  expanded  petal  of  a  papiliona- 
ceous corolla. 

STANDARD  STARS.  The  name 
given  by  astronomers  to  those  stars  which 
are  best  known  and  best  adapted  for  ac- 
curate observation. 

STANNOUS  OXIDE  {stannum,  tin). 
Protoxide  of  tin.  Stannic  oxide  is  the 
peroxide  of  the  same  metal.  By  stan- 
nate,  is  meant  a  salt  of  tin  or  the  proto- 
chloride. 

STAR.  A  general  term  for  all  the 
heavenly  bodies.  In  Astronomy,  how- 
ever, there  are  several  classes  of  stars  : 
fixed  stars  are  those  which,  in  the  revo- 
lution oT-^he  sphere,  seem  always  to 
occupy  the  same  relative  position,  and 
to  preserve  the  same  distances  one  from 
another;  erratic  stars,  or  planets,  are 
those  which,  besides  the  daily  revolution, 
have  a  motion  peculiar  to  themselves, 
which  alters  their  relative  distances  from 
314 


the  other  bodies  around  them.  See 
Planet  and  Nebula. 

Binary  Stars.  By  this  term  are  de- 
noted sidereal  systems,  composed  of  two 
stars  revolving  about  each  other  in  regu- 
lar orbits  ;  the  individuals  are  equidistant 
from  the  eye ;  or,  at  least,  cannot  differ 
more  in  distance  than  the  semi-diameter 
of  the  orbit  they  describe  about  each 
other,  which  is  quite  insignificant  when 
compared  with  the  immense  distance 
between  them  and  the  earth.  These 
must  be  distinguished  from  the  double 
stars,  already  noticed,  in  which  these 
physically  connected  stars  are  con- 
founded, perhaps,  with  others  only  opti- 
cally double,  or  casually  juxtaposed  in 
the  heavens  at  different  distances  from 
the  eye.    Herschel. 

STARCH.  Fecula;  amylin.  An  organ- 
ized substance  separated  from  the  grains, 
roots,  and  stems  of  many  plants.  It  is 
contained  in  the  cavities  of  the  vege- 
table cells,  in  the  form  of  small,  white, 
and  brilliant  grains,  which  are  not  crys- 
talline, but  have  a  rounded  outline  with- 
out any  determinate  form.  Varieties  o 
this  substance  occur  in  arrow-root,  ami- 
din,  dextrin,  &c. 

STATICS  (o-TcrnKor,  causing  to  stand). 
That  division  of  the  science  of  mechanics 
which  relates  to  the  condition  of  bodies 
as  influenced  by  forces  which  are  in  equi- 
librium. Tt  thus  differs  from  the  other 
division,  or  Dynamics,  which  treats  of 
forces  which  produce  motion. 

1.  The  general  laws  of  Statics  and 
Dynamics  are  applicable  to  fluids ;  but, 
owing  to  the  peculiar  difficulty  attending 
the  consideration  of  this  class  of  bodies, 
they  are  generally  treated  separately,  that 
part  of  the  mechanics  of  fluids  which 
relates  to  equilibrium  being  termed  hy- 
drostatics, while  that  which  investigates 
their  motion  is  termed  hydrodynamics. 

2.  Statical  figure.  The  figure  which 
results  from  the  equilibrium  of  forces. 

STATION.  A  technical  term  em- 
ployed in  botanical  language  to  denote 
the  peculiar  nature  of  the  locality  where 
each  species  of  plants  is  accustomed  to 
grow,  and  it  has  reference  to  climate, 
soil,  humidity,  light,  elevation  above  the 
sea,  and  other  analogous  circumstances. 
See  Habitation. 

STATIONARY.  This  term  is  applied 
by  astronomers  to  the  condition  of  a 
planet,  so  far  as  visible  motion  is  con- 
cerned. The  planets  move  sometimes 
from  west  to  east,  sometimes  from  east 
to  west,  but  much  more  in  the  former 


STE 


STE 


than  in  the  latter  direction,  so  that  they 
may  be  said  to  progress  with  occasional 
retrogradations.  The  end  of  each  kind 
of  motion  and  the  beginning  of  the  next 
is  performed  with  such  extreme  slow- 
ness, that  for  several  days  together  the 
planet  does  not  seem  to  change  its  place 
among  the  stars  at  all,  whence  it  is  said 
to  be  stationary,  i.  e.  so  far  as  we  can 
trace  its  motion. 

STATISTICS.  That  department  of 
political  science  which  relates  to  the 
investigating  and  the  arranging  of  facts 
illustrative  of  the  actual  condition  and 
resources  of  a  state.  It  is  the  basis 
upon  which  the  statesman  and  the  poli- 
tical economist  reason,  and  from  which 
they  draw  conclusions. 

Medical  statistics  consists  in  the  ap- 
plication of  numbers  to  illustrate  the 
natural  history  of  men  in  health  and 
disease. 

STAU'ROLITE  (o-raupos,  a  cross,  Xi- 
0oc,  a  stone).  Staurotide.  A  bisilicate 
of  alumina  and  of  oxide  of  iron,  called 
also  granatite  and  cross-stone,  among  the 
specimens  of  which  are  the  fine  mackled 
crystals  from  Britany,  and  the  modifica- 
tions of  the  simple  crystals  from  St. 
Gothard,  accompanied  by  prisms  of  dis- 
thene,  perfectly  similar  to  those  of  the 
staurolite,  and  sometimes  longitudinally 
grown  together  with  them. 

STEAM.  The  vapour  of  water  raised 
to  a  high  degree  of  elasticity  by  heat. 
When  raised  at  the  ordinary  tempera- 
ture, it  is  termed  low-pressure  steam; 
when  heat  is  applied  to  ordinary  steam, 
under  a  constant  bulk,  its  elasticity 
rapidly  increases,  and  it  is  then  termed 
high-pressure  steam. 

STEAM  ENGINE.  There  are  two 
kinds  of  steam  engine  in  general  use, 
the  low-pressure  and  the  high-pressure 
engine.     See  Steam. 

1.  The  term  low-pressure  engine  is  not 
in  all  cases  correct,  for  many  of  these 
engines,  particularly  those  which  com- 
bine expansion  with  condensation,  work 
with  a  considerable  load  on  the  safety- 
valve,  as  in  the  case  of  the  Cornish 
engines.  But  the  term  condensing  engine 
always  , conveys  a  true  impression,  viz. 
that  the  engine  is  provided  with  a  con- 
densing apparatus. 

2.  The  terms  high-pressure  engine  and 
non-condensing  engine  are  equally  sig- 
nificant: such  engines,  having  no  con- 
densing apparatus  for  the  production  of  a 
vacuum,  are  obliged  to  work  with  steam 
of  higher  pressure  than  that  of  the  atmo- 

315 


sphere.  The  essential  parts  of  a  high- 
pressure  engine  are  only  two  in  number, 
the  boiler  and  the  cylinder;  the  low- 
pressure  engine  requires  the  presence  of 
a  third  part,  the  condenser. 

3.  Classification  of  Engines.  The  fol- 
lowing classification  of  the  various  steam 
engines,  according  to  the  principles  by 
which  they  are  worked,  may  be  found 
convenient  as  a  table  of  reference : 

I.  Condensing  Steam  Engines. 

1.  Simple  condensation  in  the  cylinder. 

Atmospheric  engines. 

2.  Simple  condensation  in  the  condenser. 

1.  Watt's  single-acting  engines. 

2.  Watt's  double-acting  engines. 

3.  Cornish  single-acting  engines. 

3.  Condensation  and  expansion. 

1.  Expansion  in  one  cylinder. 

1.  Watt's  engines,  single  and  double. 

2.  Cornish  engines,  single  and  double. 

2.  Expansion  in  two  cylinders. 

Hornblower's  and  Woolf  s  engines. 

II.  N on- condensing  Steam  Engines. 

1.  Simple  generation  of  steam. 

2.  Generation  and  expansion  of  steam. 
STE'ARIC  ACID   (areap,  suet).    An 

acid  procured  from  animal  and  vegetable 
fats,  and  from  the  bile  of  many  animals. 
Stearine  is  a  solid  crystallizable  sub- 
stance, the  essential  part  of  all  kinds  of 
suet.  Stearopten  is  the  solid  portion  of  a 
volatile  oil,  as  distinguished  from  elaop- 
ten,  or  the  liquid  portion. 

STE'ATITE  (o-reap,  suet).  Another 
name  for  soapstone,  derived  from  its 
greasy  feel.  It  may  easily  be  cut  with  a 
knife,  and  yields  even  to  impressions  of 
the  nail.  The  most  remarkable  varieties 
are,  that  of  a  yellowish-green  colour  from 
Greenland,  and  that  from  Gbpfersgriin 
in  Baireuth,  with  small  crystals  of  other 
mineral  substances,  especially  quartz, 
converted  into,  and  forming  part  of,  the 
massive  steatite ;  a  variety  called  chalk 
of  Briancon,  &c. 

STEEL.    Carburetted  iron;  the  aver- 
age proportion  of  carbon  is  supposed  to 
amount  to  ^  part.    The  different  tem- 
pers, or  degrees  of  hardness,  of  rigidity, 
or  of   elasticity  of    steel  are   given  by* 
means  of  the  different  degrees  of  heat  to  I 
which  the  metal  is  exposed  in  the  opera- 1 
tion.  ' 

STE  EL- YARD.  The  steel-yard  differs 
from  the  balance,  in  having  its  support 
near  one  end,  instead  of  in  the  middle; 
and  also  in  having  the  weights  suspended 


STE 


STI 


by  hooks,  instead  of  being  placed  in  a 
dish. 

STEINHEILITE.  Blue  quartz;  a 
variety  of  iolite,  from  Orayervi  in  Fin- 
land. 

STELLA'TjE  (stella,  a  star).  Ga- 
liacece.  The  Madder  tribe  of  dicotyle- 
donous plants,  characterized  by  their 
square  stems,  and  by  their  verticillate 
leaves  without  stipules,  presenting  a 
star-like  appearance. 

STELLE'RIDjE  (stella,  a  star).  A 
family  of  anenterous  echinoderms,  in 
which  the  radiated  form  is  most  complete 
and  general,  and  in  which  the  species 
have  consequently  received  the  common 
appellation  of  star-fishes,  or  sea-stars. 
They  constitute  the  third  order  of  the 
Actinozoaria  of  De  Blainville. 

STENELY'TRANS  (<rTewk,  narrow, 
eXvrpov,  a  wing-case).  A  family  of  cole- 
opterous insects,  comprising  those  in 
which  the  elytra  become  narrow  at  the 
posterior  part  of  the  body. 

STENO'GRAPHY  (crrevof,  contracted, 
ypd<p(o,  to  write).  Brachygraphy.  The 
art  of  short-writing,  or  the  representa- 
tion of  words  by  means  of  a  few  simple 
characters.  Various  modes  of  steno- 
graphy have  been  successively  employed ; 
the  best  is  that  which  employs  the  fewest 
arbitrary  signs. 

STEPPES.  A  Russian  name  applied 
particularly  to  the  extensive  plains  which 
lie  on  the  north-west  of  Asia.  The  greater 
part  of  what  is  properly  called  the  steppes 
forms  a  considerable  portion  of  the  coun- 
try known  as  Independent  Tartary. 

STERELMI'NTHA  (arepeor,  solid, 
tXjiuvv,  an  intestinal  worm).  Intestinal 
worms  which  have  no  true  abdominal 
cavity,  as  the  tape-worm.  These  are  the 
parenchymatous  entozoa  of  Cuvier. 

STEREOGRA'PHIC  (trrepeor,  solid, 
7pa0o>,  to  write).  The  term  applied  to 
that  mode  of  projecting  a  sphere  upon  a 
plane,  in  which  the  eye  is  at  a  point  in 
the  sphere,  and  the  plane  of  projection 
is  the  great  circle  of  which  the  eye  is  at 
the  pole,  or  a  plane  parallel  to  it.  See 
Projection. 

STEREO'METER  (arepeor,  solid,  ^- 
rpov,  a  measure).  An  instrument  for 
determining  the  specific  gravity  of  liquid, 
porous,  and  pulverulent,  as  well  as  of 
solid  bodies. 

STE'REOSCOPE  (tr-repebt,  solid,  <tko- 
TTfw,  to  see).  An  instrument  consisting 
of  two  plane  mirrors,  inclined  with  backs 
to  each  other,  at  an  angle  of  90°;  per- 
spective drawings  of  an  object  are  placed 
316 


at  the  sides  of  the  mirrors,  and  at  equal 
distances  from  them  in  the  same  hori- 
zontal line ;  the  spectator  placing  his  head 
against  the  edges  of  the  two  mirrors, 
will  see  a  single  image  of  the  solid  repre- 
sented by  the  drawings. 

STE'REOTYPE  (trrepeo?,  solid,  two?, 
a  type).  The  art  of  printing  from  cast 
plates  of  type  metal,  instead  of  from 
moveable  types. 

STERNO'XI  (arepvov,  sternum,  6?i»?, 
sharp-pointed).  A  tribe  of  coleopterous 
insects,  in  which  the  sternum  is  pro- 
longed into  a  point  at  both  extremities. 

STIBIUM.  The  old  name  for  the  ore 
of  antimony.  Hence  we  meet  with  the 
terms  stibious  and  stibic,  for  the  anti- 
monious  and  the  antimonic,  acids. 

STIGMA  (o-ti'Co),  to  prick).  The  upper, 
spongy,  and  secreting  extremity  of  the 
style  in  plants.  From  its  property  of 
absorbing  the  fecundating  matter  con- 
tained in  the  pollen-grain,  it  has  been 
termed  the  pistillary  spongelet. 

STILBITE.  A  crystallized  simple 
lustrous  mineral,  usually  white,  one  of 
the  zeolite  family,  frequently  included  in 
the  mass  of  the  trap  rocks.  It  corre- 
sponds in  composition  with  felspar,  but 
contains  in  addition  6  atoms  of  water. 

STILPNOSIDE'RITE.  A  mineral 
allied  to  meadow  iron-ore,  said  to  con- 
tain phosphoric  acid,  occurring  together 
with  brown  iron  in  Saxony  and  Bavaria. 

STING  OF  PLANTS.  A  modifica- 
tion of  the  hair  of  plants,  stiff  and  pun- 
gent, giving  out  an  acrid  juice  when 
touched,  as  in  nettle. 

STINKSTONE.  Swinestone.  A  va- 
riety of  compact  lucullite  (a  sub-species 
of  limestone),  emitting  a  fetid  odour  on 
friction.  It  occurs  in  beds  in  secondary 
limestone,  alternating  occasionally  with 
secondary  gypsum  and  beds  of  clay. 

STIPES.  A  term  applied  to  the  sUm 
of  endogenous  trees,  to  the  stalk  which 
supports  the  pileus  of  the  mushroom, 
&c. 

STI'PITATE  {stipes,  a  stalk).  Stalked; 
that  which  is  furnished  with  a  stalk,  as 
the  pappus  of  some  composite  plants. 
The  term  does  not  apply  to  the  petiole  of 
a  leaf,  or  to  the  peduncle  of  a  flower. 

STIPULE  {stipula,  the  husk  of  straw). 
A  small  leaf-like  organ,  attached  to  the 
base  of  the  petiole  of  the  leaf  in  many 
plants.  In  pinnate  leaves  there  is  often 
a  pair  of  stipules  at  the  base  of  eacli 
leaflet,  as  well  as  two  at  the  base  of  the 
common  petiole;  the  subordinate  pairs 
are  called  stipels.    Hence  the  terms  sti' 


STR 

palate,  furnished  -with  stipules;  and 
exstipulate,  having  no  stipules. 

STOLE  (stolo,  a  shoot  or  scion).  By 
this  term  some  botanists  have  designated 
that  kind  of  branch  of  plants,  which 
differs  from  the  soboles  or  sucker  in  pro- 
ceeding from  the  stem  above  the  surface 
of  the  earth,  into  which  it  afterwards 
descends  and  takes  root,  as  in  aster 
junceus.  By  the  older  botanists,  a 
sucker  was  always  understood  by  the 
word  stolo,  and  surculus  indicated  a 
vigorous  young  shoot  without  branches. 

STOMA'PODA  {aropa,  a  mouth,  now, 
wo36r,  foot).  A  group  of  the  Crustacea, 
in  which  the  cephalic  segment  is  free, 
and  supports  large  pediform  maxillae. 
In  these  animals  the  branchiae  are  at- 
tached to  natatory  post-abdominal  feet. 

STO'MATE  (ffTo/ia,  a  mouth).  The 
botanical  name  for  an  oval  space,  lying 
between  the  sides  of  the  cells  in  the  epi- 
dermis of  plants,  and  opening  into  a 
cavity  in  the  subjacent  tissue. 

STONESFIELD  SLATE.  Slaty  cal- 
careous limestone ;  a  constituent  portion 
of  the  Lower  Oolite  formation,  abound- 
ing in  organic  remains. 

STOOL  (stolo,  a  shoot  or  scion).  A 
term  applied  in  Botany  to  the  parent 
plant  from  which  young  individuals 
are  propagated  by  the  process  of  layer- 
ing, as  it  is  technically  called  by  bo- 
tanists. 

STOURBRIDGE  CLAY.  A  variety 
of  clay  with  the  general  properties  of 
potters'  clay,  but  of  a  dark  colour,  em- 
ployed in  the  manufacture  of  crucibles. 
It  appears  to  have  originated  from  the 
disintegration  of  shale. 

STRAIGHT  LINE.  According  to 
Plato's  definition,  "  a  straight  line  is  that 
of  which  the  middle  parts  hide  the  ex- 
tremities," the  eye  being  placed  in  the 
continuation  of  the  line.  Archimedes 
defined  a  straight  line  as  "  the  shortest 
distance  between  two  points."  Euclid 
defines  it  as  "  that  which  lies  evenly  be- 
tween its  extreme  points."  These  are 
all  very  amusing  definitions  Jo  those  who 
Jcnow  what  a  straight  line  isT"for  Tfie 
rest,  it  may  be  sufficient  to  say  that  "  a 
straight  line  is  a  straight  line." 

STRAIT.  A  narrow  channel  connect- 
ing two  seas  together,  or  a  sea  with  the 
ocean,  as  the  strait  of  Gibraltar. 

STRATIFIED  ROCKS.  Rocks  ar- 
ranged in  strata  or  beds,  supposed  to 
have  been  so  deposited  by  water.  Under 
the  terms  Primary,  Secondary,  and  Ter- 
tiary Strata,  the  characters  of  these  rocks 
317 


STR 

are  described.    Other  particulars  willoe 
found  under  the  term  Stratum. 

STRATUM  {stratum,  a  layer  or  bed, 
from  sterno,  to  spread  out).  In  the  lan- 
guage of  Geology,  a  stratum  is  a  bed  or 
mass  of  matter  spread  out  over  a  certain 
surface  by  the  action  of  water,  or,  in 
some  cases,  by  wind.  The  deposition  of 
successive  layers  of  sand  and  gravel  in 
the  bed  of  a  river,  or  in  a  canal,  affords  a 
perfect  illustration  both  of  the  form  and 
the  origin  of  stratification.  A  large  por- 
tion of  the  masses  constituting  the  earth's 
crust  are  thus  stratified,  the  successive 
strata  of  a  given  rock  preserving  a  gene- 
ral parallelism  to  one  another ;  but  the 
planes  of  stratification  are  not  perfectly 
parallel  throughout  a  great  extent,  like 
the  planes  of  cleavage.    See  Rock. 

1.  The  inclination  of  strata  from  the 
horizontal  position  is  called  the  dip.  The 
direction,  or  line  of  bearing,  of  strata  is 
called  the  strike,  and  it  is  indicated  by  a 
horizontal  line  at  right  angles  to  the  dip. 
When  strata  protrude  above  the  surface, 
or  appear  uncovered,  they  are  said  to 
crop  out.  They  are  said  to  be  conform- 
able, when  their  planes  are  parallel,  what- 
ever their  dip  may  be;  unconformable, 
when  a  set  of  strata  is  so  connected  with 
another,  that  the  planes  of  stratification 
of  the  one  series  have  a  different  direc- 
tion from  those  of  the  other  series.  See 
Fault. 

2.  Strata,  recent  or  alluvial.  Under 
this  term  are  included  all  those  deposits 
which  have  resulted  from  the  action  of 
the  elements,  or  from  the  progress  of 
vegetation,  in  the  course  of  the  period 
which  has  commenced  after  the  depo- 
sition of  the  tertiary  strata,  and  has  con- 
tinued to  the  present  day.  They  may  be 
arranged  under  the  heads  of  alluvial  de- 
posits, concretionary  deposits,  coralline 
deposits,  and  vegetable  deposits.  These 
terms  will  be  found  in  their  respective 
places. 

STRATUS  (Lat.  a  bed  or  covering). 
The  fall-cloud ;  a  primary  foirni  of  cloud, 
which  rests  upon  the  surface  of  the  earth. 
It  varies  in  extent  and  thickness,  and  is 
generally  formed  by  the  subsidence  of 
vapour  in  the  atmosphere.  This  form 
comprises  all  those  fogs  and  mists  which, 
on  summer  evenings,  fill  the  valleys, 
remain  during  the  night,  and  disappear 
in  the  morning.  Hence  it  has  been  called 
the  cloud  of  night.  The  stratus  must  be 
distinguished  from  that  variety  of  the 
cirro-stratus  which  resembles  it  in  exter- 
nal characters :  the  former  does  not  wet 
P3 


STR 

im  objects  on  which  it  alights ;  the  latter 
moistens  every  thing  it  touches. 

STREAM-MEASURER.  An  instru- 
ment for  measuring  the  velocity  of  a 
stream  of  water  at  different  depths.  One 
of  the  simplest  is  Pictot's  tube ;  it  con- 
sists of  a  tube  bent  nearly  at  a  right 
angle,  expanding  in  a  funnel  shape; 
this  is  placed  into  the  direction  of  the 
stream  ;  the  upper  part  above  the  water 
must  be  of  glass.  If  the  water  be  in  a 
state  of  rest,  the  level  within  and  with- 
out the  tube  will  be  equal ;  but  if  it  be 
in  motion,  the  impulse  of  the  stream 
will  cause  a  column  of  the  fluid  to  ascend 
until  the  weight  of  this  column  become 
a  counterpoise  to  the  force  with  which 
the  water  is  impelled. 

STREAM  TIN.  Tinstone,  or  native 
oxide  of  tin,  occurring  in  rounded  par- 
ticles and  masses  mixed  with  other  allu- 
vial matters.  The  finest  grain  tin  is  pro- 
cured from  this  ore. 

STREPS I'PT ERA  (arpevr6^  twisted, 
irrepbv,  a  wing).  A  singular  order  of 
Insects  discovered  by  Mr.  Kirby,  in 
which  the  anterior  wings  are  reduced  to 
minute  appendages  twisted  spirally. 

STRI'ATED  {stria,  a  streak).  Marked 
with  very  slender  lines,  or  strice,  either 
indented  or  elevated,  at  parallel  and 
nearly  equal  distances.  When  the  lines 
are  deeper  than  striae,  and  indented,  they 
are  called  grooves ;  when  still  deeper 
and  elevated,  ridges. 

STRFGID.E  (strix,  the  screech-owl). 
The  Owl  tribe ;  a  family  of  the  JRaptores, 
or  Rapacious  birds,  including  all  the  noc- 
turnal birds  of  prey,  and  characterized 
by  the  large  proportion  of  the  head  to  the 
body,  and  by  the  size  of  the  eyes,  which 
are  surrounded  by  a  fringe  of  feathers, 
most  remarkable  in  the  barn  owl  and  its 
allies. 

STRI'GOSE  (strigosus,  scraggy).  A 
term  applied  to  a  surface  covered  with 
sharp,  appressed,  rigid  hairs ;  a  term 
synonymous  with  hispid. 

STRO'BILE  (orpo/fc'Xn,  a  plug  of  lint 
twisted  into  an  oval  shape  like  a  pine- 
cone).  Cone.  An  amentiform  fruit,  the 
carpels  of  which  are  scale-like,  spread 
open,  and  bear  naked  seeds  ;  sometimes 
the  scales  are  thin,  with  little  cohesion, 
as  in  the  hop  ;  but  they  are  often  woody, 
and  cohere  into  a  single  tuberculated 
mass,  as  in  the  pine.     See  Galbulus. 

STROBOSCO'PIC  PLATES  (<rTp6/3o9, 

a  whirling  round,   arKoneu),  to  observe). 

An  apparatus  invented  by  Stampfer  of 

Vienna,  by  which  an  impression  is  pro- 

318 


STR 

duced  on  the  retina  of  an  uninterrupted 
line  of  light  by  the  rapid  motion  of  a 
luminous  object.  On  the  same  principle 
is  explained  the  action  of  the  thauma- 
trope,  and  of  Newton's  coloured  wheels. 

STRO'MA.  A  fleshy  body  occurring 
in  fungaceous  plants,  to  which  flocci  are 
attached,  as  in  isaria,  &c 

STRO'MBIDvE.  Wing-shells  ;  a  fa- 
mily of  carnivorous  Gasteropods,  named 
from  the  typical  genus  strombus ;  the 
outer  side  or  lip  of  the  aperture  is  con- 
siderably dilated.  * 

STRO'MBIN^.  The  true  Wing- 
shells  ;  a  sub-family  of  the  Strombidez, 
having  the  outer  lip  greatly  dilated,  with 
a  lobe  at  the  base,  and  often  on  the  sum- 
mit also  of  the  outer  lip ;  the  spire  being 
always  more  or  less  elevated. 

STRO'NTIANITE.  Carbonate  of 
strontia;  a  mineral  of  fibrous  texture, 
sometimes  transparent  and  colourless, 
but  generally  with  a  tinge  of  yellow  or 
green. 

STRO'NTIUM.  The  metallic  base  of 
the  alkaline  earth  strontia,  named  from 
Strontian,  a  mining  village  in  Argyle- 
shire.  The  earth  strontia  is  to  barytes, 
what  soda  is  to  potash.  Sulphate  of 
strontia  is  known  as  celestine,  and  occurs 
in  regular  crystals  of  the  same  form  as 
sulphate  of  barytes. 

STRO'PHIOL^.  Carunculce.  Irre- 
gular protuberances  sometimes  occurring 
about  the  umbilicus  of  seeds;  in  such 
cases,  the  umbilicus  is  said  to  be  stro- 
phiolate  or  carunculate. 

STRUCTURE  OF  ROCKS.  The 
structure  of  rocks  relates  to  the  arrange- 
ment of  their  parts,  viewed  on  a  larger 
scale  than  that  of  their  texture.  Struc- 
ture is  said  to  be  massive,  when  the  rock 
presents  no  internal  division  into  plates, 
prisms,  or  balls,  but  is  of  a  uniform  tex- 
ture over  a  great  extent ;  prismatic  or 
columnar,  when  a  mass  of  a  rock  is  inter- 
nally divided  by  fissures  into  prisms  of 
various  sizes  or  forms,  as  in  basalt, 
greenstone,  and  porphyry ;  tabular,  when 
a  rock  is  composed  of  parallel  plates, 
separated  by  regular  seams ;  globular, 
when  globular  masses  of  large  size  are 
imbedded  in  a  substance  of  the  same 
nature. 

STRUMA.  Bourrelet.  A  dilatation 
of  the  petiole  of  a  leaf,  at  the  extre- 
mity where  it  is  connected  with  the 
lamina.  Also,  a  dilatation  at  tne  base  of 
the  sporangium  of  mosses. 

STRUTHIO'NID^  {struthio,  the 
ostrich).    A  natural  family  of  terrestrial 


STY 


SUB 


birds,  comprising  the  ostrich,  the  cas- 
sowary, the  dodo,  the  emu,  the  apterix, 
&c.  In  these  birds  the  locomotive  power 
resides  in  the  lower  extremities,  the 
wings  being,  in  the  majority  of  cases, 
merely  rudimentary. 

STRYCHNINE.  Strychnia.  An  al- 
kali derived  from  the  Nux  Vomica  class 
of  plants,  and  particularly  from  the  seeds 
of  the  Strychnos  nux  vomica,  and  St.  Ig- 
natius's  bean,  the  fruit  of  Strychnos  igna- 
tia.  Strychnine  exists  in  these  plants  in 
combination  with  strychnic  acid. 

STU'CCO.  Sulphate  of  lime  ;  an  arti- 
ficial hydrate,  having  the  same  compo- 
sition as  native  gypsum.  When  made 
into  a  paste  with  water,  it  forms  a  hard 
coherent  mass,  or  sets,  in  a  minute  or 
two,  with  a  slight  evolution  of  heat. 

STUFAS.  Jets  of  steam  issuing  from 
fissures  in  volcanic  regions  at  a  tempera- 
ture of  ten  above  the  boiling  point. 

STURIO'NES  {sturio,  the  sturgeon). 
The  Sturgeon  tribe ;  an  order  of  carti- 
laginous fishes,  in  which  the  gills  hang 
freely,  and  are  covered  with  a  gill-lid 
having  a  single  wide  opening,  as  in  the 
osseous  fishes.  In  these  fishes  a  large 
swimming-bladder  exists,  from  which  is 
obtained  the  valuable  material  called 
isinglass. 

STU'RNIDjE  (sturnus,  the  starling). 
The  Starling  tribe,  placed  by  Vigors  be- 
tween the  Fringillidae  and  the  Corvidae, 
in  his  Conirostres. 

STYLE  {aTv\ti,  a  pillar).  In  Botany, 
that  elongation  of  the  ovary  which  sup- 
ports the  stigma.  It  is  frequently  ab- 
sent, and  then  the  stigma  is  sessile  on 
the  ovary.  It  is  not  more  essential  to  a 
pistil  than  a  petiole  to  a  leaf,  a  claw  to  a 
petal,  or  a  filament  to  the  stamen. 

STYLE,  OLD  and  NEW.  By  the  Old 
Style  is  meant  the  method  of  computing 
time  anterior  to  the  reformation  of  the 
calendar  by  Pope  Gregory  XIII;  and  by 
the  New  Style,  that  which  has  been  in 
use  since.  The  reformation  took  place 
in  1582,  in  which  ten  days  were  deducted 
from  the  year,  by  calling  what,  according 
to  the  old  calendar,  would  have  been  the 
5th  of  October,  the  15th  of  October,  1582. 
From  thence  to  the  end  of  February,  1700, 
new  style  is  ten  days  in  advance  of  old 
style  :  thus  January  1  (O.  S.)  is  January 
11  (N.  S.)  and  so  on.  From  and  after 
March  1,  1700,  to  the  end  of  February, 
1800,  new  style  is  eleven  days  in  advance 
of  old  style:  thus  January  1  (O.  S.)  is 
January  12  (N.  S.).  The  new  style  was 
applied  in  England  in  1751. 
319 


STYLOSTE'GIUM  (<nv\n>  the  style, 
o-Tf7&),  to  cover  closely).  Orbiculus.  The 
botanical  name  of  a  peculiar  appendage 
of  the  petals  found  in  certain  plants,  also 
called  corona.  In  narcissus,  it  forms  an 
undivided  cup,  surrounding  the  stamens 
and  style.  When  divided,  its  parts  bear 
various  names,  as  horns,  beak,  wings, 
folioles,  &c. 

STYRA'CEjE.  The  Styrax  tribe  of 
dicotyledonous  plants.  Trees  or  shrubs 
with  leaves  alternate ;  flowers  monope- 
talous  ;  stamens  of  unequal  length ;  ovary 
superior,  containing  cells ;  fruit  drupa- 
ceous. 

SUB-.  A  Latin  preposition,  denoting, 
1.  a  position  beneath  any  body ;  2.  a 
slight  modification,  corresponding  to  the 
English  term  somewhat,  as  in  sub-ovate, 
somewhat  ovate,  sub-viridis,  somewhat 
green ;  and  3.  in  chemical  terms,  an  in- 
termediate degree  of  oxidation,  as  in  sub- 
sulphurous  acid,  or  that  which  is  inter- 
mediate between  the  sulphurous  and 
hyposulphurous  acids. 

1.  Sub-altern.  In  Logic,  Subaltern 
Species  and  Genus  is  that  which  is  both 
a  species  of  some  higher  genus,  and  a 
genus  in  respect  of  the  species  into  which 
it  is  divided.  Subaltern  Opposition  is 
between  a  universal  and  a  particular  of 
the  same  quality;  of  these,  the  univer- 
sal is  the  subalternant,  and  the  particular 
the  subalternate. 

2.  Sub-Apennines.  Low  hills  which 
skirt,  or  lie  at  the  foot  of,  the  great  chain 
of  the  Apennines  in  Italy.  This  term  is 
applied  by  geologists  to  a  series  of  strata 
of  the  old  Pliocene  period. 

3.  Sub-contrary.  In  Mathematics, 
when  a  figure  or  solid  is  symmetrical,  so 
that  equal  lines  or  polygons  can  be  drawn 
on  two  different  sides,  those  equal  lines 
or  polygons  may  be  termed  sub-contrary. 
The  two  equal  sides  of  an  isosceles  tri- 
angle are  sub-contrary.  In  a  right  cone, 
every  section  has  its  sub-contrary,  ex- 
cept only  the  circle  which  generates  the 
cone,  and  its  parallels. 

4.  Sub-contrary  opposition.  This  oc- 
curs, in  Logic,  between  two  particular 
propositions,  the  affirmative  and  the  ne- 
gative. Both  are  true  in  contingent  mat- 
ter, but  never  both  false.    See  Opposition. 

5.  Sub-dominant.  In  Music,  a  kind  of 
governing  note,  being  the  fifth  below  the 
key-note.  In  the  regular  ascending  scale 
of  seven  notes,  it  is  the  fourth :  thus,  in 
the  key  of  C,  F  is  the  sub-dominant ;  the 
term,  however,  is  derived  from  the  relation 
of  the  note  to  the  tonic  as  the  fifth  below. 

P4 


SUB 


SUB 


6.  Sub-duplicate.  In  Arithmetic  and 
Algebra,  the  sub-duplicate  ratio  of  two 
numbers  is  the  ratio  of  their  square 
roots.  Thus,  the  sub-duplicate  ratio  of 
the  numbers  9  and  16  is  the  ratio  of  3  to  4  ; 
that  of  the  numbers  a  and  b  is  the  ratio 
of  *Ja  to  )Jb. 

7.  Sub-medial.  A  term  synonymous 
with  transitional,  and  applied  to  the 
lower  secondary  rocks,  which  bear  a 
close  resemblance  to  some  of  the  primary 
rocks,  though  differing  from  them  in 
being  often  fragmentary,  and  in  contain- 
ing organic  remains.  They  occur  in 
England,  Scotland,  and  Wales,  where 
they  compose  the  highest  ranges,  exclu- 
sive of  the  Grampians. 

8.  Sub-multiple.  The  inverse  term  to 
multiple:  thus,  18  being  a  multiple  of  6, 
6  is  a  sub-multiple  of  18.  The  term  sub- 
multiple  is  equivalent  to  aliquot  part. 
It  is  such  a  part  of  a  quantity  as  can  be 
expressed  by  a  whole  number,  as  a  third, 
a  fourth,  &c. 

9.  Sub-normal.  In  Geometry,  the  sub- 
normal is  that  part  of  the  axis  of  a  curve 
line  which  is  intercepted  between  the 
ordinate  and  the  normal.  It  is  a  third 
proportional  to  the  sub-tangent  and  the 
ordinate. 

10.  Sub-oxide.  By  some  chemists  the 
oxides  of  the  mineral  kingdom  are 
termed  sub-oxides  and  super- oxides ;  ac- 
cording to  this  system  of  nomenclature, 
the  former  term  denotes  the  base,  the 
latter  the  acid,  and  the  quantities  of 
oxygen  are  found  in  a  simple  numerical 
proportion. 

11.  Sub-resin.  The  name  given  by 
Bonastre  to  that  portion  of  a  resin  which 
is  soluble  only  in  boiling  alcohol,  and  is 
thrown  down  again  as  the  alcohol  cools, 
forming  a  kind  of  seeming  crystal- 
lizations. It  is  a  sort  of  stearine  of 
resins. 

12.  Sub-salt.  A  salt  which  has  assumed 
a  fixed  metallic  oxide  in  the  place  of 
crystallization.  Such  compounds  may, 
therefore,  be  truly  neutral  in  compo- 
sition, the  excess  of  oxide  not  stand- 
ing in  the  relation  of  base  to  the  acid. 
The  term  'sub-salt'  originally  denoted 
a  salt  which  contained  an  excess  of  base. 

13.  Sub-stratum.  A  stratum  lying 
under  another  stratum,  as  clay  under 
gravel.  The  term  sub-soil  is  generally 
applied  to  the  matters  which  intervene 
between  the  surface  soils  and  the  rocks 
on  which  they  rest. 

14.  Sub-tangent.  In  Geometry,  the  sub- 
tangent  is  that  part  of  the  axis  of  a  curve 

320 


which  is  intercepted  between  the  tangent 
and  the  ordinate. 

15.  Sub-tense.  A  line,  angle,  &c.  which 
subtends,  or  is  opposite  to,  another  line, 
angle,  &c.  Thus,  the  cord  of  a  segment 
is  the  sub-tense  of  the  arc  which  it  cuts 
off  from  the  circle. 

SU'BERIC  ACID  {suber,  the  cork 
tree).  An  acid  procured  by  the  action  of 
nitric  acid,  with  heat,  upon  barks,  but 
more  particularly  cork.  It  forms  salts 
called  suber ates. 

SUBJECT  and  OBJECT.  These  are 
correlative  terms  employed  by  philoso- 
phical writers,  the  former  denoting  the 
mind,  soul,  or  personality  of  the  thinker 
— the  Ego,  or  self;  the  latter,  expressing 
any  thing  or  every  thing  external  to  the 
mind,  and  distinct  from  it— the  non-Ego, 
or  not-self.  The  universe  itself  when 
considered  as  a  unique  existence,  is  an 
object  to  the  thinker;  and  the  very  sub- 
ject itself  (the  mind)  can  become  an  ob- 
ject, by  being  psychologically  considered. 

Secondary  meaning.  These  terms  gra- 
dually lost  their  primary  signification. 
Object  became  metaphorically  motive, 
end,  final  cause,  &c,  by  a  common 
change  in  all  language,  of  the  meta- 
phor into  a  real  signification.  Subject 
also  became  synonymous  with  object, 
and  probably  the  logical  term  "  subject  of 
predication"  facilitate*  this  confusion. 
Be  this  as  it  may,  the  extreme  want  of 
precision  with  which  the  words  are  used, 
may  be  seen  in  the  very  common  instance 
of  calling  any  thing  "a  subject  of  in- 
vestigation."   Pen.  Cycl. 

SUBJECT  of  a  PROPOSITION.  In 
Logic,  that  term  of  a  proposition  of 
which  the  other  is  affirmed  or  denied. 
See  Predicate. 

SUBJUNCTIVE  MOOD.  The  follow- 
ing is  Mr.  Greenlaw's  rule  on  the  use 
of  this  mood : — "  If  a  clause  be  the  true 
subject  of  a  proposition,  or  be  properly 
attached  to  the  true  subject,  the  verb  of 
such  clause  is  in  the  indicative  mood; 
but  if  a  clause  be  the  true  predicate  of  a 
sentence  (provided  it  does  not  contain 
the  copula  blended  with  the  verb),  or  if 
it  be  properly  attached  to  the  true  predi- 
cate, the  verb  of  such  clause  is  invari- 
ably found  in  the  subjunctive  mood." 
See  Potential  Mood. 

SUBLIMATION.  The  process  by 
which  volatile  substances  are  raised  by 
heat,  and  again  condensed  into  the  solid 
state  ;  it  is,  in  fact,  dry  distillation.  The 
substances  so  obtained  are  called  sub- 
limates. 


sue 


SUL 


SUBLIME  GEOMETRY.  By  the 
older  mathematicians  this  term  was 
technically  applied  to  the  higher  parts 
of  geometry,  in  which  the  infinitesimal 
calculus,  or  something  equivalent,  was 
employed. 

SUBSIDIARY.  A  quantity  or  symbol 
is  so  called  when  it  is  not  essentially  a 
part  of  a  problem,  but  is  introduced  to 
help  in  the  solution.  The  term  is  par- 
ticularly applied  to  those  angles,  which 
are  introduced  into  trigonometrical  pro- 
blems, in  which  there  is  no  question  of 
angular  quantity. 

SUBSTANCE.  In  Physics,  substance 
is  synonymous  with  matter.  In  meta- 
physics, it  is  that  which  supports,  or, 
literally,  stands  under  phenomena ;  it  is 
the  fundamental  fact  of  all  existence, 
though  as  inconceivable  as  a  point  in 
mathematics. 

SUBSTITUTION,  CHEMICAL.  A 
term  explanatory  of  certain  phenomena 
connected  with  chemical  affinity.  When 
carbonate  of  soda  is  added  to  nitrate  of 
lime,  carbonate  of  lime  is  instantly  formed 
and  precipitated,  while  nitrate  of  soda  is 
formed  at  the  same  time,  and  remains  in 
solution.  Here  a  double  substitution 
occurs,  lime  being  substituted  for  soda 
in  the  carbonate,  and  soda  for  lime  in 
the  nitrate.  Such  reactions  may,  there- 
fore, be  truly  described  as  double  substi- 
tutions as  well  as  double  decompositions. 
The  substitution  of  chlorine  for  hydrogen 
in  many  organic  substances  has  been 
found  to  take  place  with  remarkable  uni- 
formity. 

SUBTRACTION.  The  arithmetical 
operation  of  removing  one  number  or 
quantity  from  another,  in  order  to  find 
their  difference.  The  operation  is  pre- 
cisely the  reverse  of  addition.  The  quan- 
tity to  be  diminished  was  formerly  called 
the  minuend ;  the  quantity  to  be  removed, 
the  subtrahend;  and  the  remaining  quan- 
tity or  difference,  the  remainder. 

SUCCINIC  ACID  (succinum,  amber). 
An  acid  derived  from  the  distillation  of 
amber,  and  found  also  in  the  resin  of  some 
coniferous  plants.  Its  compounds  with 
the  salifiable  bases  are  called  succinates. 

SUCKER.  Surculus.  A  term  applied 
in  Botany  to  a  modification  of  the  aerial 
stem,  consisting  of  a  branch  which  pro- 
ceeds from  the  neck  of  a  plant  beneath 
the  surface  of  the  ground,  and  becomes 
erect  as  soon  as  it  emerges  from  the 
earth,  producing  leaves  and  branches, 
and  subsequently  roots.  It  has  been 
termed  soboles. 
321 


SUCTION  {sugo,  to  suck).  The  act  of 
sucking;  a  term  applied  to  the  raising 
of  liquids  through  a  tube,  by  means  of  a 
piston,  which  lifts  and  sustains  the  weight 
of  the  atmosphere  from  that  part  of  the 
well  which  is  covered  with  the  tube, 
leaving  it  to  press  on  the  other  parts  of 
the  surface.     See  Pump. 

SUCTO'RIA  {sugo,  to  suck).  A  class 
of  articulate  animals,  which  have  their 
mouth  adapted  for  sucking  fluid  aliment. 
The  following  orders  are  founded  on 
differences  of  the  general  form  of  the 
body  :— 

1.  Cystica,  or  those  destitute  of  an 
anal  aperture,  which  have  one  or  more 
buccal  orifices  leading  into  a  terminal 
cyst. 

2.  Cestoidea,  or  those  with  a  long,  de- 
pressed, flat,  articulated  form,  without 
anal  aperture. 

3.  Trematoda,  or  those  with  a  short, 
broad,  depressed  body,  without  distinct 
anus,  and  with  one  or  more  orifices, 
leading  into  a  ramified  alimentary 
canal. 

4.  Acanthocephala,  or  those  with  an 
elongated  cylindrical  body,  with  the  an- 
terior part  closely  covered  with  small 
sharp  spines;  the  oral  aperture  leading 
to  a  ramified  alimentary  canal  destitute 
of  anal  opening. 

5.  Nematoidea,  or  those  with  a  long, 
cylindrical  and  often  filiform,  naked, 
inarticulated  body  traversed  by  a  straight 
alimentary  canal  open  at  both  ends,  and 
with  distinct  sexes  and  internal  impreg- 
nation. 

6.  Epizoa,  or  those  of  a  more  short 
and  entomoid  form,  with  a  sub-articu- 
lated trunk,  a  biforate  intestine,  with 
rudimentary  mandibles,  palpi,  proboscis, 
and  sometimes  antennae  and  eyes. — 
Grant. 

SUFFIX  (suffigo,  to  fasten).  A  term 
applied  by  some  mathematicians  to  the 
index  written  under  letters,  as  in  a  ,  a3f 
&c. 

SUFFRUTEX.  An  under-shrub;  a 
plant  which  differs  from  the  frutex,  or 
shrub,  in  its  perishing  annually,  either 
wholly  or  in  part ;  and  from  the  herb,  in 
having  branches  of  a  woody  texture, 
which  frequently  exist  more  than  one 
year,  as  in  the  Tree  Mignonette. 

SU'ID^S  (sus,  suis,  a  sow).  The  Pig 
tribe ;  a  group  of  pachydermatous  ani- 
mals, having  four  toes  on  each  foot,  and 
three  sorts  of  teeth  in  each  jaw. 

SULPHAMIDE.  A  compound  ex- 
actly analogous  to  oxamide,  containing 
P5 


SUL 


SUR 


the  radical  sulphurous  acid,  combined 
with  amidogen.     See  Amides. 

SULPHATES  and  SULPHITES.  The 
former  of  these  bodies  are  definite  com- 
pounds of  sulphuric,  the  latter  of  sul- 
phurous, acid  with  the  salifiable  bases. 

SULPHATOXYGEN.  According  to 
the  new  view  of  compound  radicals,  this 
body  is  the  sulphate  radical  of  sulphate 
of  soda,  the  oxygen  of  the  soda  being 
referred  to  the  acid ;  its  compounds  are 
termed  sulphatoxide. 

SULPHO-SALTS.  These  are  merely 
double  sulphurets,  in  the  constitution  of 
which  Berzelius  has  traced  a  close  ana- 
logy to  salts.  The  sulphurets  of  the 
most  electro-positive  metals  have  been 
termed  sulphur  bases,  whilst  the  sulphu- 
rets of  arsenic,  antimony,  &c.  have  been 
called  sulphur  acids :  the  combination  of 
these  bases  and  acids  are  sulphur  salts. 

SULPHOVINIC  ACID.  (Enothionic 
acid.  An  acid  formed  by  the  action  of 
sulphuric  acid  upon  alcohol. 

SULPHUR.  Brimstone.  An  elemen- 
tary substance  exhaled  in  large  quan- 
tities from  volcanoes,  either  in  a  pure 
state  or  in  combination  with  hydrogen  ; 
by  condensing  in  fissures  it  forms  sul- 
phur veins,  from  which  the  greater  part 
of  the  sulphur  of  commerce  is  derived. 
It  exists  also  in  combination  with  metals, 
and  is  extracted  in  considerable  quantity 
from  bisulphuret  of  iron  or  iron  pyrites. 
It  is  likewise  a  constituent  of  sulphuric 
acid  in  gypsum  and  other  native  sul- 
phates. Lastly,  it  enters  into  organic 
structures,  being  associated  with  albu- 
men, in  the  fluid  or  the  solid  state. 

Crude  Sulphur  is  the  result  of  the  dis- 
tillation of  native  sulphur  ;  roll  or  stick 
sulphur  is  sulphur  which  has  been  refined 
and  cast  into  wooden  moulds ;  flowers  of 
sulphur  is  the  name  given  to  sulphur 
which  has  been  sublimed,  in  the  form 
of  a  bright  yellow  powder. 

SULPHURET.  A  combination  of  sul- 
phur with  a  base.  A  sulphuret  is  some- 
times distinguished  by  the  colour  of  the 
compound,  as  the  black  and  the  red  sul- 
phuret of  mercury. 

SULPHURIC  ACID.  An  acid  pro- 
duced by  the  burning  of  sulphur,  mixed 
with  nitrate  of  potash.  It  was  formerly 
called  oil  of  vitriol,  because  it  was  dis- 
tilled from  a  substance  of  mineral  origin, 
called  vitriol  on  account  of  its  imperfect 
resemblance  to  green  glass.  This  acid, 
when  obtained  in  the  latter  way,  emits 
white  vapours  on  exposure  to  the  air, 
and  is  hence  caMe&fuming  sulphuric  acid.  , 
322 


SULPHUROUS  ACID.  A  gas  ob- 
tained by  burning  sulphur  in  dry  air  or 
in  oxygen  gas.  By  means  of  nitric  acid, 
the  sulphurous  is  immediately  converted 
into  sulphuric  acid. 

SUN.  The  centre  of  the  solar  system, 
and  the  dispenser  of  light  and  heat  to 
all  the  planets.  Its  distance  from  the 
earth  is  computed  at  95  millions  of  miles, 
its  diameter  at  882,000  miles,  and  its 
bulk  is  about  thirteen  hundred  thousand 
times  greater  than  that  of  the  earth. 

SUN-STONE.  A  yellow  variety  of 
adularia,  or  naker  felspar,  with  reddish 
dots.  This  name  is  also  sometimes  given 
to  the  beautiful  avanturino  variety  of 
common  felspar. 

SUPERDOMINANT.  The  sixth  of 
the  key,  in  the  descending  scale  of  Music. 
The  supertonic  is  the  second  above  the 
key-note. 

SUPERFICIES.  Popularly,  the  sur- 
face of  any  thing.  In  Geometry,  it  de- 
notes the  boundary  of  a  solid,  and  relates 
to  the  two  dimensions  of  length  and 
breadth.  The  quantity  of  an  area  is 
called  its  superficial  content,  as  distin- 
guished from  linear  content  or  length, 
and  from  solid  content  or  bulk.  See 
Surface. 

SUPERPOSITION.  The  process,  in 
Geometry,  by  which  one  magnitude  may 
be  conceived  to  be  placed  upon  another, 
so  as  exactly  to  cover  it,  or  so  that  every 
part  of  each  shall  exactly  coincide  with 
every  part  of  the  other.  It  is  evident 
that  any  magnitudes  which  admit  of 
superposition  must  be  equal,  or,  rather, 
this  may  be  considered  as  the  definition 
of  equality. 

SU'PER-SALT.  A  compound  of  an 
acid  and  a  base,  in  which  the  acid  is  in 
excess.    See  Sub-salt. 

SUPPLEMENT.  In  Trigonometry, 
the  supplement  of  an  arc  is  its  defect 
from  a  semicircle  ;  the  supplement  of  an 
angle,  its  defect  from  two  right  angles, 
or  180°.  Also,  chords  or  arcs  of  a  circle 
or  other  curve  which  have  a  common  ex- 
tremity, and  together  subtend  an  angle 
of  two  right  angles  at  the  centre,  are 
sometimes  called  supplemental  chords  or 
arcs.  The  supplemental  versed  sine,  or 
suversed  sine  is  the  difference  between 
the  versed  sine  and  the  diameter. 

SUPRACRETACEOUS  ROCKS.  A 
term  applied  by  geologists  to  certain 
rocks  or  strata  which  are  situated  above 
the  chalk.  They  are  also  termed  ter- 
tiary strata. 
SURD.    This  term  denotes,  in  Alge- 


SUR 


sus 


bra,  an  irrational  or  incommensurable 
quantity,  or  a  quantity  of  which  the  root 
cannot  be  exactly  determined.  It  is  not, 
in  fact,  a  complete  power,  and  it  must 
therefore  be  expressed  either  by  the  radi- 
cal sign,  or  by  its  fractional  index.  Thus 
the  square  root  of  2  must  be  expressed 

either  by  *J2,  or  by  2^ ;  the  cube  root 

of  3,  by  a/3,  or  by  3* ;  the  n  the  root 


of  a  +  b,  by  ?J  a  +  b,  or  by  {a  +  b) %  • 
The  etymology  of  the  term  surd  is  un- 
known. 

SURFACE.  Superficies.  In  Geometry, 
ti  plane  surface  is  such  that  the  right 
line,  which  joins  every  two  points  which 
can  be  assumed  upon  it,  lies  entirely  in 
the  surface.  By  Plato  it  was  defined  to 
be  a  surface  whose  extremities  hide  all 
the  intermediate  parts,  the  eye  being 
placed  in  its  continuation.  It  has  been 
also  defined  as  "  the  smallest  surface 
which  can  be  contained  between  given 
extremities."  Every  surface  which  is 
not  a  plane,  or  composed  of  planes,  is 
called  a  curved  surface.  All  plane  sur- 
faces are  perfectly  alike  in  their  proper- 
ties, but  curved  surfaces  admit  of  endless 
variety. 

1.  Surf  aces  of  the  first  order  are  those 
in  which  the  equation  is  of  the  first  de- 
gree, containing  only  plane  surfaces. 
Surfaces  of  the  second  order  are  those  in 
which  the  equation  is  of  the  second  de- 
gree ;  these  surfaces  hold  the  same  place 
among  surfaces  as  is  held  by  curves  of 
the  second  degree,  or  conic  sections, 
among  curves ;  and  every  section  made 
by  a  plane  with  any  surface  of  the  second 
degree  must  be  a  curve  of  the  second 
degree.  The  surfaces  of  the  second  de- 
gree are  the  ellipsoid,  the  single  and  the 
double  hyperboloid,  the  elliptic  parabo- 
loid, and  the  hyperbolic  paraboloid. 

2.  Cylindrical  surfaces  are  those  gene- 
rated by  a  straight  line  infinitely  pro- 
duced in  both  directions,  which  moves 
so  as  always  to  be  parallel  to  a  given  line, 
and  to  have  one  of  its  points  on  a  given 
curve. 

3.  Conical  surfaces  are  generated  by  a 
straight  line  infinitely  produced  in  both 
directions,  which  always  passes  through 
a  given  point  or  vertex,  and  has  one 
point  in  a  given  curve.  The  common 
cylinder  and  the  cone  would  be  described 
in  this  science  as  a  right  circular  cylinder 
and  a  right  circular  cone.  The  cylin- 
drical surfaces  themselves  are  only  an 
extreme  case  of  the   conical    surfaces, 

323 


being  what  the  latter  become  when  the 
vertex  is  removed  to  an  infinite  dis- 
tance. 

4.  Surfaces  of  revolution  are  generated 
by  the  rotation  of  a  curve  about  an  axis, 
relatively  to  which  it  always  retains  one 
position.  The  common  cone  and  cylin- 
der, the  sphere,  and  others  of  the  greatest 
practical  use,  are  contained  in  this 
class. 

5.  Tubular  surfaces  are  generated  by  a 
circle  of  given  radius,  which  moves  with 
its  centre  on  a  given  curve,  and  its  plane 
at  right  angles  to  the  tangent  of  that 
curve.  When  the  given  curve  is  a  circle, 
the  tubular  surface  is  a  common  ring. 

6.  Ruled  surfaces  (the  ■  surfaces  re- 
glees'  of  the  French  writers)  are  those 
which  are  described  by  the  motion  of  a 
straight  line,  which  neither  remains 
parallel  to  a  given  line,  nor  always  passes 
through  a  given  point.  This  includes, 
among  many  others,  the  whole  class  of 
conoidal  surfaces,  made  by  a  straight 
line  which  moves  parallel  to  a  given 
plane,  and  always  passes  through  a 
straight  line  perpendicular  to  that  plane 
and  a  given  curve.  The  surface  of  a 
spiral  staircase,  as  it  would  be  if  there 
were  no  steps,  but  only  a  gradual  ascent, 
is  an  instance. 

7.  Developable  surfaces  are  those  which 
can  be  unwrapped  on  a  plane  without 
any  doubling  of  parts  over  one  another, 
or  separation ;  that  is,  without  being 
rumpled  or  torn.  The  only  familiar  in- 
stances are  the  cylinder  and  the  cone. — 
Pen.  Cycl. 

8.  Surface  gauche.  The  name  given  by 
the  French  geometers  to  a  surface  which 
cannot  be  developed  on  a  plane,  the 
generating  straight  line  being  constrained 
to  move  so  that  no  two  of  its  consecutive 
positions  are  in  the  same  plane. 

SURSOLID.  In  Arithmetic,  the  fifth 
power  of  a  number.  Thus  32  is  the  sur- 
solid  of  2. 

SU'RTURBRAND.  The  name  given 
in  Iceland  to  brown  coal  or  bituminous 
wood  ;  a  variety  of  coal  which  retains  the 
structure  of  wood  unchanged,  and  re- 
sembles peat  in  the  phenomena  produced 
during  combustion.  This  is  called  in 
Devonshire  Bovey  coal. 

SUSPENSION.  A  term  applied  to 
the  state  of  solid  bodies,  the  particles  of 
which  are  held  undissolved  in  water,  and 
may  be  separated  from  it  by  filtration. 
The  solid  is  then  said  to  be  suspended  in 
the  liquid. 

SUSSEX  MARBLE.  A  variety  of 
P6 


S  YC 


SYM 


limestone  constituting  one  of  the  fresh- 
water deposits  of  the  Wealden  group,  and 
occurring  in  layers  varying  from  a  few 
inches  to  upwards  of  a  foot  in  thickness, 
the  layers  being  separated  by  seams  of 
clay  or  of  friable  limestone. 

SUTURE  {sutura,  a  seam).  1.  A  term 
applied,  in  Botany,  to  the  junction  of  the 
valves  of  a  simple  carpel,  as  of  the  le- 
gume. The  junction  corresponding  to 
the  margins  of  the  carpellary  leaf,  is 
called  the  ventral  suture ;  that  which 
corresponds  to  the  midrib  of  the  carpel- 
lary leaf,  is  the  dorsal  suture.  2.  In 
Malacology,  the  term  suture  is  applied  to 
the  line  of  junction  in  the  whorls  of 
spiral  shells,  or  to  that  line  by  which  two 
parts  join  or  fit  into  each  other.  3.  In 
Entomology,  it  is  the  line  at  which  the 
elytra  meet  and  are  sometimes  confluent. 

SYCHNOCA'RPOUS  (<ruXv6s,  fre- 
quent, napTrbs,  fruit).  Polycarpous.  A 
term  used  in  Botany  to  signify  the  dura- 
tion of  vegetable  existence,  and  denoting 
the  power  of  bearing  fruit  many  times 
without  perishing.  Those  plants  whose 
stem  endures  many  years,  constantly 
bearing  flowers  and  fruits,  as  trees  and 
shrubs,  are  designated  as  caulocarpous ; 
while  those  whose  root  endures  many 
years,  but  whose  stems  perish  annually, 
as  herbaceous  plants,  are  called  rhizo- 
carpous. 

SY'CONUS  (avKov,  a  fig).  The  Bota- 
nical name  of  an  aggregate  fruit,  con- 
sisting of  a  fleshy  rachis,  having  the 
form  of  a  flattened  disk,  or  of  a  hollow 
receptacle,  with  distinct  flowers  and  dry 
pericarps,  as  in  the  fig,  the  dorstenia,  &c. 


SY'ENITE.  A  variety  of  granite  con- 
taining hornblende  instead  of  mica,  and 
so  called  from  its  being  brought  from 
Syene  in  Egypt. 

SY'LLOGISM  ((rvWofia/jLoi.  a  reckon- 
ing all  together ;  reasoning).    A  demon- 
strative argument,  in  which  a  conclusion 
is  deduced  by  comparison   of  its  terms 
with  a  middle  term.     It  is  a  strictly  logi- 
cal form  of  argument,  the  conclusiveness 
of  which  is  manifest  from  the  structure 
of  the  expression  alone,  without  any  re- 
gard   to    the    meaning    of    the    terms. 
Thus- 
All  tyrants  deserve  death  ; 
Caesar  was  a  tyrant ; 
Therefore  he  deserved  death. 

SY'LVANITE.  Native  tellurium, 
found  in  some  of  the  Transylvanian  ores. 

SY'LVIADjE  {sylvia,  the  warbler). 
The  Warblers ;  a  family  of  the  Inses- 
sores,  or  perching  birds,  or  the  Canta- 
trices  of  Macgillivray,  characterized  by 
their  small  size,  none  of  them  much  ex- 
ceeding the  nightingale.  Most  of  them 
are  migratory.     See  Dentirostres. 

SYMBOLS,  CHEMICAL.  An  abbre- 
viated mode  of  expressing  the  composi- 
tion of  bodies.  The  elementary  sub- 
stances, instead  of  being  written  at  full 
length,  are  indicated  by  the  first  letter  of 
their  names,  a  second  letter  being  em- 
ployed when  more  than  one  substance 
begins  with  the  same  letter,  — thus  C 
stands  for  carbon,  Al  for  aluminium,  As 
for  arsenic,  &c.  These  symbolic  expres- 
sions, or  chemical  formuV,ce,  are  given  in 
the  subjoined  table. 


TABLE  OF  SYMBOLS 


Elements. 

Sym. 

Elements. 

Sym. 

Elements. 

Sym. 

Aluminium      .     .     . 

Al 

Gold  (Aurum) .    .    . 

Au 

Potassium  (Kalium) 

K 

Antimony  (Stibium) 

Sb 

Hydrogen    .    .    .    . 

H 

Rhodium     .     .     .    . 

R 

Arsenic 

As 

Iodine 

1 

Selenium     .    .     .    . 

Se 

Barium 

Ba 

Iridium 

Ir 

Silicium 

Si 

Bismuth      .    .    .    . 

Bi 

Iron  (Ferrum) .    .    . 

Fe 

Silver  (Argentum) 

Ag 

Boron 

B 

Lead  (Plumbum) 

Pb 

Sodium  (Natrium) 

JSa 

Bromine      .    .    .    . 

Br 

Lithium 

L 

Strontium    .    .    .    . 

Sr 

Cadmium     .    .    .    . 

Cd 

Magnesium      .    .    . 

Mg 

Sulphur 

S 

Calcium 

Ca 

Manganese  .... 

Mn 

Tellurium    .    .    .    . 

Te 

Carbon 

C 

Mercury  (Hydrargy- 

Thorium     .    .    .    . 

Th 

Cerium 

Ce 

rum)    

Hg 

Tin  (Stannum)     .    . 

Sn 

Chlorine 

CI 

Molybdenum   .    .    . 

Mo 

Titanium     .    .    .    . 

Ti 

Chromium  .    .    .    . 

Cr 

Nickel 

Ni 

Tungsten       (Wol- 

Cobalt  

Co 

Nitrogen      .... 

N 

fram)    

W 

Columbium     Tanta- 

Osmium     .... 

Os 

Vanadium    .    .    .    . 

V 

lum      

Ta 

Oxygen 

O 

Uranium     .    .    .    . 

u 

Copper  (Cuprum) 

Cu 

Palladium    .    .    .    . 

Pd 

Yttrium       .    .    .    . 

Y 

Fluorine 

F 

Phosphorus      .    .    . 

P 

Zinc 

Zn 

Glucinium  .    .    .    . 

G 

Platinum     .    .    .    . 

PI 

Zirconium  .    .    .    . 

Zx 

SYM 


S  YM 


1.  Each  symbol  represents  one  equiva- 
lent of  the  elementary  substance  :  thus  H 
denotes  one  equivalent  of  hydrogen.  A 
figure  prefixed  multiplies  the  symbol: 
thus  2H,  3H,  4H,  denote  two,  three, 
and  four  equivalents,  respectively.  Two 
equivalents  are  sometimes  denoted  by 
placing  a  dash  through,  or  under,  the 
symbol :  thus  H ,  or  H,  signifies  the 
same  as  2  H,  or  two  equivalents. 

2.  Compounds  are  represented  by 
placing  the  symbols  of  their  elements 
together.  Thus,  S  F  e  denotes  sulphuret 
of  iron.  Or  the  compound  may  be 
expressed  by  an  algebraic  formula,  as 
S+Fe. 

3.  A  dot  ( • )  prefixed  to,  or  placed  over, 
a  symbol,  indicates  one  equivalent  of 
oxygen.  Thus  -H  or  H  denotes  one  equi- 
valent of  oxygen  and  one  of  hydrogen, 
or  H  +  O.  Each  additional  dot  denotes 
another  equivalent :  thus,  :C,  or  C,  de- 
notes one  equivalent  of  carbon  and  two 

of  oxygen,  or  carbonic  acid  ;  :  •  N,  or  N, 
denotes  one  of  nitrogen  and  five  of  ox- 
ygen, or  nitric  acid. 

4.  A  figure  prefixed  to  any  symbols 
multiplies  all  the  following  symbols 
which  are  not  separated  from  it  by  a  + 
sign.  Thus  2  •  H  -S  =  2  •  H  +  2  j  S; 
in  this  case,  the  compounds  *H  and  •  S 
are  both  multiplied  by  2.  But  in  the  fol- 
lowing formula, 

2  H  •  S  +  K  =  2  H  +  2  I S  +   K, 
the  two  first  compounds  only  are  multi- 
plied by  2,  the  third  being  merely  added. 

5.  A  figure  placed  after  any  symbol 
multiplies  that  symbol,  but  does  not  effect 
any  other  symbol  in  the  formula.  Thus, 
H2  C  =  2  H  +  C ;  in  this  case,  H  is  mul- 
tiplied, while  C  is  only  added.  In  the 
formula,  N  H3  =  N  +  3  H,  the  latter 
symbol  alone  is  multiplied. 

6.  In  complicated  combinations,  brackets 
are  often  used  to  contain  the  symbols 
which  are  supposed  to  be  united.  Thus, 
in  the  formula 

[2HC2N  +  C2NFe]  +  2   K, 
there  are  two  compounds ;  the  former  is 
composed  of  the    symbols    within    the 
brackets,  the  latter  consists  of  the  sym- 
bols placed  outside  the  brackets. 

7.  A  figure  prefixed  to  any  number  of 
symbols  enclosed  within  brackets,  multi- 
plies them  all,  whether  there  are  inter- 
vening signs  or  not.  A  figure  prefixed 
to  the  symbols  within  the  brackets  in  the 
preceding  paragraph,  multiplies  them  all, 
but  does  not  effect  the  symbol  outside 
the  brackets. 
325 


8.  The  animal  and  vegetable  acids 
were  expressed  by  Berzelius  by  the  first 
letter  of  their  names,  with  a  dash  over 
it :  thus  T,  A,  C,  are  the  symbols  for  tar- 
taric, acetic,  and  citric  acids.  By  others, 
they  are  represented  by  Italic  capitals, 
some  succeeding  letter  being  added  when 
more  than  one  acid  have  the  same  initial 
letter :  thus  Ty  A,  Ct,  represent  the  acids 
above  mentioned. 

9.  A  few  exercises  on  symbols  are  here 
added.  To  the  left  of  the  sign  (  =  )  are 
placed  the  materials  used  ;  to  the  right, 
the  products  formed  by  their  reaction. 
The  symbol  '  & '  is  used  to  signify  a  sub- 
stance added  to,  or  separated  from,  an- 
other, while  +  is  placed  between  sub- 
stances chemically  combined : 

Materials.  Products. 

H&Fe    m       Fe&H 
H&Fe&  ;S    =     IS  -Fe&H 


:Hg    =    Hg&02 
2  :Mn  =    :Mn2&0 


5  -N2&P2  =  ;;P2&10N 
4-N2&  SFe  =  :S  -Fe&8N 


:jN     =       jN&O 
2::N&:N  =  3  •  jN 


S  &  02  =  :  S 
HS  &  08  =  ■  H  &  :  S 


A  Pb&  Z  =  A  Z&Pb 
:C-Pb&HS  =  -H&SPb&  :C 
SY'MMETRY  (avunerpos,  commen- 
surable). The  etymological  meaning  of 
this  term,  and  the  meaning  with  which 
it  was  first  employed,  in  mathematics,  by 
Euclid,  is  commensur ability :  two  mag- 
nitudes, then,  were  symmetrical  which 
admitted  of  a  common  measure ;  hence, 
the  term  was  applied  to  magnitudes 
which  coincide. 

1.  But  Coincidence  had  been  already 
denoted  by  the  terms  equal  and  similar, 
the  former  relating  to  size,  the  latter  to 
form.  Symmetry,  therefore,  was  even- 
tually employed  to  express  that  obvious 
relation  of  equal  and  similar  figures, 
which  refers  to  ihe\r position  merely,  and 
consists  in  their  corresponding  portions 
being  similarly  placed  on  different  sides 
of  the  same  straight  line.  In  the  letter 
W  there  is  a  want  of  symmetry,  but  not 
in  O  :  to  make  W  symmetrical,  both  the 
inner  lines  should  be  thin,  and  both  the 
outer  lines  thick. 

2.  In  Algebra,  a  function  is  said  to  be 
symmetrical  with  respect  to  any  two 
letters,  when  it  would  undergo  no  change 


S  YN 


S  YN 


if  these  letters  were  interchanged,  or  if 
each  were  made  to  take  the  place  of  the 
other. 

3.  In  Mathematical  language,  the  term 
symmetry  denotes  that  quantities  which 
in  any  manner  have  a  common  relation, 
should  have  something  common  in  the 
symbols  of  notation  ;  and  analogy  is, 
perhaps,  a  better  word  than  symmetry. — 
Pen.  Cycl. 

SYMPATHETIC  INK.  A  solution  of 
chloride  of  cobalt.  The  characters  made 
on  paper  with  this  preparation,  when  dry, 
will  be  invisible;  on  being  held  to  the 
fire,  the  writing  will  assume  a  bright 
blue  or  green  colour  ;  as  the  paper  cools, 
the  colour  will  again  disappear,  in  con- 
sequence of  its  absorbing  moisture  from 
the  air;  and  the  phenomenon  may  be  re- 
produced many  times  in  succession. 

SYMPATHETIC  SOUNDS.  A  term 
expressive  of  that  natural  relation  of 
sounds  which  occurs  in  harmonical  com- 
binations, and  is  particularly  illustrated 
by  the  sounds  of  the  jEolian  harp.  The 
term  is  also  applied  to  sounds  produced 
in  one  instrument  by  sounding  another 
close  to  it;  but  these  are  dependent,  not 
on  sympathy,  but  on  the  vibrations  of  the 
intervening  air. 

SYMPIESO'METER  {avu-niefa,  to 
compress,  juerpov,  a  measure).  An  in- 
strument for  measuring  the  weight  of 
the  atmosphere  by  the  compression  of  a 
column  of  gas. 

SYN-  {avv).  A  Greek  preposition,  sig- 
nifying with,  together.  For  the  sake  of 
euphony,  the  final  n  of  the  preposition  is 
changed  into  m  before  the  labials  b,  m, 
p>  ph,  ps,  &c,  as  in  symmetry,  sym- 
pathy, &c. ;  into  s,  I,  r,  before  these 
letters,  as  in  syllable,  &c. ;  and  is  entirely 
omitted  when  followed  by  two  conso- 
nants, or  a  double  one,  as  in  syzygy. 

SYNCA'RPIUM  {avv,  together,  Kap- 
iros,  fruit).  The  botanical  designation 
of  an  aggregate  fruit,  in  which  the  ova- 
ries cohere  into  a  solid  mass,  with  a 
slender  receptacle,  as  in  magnolia,  anona, 
&c. 

SYNCA'RPOUS  {avv,  together,  Kapnos , 
fruit).  A  term  applied,  in  Botany,  to 
those  fruits  in  which  the  carpels  cohere 
together,  as  in  poppy ;  when  the  carpels 
are  distinct  from  one  another,  the  fruit  is 
termed  apocarpous,  as  in  ranunculus. 

SYNCATEGOREMA'TIC  {avyKarn- 
t6pr\p.a,  that  which  is  said,  or  can  be 
said,  of  a  person  or  thing  along  with 
other  words).  In  Logic,  syncategore- 
matic  words  are  such  as  cannot  singly 
326 


express  a  term,  but  only  a  part  of  a 
term;  these  are  adverbs,  prepositions, 
&c,  and  also  nouns  in  any  other  case 
besides  the  nominative. 

SYNCHRONOUS  {avv,  together,  Xp<5- 
vov,  time).  That  which  occurs  in  equal 
times,  as  the  strokes  of  the  pulse  ;  a  term 
synonymous  with  isochronous. 

SYNDA'CTYLES  {avv,  together,  ddn- 
tv\os,  a  toe).  A  group  of  birds  which 
have  the  external  toe  nearly  as  long  as 
the  middle  one,  and  united  to  it  as  far  as 
the  second  joint.  The  group  contains 
the  bee-eaters,  the  king-fishers,  the  horn- 
bills,  the  motmots,  and  the  todies. 

SYNGENE'SIOUS  {avv,  together,  ye- 
veats,  growth).  A  term  applied  to  the 
anthers  of  plants  which  grow  together 
by  their  margins,  as  in  the  Compositae. 
A  more  precise  term  is  syn-antherous. 

SYNGNA'THIANS  {avv,  together, 
yvdOos,  a  jaw).  A  family  of  lophobran- 
chiate  fishes,  in  which  the  lengthened 
jaws  are  united  by  a  surrounding  integu- 
ment, forming  a  tubular  mouth ;  they  are 
named  from  the  genus  syngnathus,  or  the 
pipe-fish.  The  name  is  also  applied  to  an 
order  of  myriapodous  insects,  comprising 
the  Scolopendridae  and  the  Geophilidse. 

SYNODICAL  PERIOD  {avvoboi,  a 
conjunction  of  paths).  The  simplest  in- 
stance of  a  synodical  period  is  afforded 
by  the  two  hands  of  a  watch  :  the  minute 
hand  revolves  in  one  hour,  the  hour  hand 
in  twelve  hours ;  but  the  synodic  revo- 
lution of  the  two  hands  is  the  interval 
which  elapses  between  any  time  at  which 
they  are  together,  and  the  next  time  at 
which  the  same  thing  takes  place.  "  This 
term  is  applied  in  astronomy  to  the 
lunar  month,  or  the  period  of  a  revolu- 
tion of  the  moon  round  the  earth  from 
one  synod,  or  conjunction  with  the  sun,  to 
another ;  thus,  taking  the  sun's  actual 
revolution  at  365|  days,  and  the  moon's 
at  27\  days,  we  have 

SYNTAX  {avv,  together,  rdfo,  ar- 
rangement). That  part  of  grammar, 
which  shows  how  individual  words,  the 
materials  of  language  (the  department  of 
etymology),  are  to  be  arranged  together, 
so  as  to  form  sentences,  or  affirmations 
containing  sense. 

SYNTHESIS  {avvOeau,  a  putting  to- 
gether). This  term  denotes  composition, 
and  expresses  a  process  the  very  reverse 
of  analysis,  or  resolution.  The  term 
Analysis  is  given  to  a  species  of  mathe- 
matical investigation,  which  commencing 


TAB 


T  AC 


with  the  assumption  of  that  which  is 
sought  as  if  it  were  given,  a  chain  of  rela- 
tions is  pursued  which  terminates  in 
what  is  given  (or  may  be  obtained)  as  if 
it  were  sought.  The  term  Synthesis  de- 
notes a  process  in  which  the  series  of 
relations  exhibited  commences  with  what 
is  given,  and  ends  with  what  is  sought. 
Consequently  analysis  is  the  instru- 
ment of  invention,  and  synthesis  that  of 
instruction.     See  Analysis. 

Synthesis,  chemical.  The  formation  of 
any  body  by  combination  of  its  elements, 
as  opposed  to  analysis,  or  the  resolution 
of  a  body  into  its  component  parts.  In 
the  analytic  operation,  a  portion  of  water 
is  separated,  by  means  of  galvanism,  into 
the  two  elementary  gaseous  bodies, 
oxygen  and  hydrogen;  in  the  synthetic 
operation,  these  two  gases  are  again 
made  to  combine,  by  means  of  the  elec- 
tric spark,  and  a  portion  of  water  is 
again  produced. 

SYRINGE  (<tvPi^,  a  pipe  or  tube). 
The  common  squirt,  or  hand-syringe,  con- 
sists of  a  cylinder  or  barrel,  furnished 
with  an  accurate  piston ;  at  the  end  of 
the  barrel  is  a  short  suction-pipe ;  there 
is  no  valve.     The  action  of  the  atmo- 


spheric pressure  is  the  same  as  in  the 
suction-pump  (see  Pump).  The  water 
which  is  raised  into  the  barrel  is  driven 
thence  into  the  suction-pipe,  and  pro- 
jected into  the  air  by  mechanical  force. 
The  act  of  respiration,  of  suction  by  the 
mouth,  of  drinking,  of  smoking,  &c, 
may  all  be  explained  by  reference  to  the 
same  principle. 

SY'RPHIDiE.  A  family  of  dipterous 
'insects,  belonging  to  the  section  Atheri- 
cera,  named  from  the  genus  syrphus,  and 
closely  resembling  the  wasps  and  hum- 
ming-bees. 

SYSTEM  (owrrijiia,  a  whole  com- 
pounded of  several  parts).  A  harmoni- 
ous arrangement  of  bodies  with  respect 
to  one  another,  and  of  the  laws  by  which 
their  motions,  functions,  or  develop- 
ments are  supposed  to  be  regulated.  See 
Hypothesis. 

SYZYGY  (av&yia,  union).  The  name 
given  in  common  to  the  moon's  oppo- 
sition to,  and  her  conjunction  with,  the 
sun.  The  quadratures  are  the  positions 
precisely  intermediate  between  the  syzy- 
gies  ;  at  new  and  full  moon  the  moon  is 
in  her  syzygies  ;  at  half  moon,  in  her  qua- 
dratures.    See  Phases  and  Quadrature. 


TABA'NIDjE.  The  Gad-fly  tribe;  a 
family  of  dipterous  insects,  belonging  to 
the  section  of  Tanystoma,  and  distin- 
guished by  their  powers  of  perforating 
the  skin  and  sucking  the  blood  of  vari- 
ous quadrupeds,  and  even  of  man. 

TABASHEER.  A  siliceous  substance 
found  in  the  joints  of  the  bamboo,  some- 
times fluid,  but  generally  in  a  concreted 
state.  In  foreign  countries  it  is  termed 
bamboo  milk,  salt  of  bamboo,  and  bamboo 
camphor.  The  word  is  derived  from  the 
Persian  scher,  or  the  Sanscrit  kschirum, 
signifying  milk. 

TABLE-LAND.  An  elevated  plain 
rising  abruptly  from  the  general  level  of 
the  country,  and  being,  as  it  were,  the 
broad  and  horizontal,  or  gently  undulat- 
ing top  bf  an  immense  mountain,  as  the 
Nilgherry  district  of  India.  Sometimes 
there  are  several  such  plains  placed  one 
upon  another,  at  least  on  one  or  two 
sides,  when  they  are  called  platforms  or 
terraces,  as  those  on  the  eastern  slope  of 
the  Cordillera  of  New  Mexico. 

TABLE-LAYERS.    This  term  is  ap- 
plied by  geologists  to  extended  plates  of 
327 


rock,  not  divided  into  parallel  laminae. 
Dr.  MacCullock  proposes  to  call  them 
pseudo-strata.  Mr.  Bakewell  remarks  on 
what  he  calls  the  stratiform  structure, 
that  many  masses  of  rock,  not  really 
stratified,  occur  divided  into  parallel 
planes,  by  seams  or  divisions  which  re- 
semble those  found  in  regular  strata; 
such  planes  have  not  been  super-imposed 
in  succession,  but  are  the  result  of  a 
crystalline  arrangement  of  the  mass. 

TABULAR  SPAR.  Table  Spar.  An- 
other name  for  prismatic  augite,  a  mine- 
ral occurring  in  primitive  rocks,  asso- 
ciated with  brown  garnets. 

TABULAR  STRUCTURE.  A  term 
expressing  the  geological  character  of  a 
rock  which  is  composed  of  paralled  plates 
or  tables,  separated  by  regular  seams. 

TACHO'METER  (rdxos,  velocity,  Me- 
rpov,  a  measure).  An  instrument  in- 
vented for  the  purpose  of  indicating 
minute  variations  in  the  velocity  of 
machines. 

TACHYDRO'MIANS  (tclXvs,  rapid, 
dponos,  a  course).  A  term  applied  to  a 
family  of  wading  birds,  of  which  the 


T  AL 


TAN 


genus  tachydromus  is  the  type  ;  also  to  a 
family  of  saurian  reptiles,  and  to  a  family 
of  dipterous  insects. 

TA'CHYLITE.  A  mineral  which  re- 
sembles obsidian,  and  has  also  been  sup- 
posed to  be  similar  to  isopyre.  It  occurs 
in  small  masses  in  basalt  and  wacke. 

TACKING.  A  nautical  term  for  an 
operation  with  the  rudder  and  sails,  by 
which,  when  a  ship  is  proceeding  in  the 
course  of  an  acute  angle  with  the  direc- 
tion of  the  wind  on  one  of  her  bows,  her 
head  may  be  turned  towards  the  wind,  so 
as  to  enable  her  to  sail  on  a  course 
making  nearly  the  same  angle  with  its 
direction  on  the  other  bow. 

TA'GLIA.  A  name,  borrowed  from 
the  Italian,  for  a  particular  combination 
of  pulleys.  The  term  is  applied  either 
to  a  system  of  fixed  pulleys  collected  in 
one  common  block ;  or  to  a  system  of 
moveable  pulleys  in  a  separate  block,  to 
which  the  weight  is  attached.  Several 
taglias  may  be  so  combined  that  one  acts 
upon  another;  this  arrangement  con- 
stitutes a  compound  taglia. 

TALC.  A  simple  mineral,  laminated 
like  mica,  and  often  similar  in  colour. 
It  is  easily  distinguished  from  this  mine- 
ral by  being  much  softer,  and,  although 
flexible,  not  elastic.  It  occurs  as  a  con- 
stituent of  certain  rocks. 

TALC-SLATE.  A  talcose  rock,  con- 
sisting of  talc  and  quartz  arranged  in 
laminae ;  it  is  of  various  colours,  glisten- 
ing, and  has  an  unctuous  feel.  It  is 
generally  associated  with  steatite,  asbes- 
tus,  actinolite,  and  serpentine. 

TALCITE.  A  rare  mineral,  called 
nacrite  by  Jameson,  and  earthy  talc  by 
Werner.  It  occurs  in  veins,  with  sparry 
limestone  and  galena,  in  the  mining  dis- 
trict of  Freyberg. 

TALCOSE  GRANITE.  Protogene. 
A  mixture  of  felspar,  quartz,  and  talc  or 
chlorite.  It  occurs  in  Cornwall,  where, 
on  decomposing,  it  yields  the  China-clay 
or  Porcelain-earth,  which  is  annually  ex- 
ported in  large  quantities. 

TALCOSE  ROCKS.  These  resemble 
the  micaceous  rocks,  and  comprise  chlo- 
rite-slate,  talc-slate,  and  serpentine. 

TA'LPIDjE  {talpa,  a  mole).  The 
Mole  tribe ;  a  family  of  the  insectivorous 
vertebrata,  characterized  by  their  subter- 
ranean habits. 

TALUS.  A  term  applied  to  a  sloping 
heap,  formed  of  fragments  broken  off  by 
the  action  of  the  weather  from  the  face 
of  a  steep  rock,  and  accumulated  at  its 
base.  The  word  talus  is  borrowed  from 
328 


the  language  of  fortification,  in  which  It 
denotes  the  outside  of  a  wall  of  which 
the  thickness  is  diminished  by  degrees, 
as  it  rises  in  height,  to  make  it  the 
firmer. 

TANGENT  {tango,  to  touch).  A 
straight  line  which  touches,  but  does  not 
cut,  a  curve.  A  straight  line  is  said  to 
be  a  tangent  to  a  circle,  when  it  touches 
the  circumference  only  on  one  point, 
'  making  a  right  angle  with  the  radius  at 
the  point  of  contact.  In  Mechanics,  a 
force,  which  acts  upon  a  wheel  in  the 
direction  of  such  a  line,  is  said  to  be  tan- 
gential ;  and  it  is  in  this  direction  that 
motion  is  communicated  between  wheels 
and  pinions,  or  from  one  wheel  to  an- 
other. 

1.  Tangent  of  an  angle  or  arc.  Aline 
drawn  from  that  extremity  of  the  arc 
through  which  the  diameter  of  the 
circle  passes  (which  extremity  is  called 
the  beginning  of  the  arc)  perpendi- 
cular to  that  diameter,  touching  the  cir- 
cle, but  not  cutting  it,  and  terminated 
by  the  radius  of  the  circle  produced, 
and  passing  through  the  other  extre- 
mity of  the  arc. 

2.  Tangential  plane.  A  plane  which 
touches  a  curvilineal  solid.  It  is  from 
this  plane  that  we  measure  the  angles  of 
incidence  on  the  tangential  point,  whe- 
ther the  impinging  ray  be  reflected  or 
refracted. 

3.  Tangential  force.  Another  term  for 
centrifugal  force.  Thus,  when  two  forces 
act  upon  a  body, — the  centripetal  attract- 
ing the  body  towards  the  centre  of  gra- 
vity, the  tangential  driving  it  in  another 
direction,  there  will  result  a  curvilinear 
motion  around  the  central  point. 

TANNIC  ACID.  A  tribasic  acid  oc- 
curring in  the  bark  of  all  the  varieties  of 
Quercus  and  many  other  trees,  and  in 
gall-nuts,  from  which  it  is  procured  in 
greatest  purity.  What  is  commonly 
called  tannin  is  tannic  acid  mixed  with 
some  foreign  matters. 

TA'NTALUM.  Columbium.  A  metal 
found  in  the  two  Swedish  minerals,  tan- 
talite  and  yttrotantalite.  Its  name  is 
derived  from  the  insolubility  of  its  oxide 
in  acids,  in  allusion  to  the  fable  of  Tan- 
talus. 

TANTALUM  ORE.  Columbite  of 
Hatchett.  A  prismatic  ore  of  tantalum, 
occurring  as  a  coarse  red  granite  in  Fin- 
land. 

TA'NTALUS'S  CUP.  A  philosophical 
toy,  for  exhibiting  the  principle  of  the 
siphon.    The  siphon  is  placed  in  a  cup, 


TAR 


TAX 


and  its  legs  are  concealed  by  the  hollow 
figure  of  a  man  whose  chin  is  on  a  level 
with  the  bend  of  the  siphon,  so  that  the 
figure  stands,  like  Tantalus  in  the  fable, 
up  to  the  chin  in  water,  but  unable  to 
quench  his  thirst. 

TANY'STOMA  (ravixa,  to  stretch, 
arofia,  the  mouth).  A  section  of  dip- 
terous insects,  which  have  a  projecting 
proboscis,  with  the  last  joint  of  the  an- 
tennae undivided.  To  this  section  be- 
longs the  Gad-fly  tribe. 

TAP-ROOTED.  Fusiform.  A  desig- 
nation of  that  kind  of  root  which  consists 
of  one  fleshy  elongated  centre  tapering 
to  the  extremity.  This  is  termed 
pivotante  by  the  French. 

TA'PIRIRffi.  The  Tapir  tribe;  a 
group  of  Pachydermatous  animals,  differ- 
ing from  the  Suidae,  or  Pig  tribe,  in  the 
presence  of  only  three  toes  on  each  hind 
foot,  and  sometimes  also  in  the  front,  and 
in  the  absence  of  a  central  cleft  of  the 
foot. 

TAPITE'LJE  (tapetum,  a  carpet,  tela, 
a  web).  A  family  of  spiders,  which  spin 
great  webs  of  a  close  texture  like  ham- 
mocks, and  wait  for  the  insects  which 
may  be  entangled  therein. 

TA'RDIGRADA  (tardus,  slow,  gradus, 
a  step).  A  group  of  the  Edentata,  or 
toothless  animals,  distinguished  from  the 
true  edentata  by  the  peculiar  shortness 
of  the  muzzle.  They  are  characterized 
by  the  slowness  of  their  motion,  and  con- 
tain the  sloths,  in  which  Cuvier  ob- 
serves that  "  nature  seems  to  have 
amused  herself  with  producing  some- 
thing imperfect  and  grotesque." 

TARE,  TRET,  CLOFF,  &c.  These 
terms,  though  specially  of  commercial 
importance,  are  found  in  treatises  of 
arithmetic,  and  must  therefore  be  briefly 
noticed.  1.  Tare,  derived  from  the  Italian 
tarare,  to  abate,  is  the  allowance  made 
for  the  box  or  bag  in  which  goods  are 
packed.  2.  Tret,  probably  derived  from 
the  Italian  tritare,  to  crumble,  is  an 
allowance  of  41bs.  in  1041bs.  for  waste. 
3.  dnff,  or  clough,  defined  to  be  that 
wherein  any  thing  is  put  for  carriage 
sake,  is  an  allowance  of  21bs.  in  3cwt., 
in  order  that  the  weight  may  hold  good, 
when  the  article  is  sold  by  retail.  4.  Crross 
weight,  is  that  of  the  goods  and  the 
package  taken  together.  5.  Suttle,  pro- 
bably derived  from  the  Italian  sottile, 
fine  or  valuable,  denotes  the  weight 
which  remains,  when  the  tare  only  is 
allowed :  it  is  the  finer  part,  separated 
from  the  coarser.  6.  Net,  from  the  Italian 
329 


netto,  signifies  the  weight  which  remains 
when  all  allowances  are  made. 

TARRAS  or  TERRAS.  A  volcanic 
earth,  found  in  Germany  and  Sweden, 
and,  when  pulverised,  used  as  a  cement. 
It  does  not  differ  much  from  puzzolana, 
but  it  is  much  more  compact,  hard, 
porous,  and  spongy. 

TARSI.  The  feet  in  insects,  which 
are  articulated,  and  formed  of  five  or  a 
less  number  of  joints. 

TARTAR.  Bitartrate  of  potash;  a 
salt  deposited  on  the  sides  of  casks  dur- 
ing the  fermentation  of  wine,  owing  to 
its  insolubility  in  alcohol.  This  is  crude 
tartar,  and  it  is  also  called  argol ;  when 
purified,  it  is  called  cream  of  tartar. 

TARTARIC  ACID.  A  bibasic  acid, 
existing  in  many  fruits,  and  also  as  tar- 
trate of  lime  in  several  roots,  but  pre- 
pared only  from  the  juice  of  the  grape, 
which  contains  tartaric  acid  in  the  form 
of  tartar  or  bitartrate  of  potash. 

TARTARINE.  The  name  given  by 
Kirwan  to  the  vegetable  alkali,  or  potash. 

TARTRATE.  A  neutral  compound 
of  the  tartaric  acid  with  a  base. 

TAURUS.  The  Bull;  the  name  of 
the  second  zodiacal  constellation,  con- 
sisting of  141  stars,  the  principal  of 
which  is  Aldebaran.  It  denotes  the 
second  month  of  autumn,  extending 
from  the  20th  of  October  to  the  20th  of 
November,  and  the  period  of  tillage  in 
Egypt,  when  other  countries  have  done 
sowing. 

TAURUS  PONIATOWSKI.  A  mo- 
dern northern  constellation,  consisting 
of  seven  stars,  formed  by  a  Polish  astro- 
nomer, the  Abbe  Poczobut,  in  the  year 
1778.  It  is  situated  between  Aquila  and 
Ophiuchus. 

TAU'TOCHRONE  (rairo,  the  same, 
xoovos,  time).  A  term  in  Mechanics  for 
a  curve  line  having  this  property,  that  a 
heavy  body  descending  along  it  by  the 
action  of  gravity  will  always  reach  the 
lowest  point  in  the  same  time,  from 
whatever  point  in  the  curve  the  body 
begins  to  descend.  This  is,  under  cer- 
tain circumstances,  the  property  of  the 
cycloid. 

TAU'TOLITE.  A  crystalline  mineral, 
said  to  consist  of  silicate  of  protoxide  of 
iron  and  silicate  of  magnesia,  and  found 
in  the  volcanic  rocks  of  the  lake  of 
Laach,  near  Bonn,  on  the  Rhine. 

TA'XICORNS  (taxus,  the  yew,  cornu, 
a  horn).  A  family  of  coleopterous  in- 
sects, in  which  the  antennae  gradually 
increase  in  size   as  they   extend  from 


TEL 


TEL 


the  head,  or  terminate  in  an  enlarge- 
ment. 

TECTIBRANCHIA'TA  (tectus,  co- 
vered, branchice,  gills).  An  order  of 
aquatic  Gasteropods,  which  have  their 
branchiae  situated  on  the  back  or  on  the 
side,  and  concealed  or  covered  by  the 
mantle,  as  in  the  aplysia  and  the  pleuro- 
e  branchus. 

TEGMEN.  Literally,  a  covering; 
hence,  applied  by  Mirbel  to  the  internal 
integument  of  the  seed,  the  endopleura 
of  Decandolle  ;  and,  by  Palisot  de  Beau- 
vois,  to  the  glume  of  grasses. 

TEGME'NTA  (tegmentum,  a  covering). 
In  Botany,  the  scales  of  the  bud.  They 
are  termed  foliaceous,  when  they  consist 
of  abortive  leaves;  petiolaceous,  when 
they  are  formed  by  the  persistent  base  of 
the  petiole ;  stipulaceous,  when  they  arise 
from  the  union  of  stipules,  which  roll 
together  and  envelope  the  young  shoot; 
and  fulcraceous,  when  they  are  formed 
of  petioles  and  stipules  combined. 

TEI'NOSCOPE.  Prism  telescope.  An 
instrument  formed  by  combining  prisms 
in  a  particular  manner,  so  as  to  correct 
the  chromatic  aberration  of  light,  and  to 
increase  or  diminish  the  linear  dimen- 
sions of  objects  viewed  through  it. 

TELEGRAPH  (x^\e,  afar  off,  7p«0«, 
to  write).  An  apparatus  for  communi- 
cating intelligence  to  a  great  distance,  by 
means  of  signals  to  which  a  conventional 
meaning  is  attached.  A  telegraph  is  also 
called  a  semaphore  {anna,  a  sign,  (pepa, 
to  bear );  the  latter  term  is,  however, 
more  comprehensive  than  the  former,  as 
it  relates  to  the  communication  of  intel- 
ligence, not  merely  by  signals  resembling 
written  characters,  but  also  by  audible 
signals,  by  beacons,  and  other  pyrotechnic 
contrivances.     See  Tellograph. 

TELEGRAPH,  ELECTRICAL.  An 
apparatus  for  conveying  thought  by 
means  of  the  electric  current,  the  sig- 
nals being  given  by  the  different  actions 
of  the  current,  which  is  carried  from 
station  to  station  along  insulated  con- 
ductors. The  currents  are  excited  either 
by  hydro-electric  batteries,  or  by  mag- 
netic induction,  and  rotatory  machines ; 
the  telegraphic  signals  are  either  the  de- 
flections of  magnetized  needles,  or  the 
intermittent  excitation  of  magnetism  in 
electro-magnets,  or  the  physiological  phe- 
nomena. 

TELE'NGISCOPE  (tf}X«,  afar  off,  ly 
fvr,  near,  ano-irea,   to  see).     A  new  in- 
strument, combining  the  powers  of  the 
telescope  and  of  the  microscope. 
330 


TELEOSAU'RUS  (*eXeor,  perfect, 
aravpos,  a  lizard).  An  extinct  genus  of 
Saurian  reptiles,  characterized  by  a  com- 
bination of  a  bi-concave  structure  of  the 
vertebrae  with  long  narrow  jaws.  This 
genus,  and  that  of  the  steneosaurus,  have 
been  associated  together  by  Professor 
Owen,  the  characters  of  the  two  genera 
being  mainly  derived  from  the  difference 
of  position  in  the  external  nostril. 

TE'LESCOPE  {rTiKe,  afar  off,  c-K07rea>, 
to  see).  An  optical  instrument  for  dis- 
covering and  viewing  distant  objects. 
Astronomical  telescopes  are  of  two  kinds, 
refracting  and  reflecting ;  in  the  former, 
an  image  of  the  object  viewed  is  formed 
by  a  lens,  termed  the  object-glass,  which 
refracts  the  rays  from  the  object  into  one 
point ;  in  the  latter,  the  rays  of  light  are 
reflected  by  a  concave  speculum  or  mirror, 
by  which  an  image  of  the  object  viewed 
is  produced.  The  point  where  the  image 
is  distinctly  formed  by  the  lens  or  mirror 
is  the  focus ;  and  the  distance  of  this 
point  from  either  the  one  or  the  other 
is  the  focal  length  of  the  telescope. 

1.  Reflecting  telescopes  are  of  three 
kinds.  1.  The  Gregorian  has  a  hole 
pierced  in  the  centre  of  the  large  mirror  to 
receive  the  eye-piece ;  the  rays  from  the 
object  falling  on  the  large  speculum  are 
reflected  to  its  focus ;  there  they  are 
received  by  a  small  concave  mirror, 
whose  focus  coincides  with  that  of  the 
large  one,  and  reflected  through  the  aper- 
ture, where  they  are  received,  and  the 
image  magnified  by  the  eye-glass.  2.  The 
Cassegrainian  telescope  differs  from  the 
above  only  by  the  small  mirror  being 
made  convex  instead  of  concave.  3.  The 
Newtonian  telescope  has  no  aperture  in 
the  large  speculum,  but  the  rays  it  re- 
flects are  received  on  a  plane  speculum 
near  the  object  glass  of  the  tube,  which 
is  fixed  at  an  angle  of  45°  with  the  axis, 
and  by  it  are  reflected  to  the  side  of  the 
tube,  where  the  rays  are  brought  to  a 
focus  by  the  eye-glass.  The  telescope  of 
Lord  Rosse  is  constructed  on  this  prin- 
ciple. 

2.  Terrestrial  telescope.  The  inver- 
sion of  the  object  is  of  little  consequence 
when  the  instrument  is  employed  for 
astronomical  purposes,  for  since  the  forms 
of  the  heavenly  bodies  are  spherical,  their 
positions,  in  this  respect,  do  not  affect 
their  general  appearance.  But  for  ter- 
restrial purposes,  this  is  manifestly  a 
great  defect,  and  therefore  those  con- 
structed for  such  purposes  as  ship  or  spy 
glasses,  have  two  additional  lenses,  by 


TEM 


TEN 


means  of  which,  the  images  are  made  to 
appear  in  the  same  position  as  the  ob- 
jects.   These  are  called  double  telescopes. 

TELESCO'PIUM.  The  Telescope;  a 
modern  southern  constellation,  consist- 
ing of  nine  stars.  It  is  surrounded  by 
Ara,  Pavo,  Sagittarius,  and  Ophiuchus. 

TELLI'NIDjE.  Solid  and  closed  bi- 
valves :  a  family  of  the  macrotrachian 
mollusca,  in  which  the  two  siphons  of 
the  animal  are  of  enormous  length. 

TELLINI'NiE.  A  sub-family  of  the 
Tellinidce,  named  from  the  genus  tel- 
lina,  in  which  the  siphons  are  exces- 
sively long. 

TE'LLOGRAPH  (T^\e,  afar  off,  \670r, 
a  word,  fpd<p(o,  to  write).  This  term, 
contracted  from  telelograph,  is  used  by 
Edgeworth,  who  observes  that  while 
"  telegraph  is  a  proper  name  for  a  ma- 
chine which  describes  at  a  distance,  tele- 
lograph, or,  contractedly,  tellograph,  is  a 
proper  name  for  a  machine  which  de- 
scribes words  at  a  distance." 

TELLU'RIUM  {tellus,  the  earth).  A 
rare  metal  of  a  brilliant  silvery-white 
lustre,  found  in  abundance  at  Schemnitz, 
in  Hungary,  combined  with  bismuth; 
and  in  the  silver  mine  of  Sadovinski  in 
the  Altai,  united  with  silver  and  with 
lead.  With  oxygen,  it  yields  the  tel- 
lurous  and  the  telluric  acids. 

Telluretted  hydrogen.  A  gaseous  com- 
pound of  tellurium  and  hydrogen,  ana- 
logous in  constitution  and  properties  to 
sulphuretted  hydrogen. 

TEMPERAMENT  (tempero,  to  mix 
together,  to  temper).  Crasis.  A  mixture 
or  tempering  of  elements ;  a  notion 
founded  on  an  ancient  doctrine  of  four 
qualities,  supposed  to  temper  each  other  : 
these  are,  in  the  abstract,  hot,  cold,  dry, 
moist ;  in  the  concrete,  fire,  air,  earth, 
water. 

TEMPERAMENT,  EVEN.  A  musi- 
cal instrument  is  said  to  have  an  even 
temperament,  when  it  has  been  so  tuned 
that  the  differences  between  the  inter- 
vals are  perfectly  equalized.  To  accom- 
plish this,  the  difference,  must  be  so  dis- 
tributed among  all  the  semitones  of  the 
octave,  that,  when  sounded,  they  do  not 
bear  an  exact  ratio  to  any  fundamental 
note  whatever,  but  the  deviation  is  so 
small  a3  to  be  imperceptible. 

TEMPERATE  ZONES.  The  two  di- 
visions, or  belts,  of  the  surface  of  the 
earth,  which  lie  between  the  Tropics  and 
the  Polar  Circles— one  in  each  hemi- 
sphere. They  are  named  from  their  tem- 
perature being  free  from  the  excessive 
331 


heat  of  the  Torrid,  and  from  the  exces- 
sive cold  of  the  Frigid  Zones. 

TE'MPERATURE  (tempero,  to  mix 
various  things  in  due  proportions).  The 
comparative  degree  of  active  heat  accu- 
mulated in  a  body,  as  measured  by  an 
instrument,  or  by  its  effects  on  other 
bodies.  By  the  term  mean  annual  tempe- 
rature is  meant  the  temperature  obtained 
by  adding  together  the  temperatures  of 
all  the  months  of  the  year,  and  dividing 
the  sum  by  the  number  of  the  months ; 
so  that  the  mean  annual  temperature  ex- 
presses that  height  at  which  the  thermo- 
meter would  stand  at  any  place,  if  we 
could  suppose  it  perfectly  stationary 
throughout  the  whole  year. 

TEMPERING.  The  operation  of  heat- 
ing iron  to  a  certain  extent,  indicated  by 
the  colour  presented  on  the  surface  of 
the  metal. 

TEMPORARY  STARS.  Stars  which 
have  appeared,  from  time  to  time,  in 
different  parts  of  the  heavens,  blazing 
forth  with  extraordinary  lustre,  and,  after 
remaining  awhile  apparently  immove- 
able, have  disappeared  and  left  no  trace. 
Of  this  kind  was  the  star  which  appeared, 
a.d.  389,  near  a  Aquilae,  and,  after  re- 
maining for  three  weeks  as  bright  as 
Venus,  disappeared  entirely. 

TENA'CITY  {tenax,  capable  of  hold- 
ing). The  degree  of  force  with  which 
the  particles  of  bodies  cohere,  or  are  held 
together ;  a  term  particularly  applied  to 
metals  which  may  be  drawn  into  wire,  as 
gold  and  silver. 

TENDENCY.  This  word  is  employed 
in  two  senses.  By  a  '  tendency  '  towards 
a  certain  result  is  sometimes  meant,  '  the 
existence  of  a  cause  which,  if  operating 
unimpeded,  would  produce  that  result.' 
In  other  cases,  a  '  tendency'  towards  a 
certain  result  is  understood  to  mean  '  the 
existence  of  such  a  state  of  things  that 
that  result  may  be  expected  to  take  place.'' 
In  the  former  sense,  we  say  that  the 
earth  has  a  tendency  to  fly  off  at  a  tan- 
gent ;  but  in  the  latter,  the  earth  has  a 
greater  tendency  to  remain  in  its  orbit 
than  to  fly  off  from  it.  In  the  former 
sense,  it  may  be  said  that  population  has 
a  tendency  to  increase  beyond  subsist- 
ence ;  in  the  latter,  that  subsistence  has  a 
tendency  to  increase  at  a  greater  ratio 
than  population.     Whately. 

TENDRIL.  Cirrhus.  A  particular 
form  of  the  petiole  in  certain  plants,  as 
the  vine;  it  appears  to  be  a  contrivance 
employed  by  nature  to  support  plants  by 
the  aid  of  others,  and  was  included  by 


TER 


TER 


Linnaeus  among  the  class  of  fulcra,  or 
props. 

TE'NNANTITE.  Sulphuret  of  copper, 
occurring  in  Cornwall  in  copper  veins 
which  intersect  granite  and  clay-slate, 
associated  with  common  copper  pyrites. 
It  is  a  variety  of  grey  copper  ore,  and 
was  named  in  honour  of  Mr.  Smithson 
Tennant. 

TENOR  {teneo,  to  hold).  That  com- 
pass of  the  voice  which  is  hetween  the 
highest  and  the  lowest;  neither  raised  to 
a  treble,  nor  lowered  to  a  base,  but  rang- 
ing from  C,  the  second  space  in  the  base, 
to  G,  the  second  line  in  the  treble.  The 
term  alludes  to  the  air,  in  part-compo- 
sitions, being  held  by  the  tenor.  Tenor- 
clef  is  the  C,  or  mean  clef,  placed  on  the 
fourth  line  for  the  use  of  the  tenor  voice. 

TENSION  or  INTENSITY.  Terms 
employed  in  electricity  to  denote  the  de- 
gree to  which  a  body  is  excited,  as  esti- 
mated by  the  electrometer.  It  must  be 
distinguished  from  quantity. 

TENTA'CULA     (tentaculum,     from 
tento,  to  feel).    Feelers ;  organs  by  which 
certain  animals  attach  themselves  to  sur- 
rounding objects,  &c. 
V      TENTH.    An  interval  in  Music,  con- 
1  sisting  of  nine  degrees  and  five  spaces. 

TENTHREDI'NIDjE.  The  Saw-flies ; 
a  family  of  the  phytophagous  Terebrantia, 
named  from  the  genus  tenthredo,  and  cha- 
racterized by  the  saw-like  character  and 
operation  of  the  ovipositor.  By  Latreille, 
the  family  is  termed  Securifera,  or  the 
hatchet-bearers. 

TE'NUES  {tenuis,  thin).  The  correct 
distinction  of  the  letters  called  tenues,  as 
opposed  to  those  which  are  called  me- 
dial*, is,  perhaps,  this,  that  in  the  pro- 
nunciation of  the  tenues  p,  k,  t,  the 
organs  employed  in  articulation  have  only 
a  small  portion  of  their  surfaces  brought 
into  contact,  and  that  but  for  a  short 
time  ;  while  in  the  articulation  of  b,  g,  d, 
the  surface  in  contact  is  more  extensive, 
and  the  effort  less  rapid. 

TE'NUIRO'STRES  {tenuis,  slender, 
rostrum,  a  bill).  A  group  of  the  Inses- 
sores,  or  Perching  birds,  characterized  by 
a  very  slender  and  elongated,  straight  or 
curved,  bill.  They  include  the  hum- 
ming-birds, the  sun-birds,  the  hoopoes, 
the  honey-suckers,  and  the  birds  of  para- 
dise. 

TERCINE.  The  botanical  name  for 
the  epidermis  of  the  nucleus  of  the 
ovule,  when  it  separates  in  the  form  of  a 
third  coating  or  integument. 

TEREBRA'NTIA  {terebro,   to  bore). 
332 


A  section  of  Hymenopterous  insects, 
which  are  furnished  with  an  ovipositor, 
by  means  of  which  they  are  enabled  to 
bore  a  hole  in  certain  substances  for  the 
deposition  of  their  eggs.     See  Ovipositor. 

TE'REBRATING  {terebra,  a  perfo- 
rating instrument).  A  term  applied  to 
those  testaceous  animals  which  take  up 
their  abode  in  other  substances,  as  the 
pholas. 

TERGE'MINATE.  This  term  is  em- 
ployed, in  Botany,  when  each  of  two 
secondary  petioles  bears  towards  its  sum- 
mit one  pair  of  leaflets,  and  the  common 
petiole  bears  a  third  pair  at  the  origin  of 
the  two  secondary  petioles,  as  in  mimosa 
tergemina. 

TERM,  LOGICAL.  A  proposition 
consists  of  two  terms;  that  which  is 
spoken  of  is  called  the  subject ;  that  which 
is  said  of  it,  is  the  predicate  ;  and  these 
are  called  the  terms  (or  extremes),  be- 
cause, logically,  the  subject  is  placed 
first,  and  the  predicate  last.  In  the 
middle  is  placed  the  copula,  which  indi- 
cates the  act  of  judgment,  as  by  it  the 
predicate  is  affirmed  or  denied  of  the 
subject. 

Every  syllogism  has  three,  and  only 
three  terms :  viz.  the  middle  term,  and 
the  two  terms  (or  extremes,  as  they  are 
commonly  called)  of  the  conclusion  or 
question.  Of  these,  1st,  the  subject  of 
the  conclusion  is  called  the  minor  term ; 
2nd,  its  predicate,  the  major  term ;  and 
3rd,  the  middle  term  (called  by  the  older 
logicians  "  argumentum")  is  that  with 
which  each  of  them  is  separately  com- 
pared, in  order  to  judge  of  their  agree- 
ment or  disagreement  with  each  other. 
Whately. 

TERMS,  ALGEBRAICAL.  In  Alge- 
bra, those  parts  of  an  expression,  which 
are  connected  by  the  sign  -t-  or  — ,  are 
called  its  terms,  and  the  expression  itself 
is  said  to  be  simple  or  compound,  accord- 
ing as  it  contains  one  or  more  terms. 
Thus  a2  and  —  63  are  each  simple  quan- 
tities, and  a2  +  ab  —  i2  is  a  compound 
quantity,  whose  terms  are  a2,  +  ab,  and 
-63. 

When  one  quantity  is  said  to  be  ex- 
pressed in  terms  of  another,  the  expres- 
sion generally  means  merely  that  the 
former  is  to  be  an  explicit  function  of 
the  latter.  Thus,  in  x  +  y  =  a,  we  have 
expressed  x  +  y  in  terms  of  a;  deduce 
y  =  a—x,  and  we  have  y  expressed  in 
terms  of  a  and  x. 

TE'RMINAL.  "Term  is  a  word  of 
geometry  very  little  used,  and  signifying 


TER 


TES 


boundary  or  extremity ;  the  words  '  ter- 
minal value'  and  'terminal  form'  are 
sometimes  used  to  signify  the  last  and 
most  complete  value  or  form.  When  a 
finite  expression,  added  to  a  certain  num- 
ber of  terms  of  a  series,  makes  up  the 
equivalent  of  the  expression  from  which 
the  series  is  deduced,  or  stands  for  all 
the  subsequent  terms  of  the  series,  this 
finite  expression  might  be  called  the  ter- 
minal expression.  Thus,  in  Taylor's 
Theorem,  we  have  one  terminal  expres- 
sion in  D'Alembert's  form,  another  in 
that  of  Lagrange."    Pen.  Cycl. 

Terminal  Language.  "All  the  use  of 
the  terms  ■  infinitely  small'  and '  infinitely 
great'  is  entitled  to  this  name :  when  we 
say  that  a  circle  is  a  regular  polygon  with 
an  infinitely  great  number  of  infinitely 
small  sides,  the  language  used  is  that  of 
an  end  arrived  at,  a  transformation 
actually  made ;  the  circle  is  described  as 
actually  consisting  of  straight  lines ;  and 
the  language  is  terminal,  expressive  of  a 
boundary  actually  attained.  But  the 
meaning  of  this  language  is,  or  is  gene- 
rally held  to  be,  false ;  to  obviate  the 
difficulty,  terminal  language,  properly 
employed,  may  be  made  the  means  of 
abbreviation  of  all  those  truths  whose 
announcement  contains  interminable  ap- 
proximation."   Ibid. 

TERMINATE  and  INTERMINATE. 
A  terminate  number  is  an  integer,  a 
mixed  mumber,  or  a  vulgar  fraction.  As 
a  mixed  number  may  be  reduced  to  a 
vulgar  fraction,   all  terminate  numbers 

m 
may  be  expressed  by  — ,  where  m  and  n 

are  integers ;  and  when  the  number  is  an 
integer,  n  =  1,  and  the  number  =  m 

Interminate  Number.  A  number  which 
is  not  terminate,  is  called  an  interminate 
number.  Interminate  numbers  compre- 
hend interminate  decimals,  excepting 
repeaters  and  circulaters,  which  can  be 
reduced  to  vulgar  fractions,  and  are, 
therefore,  terminate  numbers,  although, 
however,  in  the  form  of  decimal  fractions, 
they  are  called  interminate  decimals. 

TERMINO'LOGY.  In  every  treatise 
of  science,  the  preliminary  part,  which  is 
devoted  to  the  explanation  or  definition 
of  the  terms  employed,  is  called  the  ter- 
minology of  that  science. 

TERMITIDiE  {termes,  the  white  ant). 
A  group  of  Neuropterous  insects  distin- 
guished from  the  dragon-flies  and  the 
day-flies  by  their  terrestrial  habits. 

TERMITPNjE.  A  section  of  neuro- 
pterous insects,  named  from  the  termes, 
333 


or  white  ant,  and  comprising  also  the 
genera  mantispa,  raphidia,  and  psocus. 
By  some  naturalists  these  genera  are 
considered  as  constituting  distinct  fami- 
lies. 

TERNARY.  A  term  applied  by  Dal- 
ton  to  any  chemical  substance  composed 
of  three  atoms.  By  ternary  compounds 
are  now  generally  understood  combina- 
tions of  binary  compounds  with  each 
other,  as  of  sulphuric  acid  with  soda  in 
Glauber's  salt,  and  the  salts  generally. 

TERNATE,  BITERNATE,  &c.  In 
Botanical  nomenclature,  these  terms  re- 
late to  the  composition  or  arrangement 
of  parts  upon  the  stem.  1.  Ternate  de- 
notes that  three  leaves  or  other  organs 
are  in  opposition  round  a  common  axis. 
2.  Biternate  signifies  that  three  secondary 
petioles  proceed  from  the  common  pe- 
tiole, and  that  each  bears  three  leaflets, 
as  in  fumitory.  3.  Triternate  implies 
that  the  common  petiole  is  divided  into 
three  secondary  petioles,  each  of  which 
is  subdivided  into  three  tertiary  petioles, 
each  of  the  latter  bearing  three  leaflets. 

TERRESTRIAL  MAGNETISM.  A 
term  denoting  the  action  of  the  magnetic 
fluid  in  or  about  the  earth  ;  the  effects  of 
that  action  being  manifested  in  the  phe- 
nomena presented  by  magnetized  needles 
or  bars. 

TERRI'COLA  {terra,  the  earth,  colo, 
to  inhabit).  An  order  of  the  Annellida, 
which  includes  the  earth  worms. 

TERTIARY  STRATA  A  series  of 
sedimentary  rocks,  with  characters  which 
distinguish  them  from  two  other  great 
series  of  strata— the  secpndary  and  the 
primary — which  lie  beneath  them. 

TERTIARY  SYSTEM.  A  compre- 
hensive geological  term,  representing  all 
the  regular  deposits  newer  than  the 
chalk.  It  admits  of  three  primary  divi- 
sions— eocene,  miocene,  and  pliocene — 
names  which  imply  that,  in  the  lowest 
division,  we  only  find  the  dawn  of  exist- 
ing species ;  that,  in  the  next  division, 
there  are  more  living  species,  but  that 
extinct  species  still  predominate ;  and 
that,  in  the  uppermost  division,  extinct 
species  decline,  and  living  species  pre- 
dominate. 

TE'SSELLATED  (tessella,  chequer- 
work).  Divided  into  squares  or  chequers, 
either  by  a  division  of  colours,  or  by  the 
crossing  of  stria?. 

TEST  {testis,  a  witness).  A  re-agent; 
a  substance  which,  when  added  to  an- 
other substance,  tests  or  distinguishes  its 
chemical  nature  or  composition.     Test 


TEU 


TEX 


paper  consists  of  letter-paper  dipped 
several  times  into  a  filtered  solution  of 
litmus,  and  dried  after  each  immersion, 
until  it  is  of  a  deep  purple  colour. 

TESTA.  Literally,  a  shell ;  and,  hence, 
applied  by  botanists  to  the  integuments 
of  the  seed.  By  Mirbel,  these  integu- 
ments are  called  lorica,  by  Richard  peri- 
sperm  and  episperm,  and  by  De  Candolle 
spermoderm.  It  appears  to  consist  of  two 
coats,  and,  in  succulent  seeds,  of  an 
intervening  substance  called  sarco- 
derm. 

TESTA'CEA  {testa,  a  shell).  Mol- 
luscous animals,  having  a  shelly  cover- 
ing, as  the  oyster. 

TESTUDI'NIDjE  {testudo,  a  tortoise). 
Land-tortoises  ;  a  family  of  Chelonian 
reptiles,  distinguished  by  their  highly 
arched  carapace,  and  short  clubby  feet. 

TETRABRANCHIA'TA  (Terpcic,  four, 
/?ptiYx<a,  gills).  An  order  of  Cepha- 
lopods,  represented  in  modern  times  by 
the  Pearly  Nautilus,  in  which  there  are 
four  branchial  organs,  two  on  each  side. 
See  Dibranchiata. 

TE'TRACHORD  (tctp«p,  four,  x°p3», 
a  chord).  The  Greek  name  for  any  part 
of  the  scale  of  music  consisting  of  four 
notes,  the  highest  of  which  is  a  perfect 
fourth  to  the  lowest. 

TETRADYNA'MIA  (rerpap,  four, 
bvvanis,  power).  The  fifteenth  class  of 
Linnaeus's  system  of  plants,  characterized 
by  the  presence  of  six  stamens,  of  which 
four  are  long,  two  short,  as  in  Stock. 

TE'TRAGOX  (rerpaf,  four,  7ama,  an 
angle).  A  figure  with  four  angles, 
usually  applied  jonly  to  the  square. 

TETRAHE'DRON  (rerpap,  four,  23pa, 
a  seat).  A  geometrical  solid  contained  by 
four  equal  and  equilateral  triangles. 

TETRA'MERA  {r*rpit,  four,  pepo?, 
a  part).  A  section  o'  Coleopterous  in- 
sects, in  which  all  the  tarsi  have  four 
distinct  joints,  the  fifth  being  very  mi- 
nute, and  concealed  in  the  others.  La- 
treille. 

TETRA'NDRTA  (TeTP«p,  four,  Av^p, 
mile).  The  fourth  class  of  plants  in 
Linnaeus's  system,  characterized  by  the 
presence  of  four  stamens  of  equal  length. 
See  Didynamia. 

TETRAO'NIDjE  (letrao,  the  grouse). 
The  Grouse  family  of  the  Rasores,  or 
Scratching  Birds,  characterized  by  their 
very  short  hind  toe  and  very  short  tail. 
They  differ  as  little  from  the  partridges 
as  these  from  the  pheasants.  They  vary 
much  in  size. 
TEU'THIME  (teuthis,  a  calamary).  A 
334 


family  of   Cephalopods,    of   which    the 
loligo  vulgaris,  or  teuthis,  is  the  type. 

TEXTURE  OF  ROCKS.  By  texture 
is  meant  the  mode  of  aggregation  of  the 
mineral  substances  of  which  rocks  are 
composed,  and  it  relates  to  the  arrange- 
ment of  their  parts  viewed  on  a  smaller 
scale  than  that  of  their  structure.  In 
this  respect  rocks  may  be  simple  or  com- 
pound, that  is,  composed  of  a  single  mine- 
ral species,  or  of  several  species.  Com- 
pound rocks  are  said  to  be  fragmentary, 
when  their  particles  or  fragments  are 
united  by  a  cement;  aggregated,  when 
their  particles  cohere  without  the  inter- 
vention of  a  cement. 

1.  The  texture  of  simple  rocks  is  said 
to  be,  1,  compact,  when  the  particles  or 
crystals  are  so  minute  as  not  to  be  dis- 
tinguished by  the  naked  eye,  as  in  some 
kinds  of  felspar  and  limestone ;  2,  earthy, 
when  the  particles  are  minute,  and  hav- 
ing little  cohesion,  readily  crumble,  as  in 
some  kinds  of  chalk  ;  3,  granular,  when 
the  particles  or  crystals  are  distinguish- 
able, and  of  a  rounded  form,  as  in  oolite ;  4, 
crystalline,  when  the  particles  are  readily 
distinguishable,  confusedly  aggregated, 
and  present  the  appearance  of  imperfect 
crystals,  as  in  primary  limestone ; 
5,  scaly,  when  the  particles  are  disposed 
in  the  form  of  small  scales,  as  in  some 
varieties  of  clay-slate  ;  6,  lamellar,  when 
the  rock  is  composed  of  very  thin  la- 
mellae, or  plates,  as  in  some  kinds  of 
pitchstone;  7,  laminar,  when  composed 
of  thin  parallel  laminae,  or  plates,  as  in 
clay-slate;  8,  fibrous,  when  composed  of 
very  elongated  slender  crystals,  as  in 
fibrous  gypsum;  and,  9,  radiated,  when 
the  fibres  present  a  radiated  or  divergent 
arrangement,  as  in  actinolite  slate. 

2.  The  texture  of  aggregated  compound 
rocks  is  said  to  be,  1,  compact,  when  the 
particles  are  so  minute,  as  to  give  the 
rock  a  dense,  homogeneous  appearance, 
as  in  some  kinds  of  granite  and  green- 
stone ;  2,  earthy,  as  in  lava ;  3,  granular, 
as  in  clay  and  marl  ;  4,  crystalline,  also 
called  granular  or  granitic  by  geologists, 
as    in    granite    and    hornblende    rock; 

5,  slaty,  as  in  gneiss,  mica-slate,  and 
chlorite-slate ;  this  texture  being  crystal- 
line in  the  compound  rocks,  but  with  the 
component  minerals  more  extended  in 
one  direction  than  in  another,  and  thus 
arranged  so  as  to  form  distinct  laminae; 

6,  porphyritic,  when  in  a  basis,  either 
crystalline  or  compact,  distinct  crystals 
are  interspersed,  as  in  various  kinds  of 
porphyry,  porphyritic  granite,  syenite,  and 


TH  A 


THE 


green-stone;  7,  amygdaloid,  when  in  a 
basis,  generally  compact,  sometimes  crys- 
talline or  earthy,  are  interspersed  roundish 
or  oval  bodies,  composed  of  one  or  more 
mineral  substances,  as  in  amygdaloidal 
clay-stone  or  green-stone  ;  and  8,  cavern- 
ous, presenting  numerous  small  cavities, 
roundish,  oval,  or  of  various  forms,  in  a 
compact  or  granular  rock. 

3.  The  texture  of  fragmentary  rocks  is 
said  to  be,  I,  brecciated,  when  it  consists 
of  angular  fragments,  cemented  together, 
constituting  breccia;  and,  2,  conglome- 
rated, when  it  consists  of  rounded  frag- 
ments of  quartz,  granite,  flint,  or  other 
substances  cemented  together,  forming 
conglomerate. 

THALAMIFLO'RjE  (thalamus,  a  bed, 
flos,  a  flower).  A  sub-class  of  Exogenous 
plants,  having  a  calyx  and  corolla,  petals 
distinct,  and  stamens  hypogynous.  Every 
part  of  the  flower  springs  separately 
from  the  thalamus,  without  contracting 
cohesion  with  each  other,  as  in  Ranun- 
culaceae. 

THA'LAMUS.  Literally,  a  bed;  and, 
hence,  the  term  is  applied  by  botanists 
to  the  dilated  summit  of  the  peduncle 
upon  which  the  carpels  are  seated ;  the 
term  is  synonymous  with  torus  and  with 
receptacle.  In  the  nomenclature  of  fun- 
gaceous  plants,  it  is  the  same  as  thallus, 
or  the  bed  of  fibres  from  which  many 
fungi  arise. 

THALASSI'NIANS.  A  family  of 
those  macrurous  decapods  which  have 
the  four  anterior  feet  terminated  by  two 
fingers,  and  are  remarkable  for  the  ex- 
treme elongation  of  the  abdomen  and  the 
small  degree  of  consistence  of  their  in- 
teguments. They  are  named  from  the 
genus  thalassina  of  Latreille. 

THALA'SSIOPHYTES  (OaXdaviov, 
belonging  to  the  sea,  <pvr6v,  a  plant). 
Sea-plants  ;  a  general  term  applied  to  the 
vegetable  productions  of  the  ocean,  of  its 
rocks  and  its  shores.  It  is  synonymous 
with  the  term  hydrophytes,  and  com- 
prises all  the  plants  usually  designated 
as  marine  algae,  viz.  fucus,  ulva,  &c. 

THALLUS.  A  terra  applied  to  the 
lobed  frond  of  lichens,  and  to  the  bed  of 
fibres  from  which  many  fungi  arise ;  it  is 
generally  employed  to  denote  the  com- 
bination of  stem  and  leaves  in  the  lower 
cryptogamic  plants.  Thallodes  is  the 
adjective  used  to  designate  any  thing 
arising  from  the  thallus. 

THAU'MATROPE  {OaZpa,  a  wonder, 
TpeTro),  to  turn).  A  philosophical  toy,  in 
which  two  objects  painted  on  opposite 
335 


sides  of  a  card, — as  a  man  and  a  horse,  a 
bird  and  a  cage, — are,  by  a  quick  rota- 
tory motion,  made  to  impress  the  eye  in 
combination,  so  as  to  form  one  picture, 
of  the  man  on  the  horse's  back,  the  bird 
in  the  cage,  &c.  A  mental  illusion 
closely  analogous  to  this,  is  produced, 
when  by  a  rapid  and  repeated  transition 
from  one  subject  to  another  alternately, 
— by  a  kind  of  intellectual  thaumatrope — 
the  mind  is  deluded  into  an  idea  of  the 
actual  combination  of  things  which  are 
really  incompatible.     Whately. 

THE'CA  {ef]Kn  a  capsule).  A  term 
applied,  in  Botany,  to  the  cavity  of  the 
anther,  to  the  sporangium  of  ferns,  to 
the  urn  of  mosses,  &c. 

THECADA'CTYLES  (6^**,  a  theca  or 
hollow  case,  SuktvAos,  a  toe).  The  name 
given  by  Cuvier  to  those  Geckos  which 
have  the  toes  enlarged  throughout  their 
length,  and  furnished  below  with  trans- 
verse scales,  which  are  divided  by  a 
longitudinal  furrow,  in  which  the  claw 
may  be  entirely  concealed. 

THE'CAPHORE  (0,>rj,  a  capsule, 
<p€pa>,  to  bear).  The  stalk  upon  which 
the  ovary  of  plants  is  sometimes  seated, 
as  in  tacsonia.  The  term  is  synonymous 
with  gynophore,  podogynium,  &c. 

THECODONTS  (fty**,  a  theca  or 
socket,  bdoi/i,  a  tooth).  This  and  some 
other  similar  terms  have  been  employed 
to  denote  the  leading  modifications  in  the 
mode  of  attachment  of  the  teeth  among 
the  inferior  or  squamate  saurians.  The 
base  of  the  teeth  may  be  either  ankylosed 
to  the  summit  of  the  alveolar  ridge,  or 
to  the  bottom  of  an  alveolar  groove,  and 
supported  by  its  lateral  wall.  These  mo- 
difications are  indicated  respectively  by 
the  terms  acrodont  and  pleurodont.  By 
a  third  mode  of  fixation,  the  teeth  are 
implanted  in  sockets,  either  loosely  or 
confluent  with  the  bony  walls  of  the 
cavity :  these,  Professor  Owen  calls  the- 
codont lacertians. 

THECO-SO'MATA  (O^n,  a  theca  or 
cavity,  cw/jlu,  a  body).  The  name  given 
by  De  Blainville  to  the  first  family  of 
Aporobranchiala,  or  those  molluscs  which 
are  provided  with  natatory  appendages, 
without  any  foot  properly  so  called,  and 
with  the  organs  of  respiration  but  little 
evident.  According  to  Mr.  J.  E.  Gray, 
the  thecosomata  constitute  the  first  order 
of  the  class  Pteropoda. 

THE'COSTOMES  (B^n,  a  cavity,  <tj6- 
/io,  the  mouth).  The  name  given  by 
Latreille  to  those  insects  which  have  a 
suctorious  mouth  enveloped  in  a  sheath. 


THE 


THE 


THELPHU'SIANS.  The  name  given 
by  Milne  Edwards  to  a  tribe  of  brachyu- 
rous  crustaceans  belonging  to  his  family 
Catometopes,  and  constituting  a  connect- 
ing link  between  the  Cancerians  and  the 
Gecarcinians,  or  land-crabs.  They  are 
named  from  the  genus  thelphusa,  sup- 
posed to  be  the  Heracleotic  crabs  of 
Aristotle. 

THE'NARDITE.  Anhydrous  sul- 
phate of  soda,  found  in  crystalline  crusts, 
at  the  bottom  of  the  briny  waters  at  the 
Salines  d'Espartines,  near  Madrid.  It  is 
used  in  the  preparation  of  carbonate  of 
soda. 

THEO'DOLITE.  An  instrument  for 
measuring  horizontal  angles  contained 
between  lines  supposed  to  be  drawn  from 
any  point  to  two  distant  objects.  In  its 
simplest  form,  the  theodolite  consists  of 
a  divided  circle,  which  is  to  be  set  parallel 
with  the  horizon  ;  and  a  telescope  which 
has  so  much  motion  in  a  vertical  plane  as 
to  enable  the  observer  to  view  any  object 
which  he  may  require  above  or  below  the 
horizon.  The  etymology  of  the  term  is 
obscure. 

THE'OREM  (fcwpujua,  that  which  is 
looked  at).  In  Mathematics,  a  theorem 
is  a  proposition  in  which  the  truth  of 
some  principle  is  asserted;  the  object  of 
the  demonstration  being  to  show  how  the 
truth  of  the  proposed  principle  may  be 
deduced  from  the  axioms  and  definitions, 
or  from  other  truths  which  have  been 
previously  and  independently  established. 
The  theorem,  asks  for  demonstration  only, 
and  thus  differs  from  the  problem,  which 
asks  for  discovery  both  of  method  and  of 
demonstration.     See  Problem. 

THEORY  {Oewpia,  speculation).  A 
system  of  rules,  intended  to  explain  cer- 
tain facts,  with  reference  to  some  real  or 
hypothetical  law.  Thus,  the  theory  of 
the  planetary  motions  is  deduced  from 
the  principle  of  gravitation ;  that  of 
light,  from  the  undulatory  hypothesis. 
A  hypothesis  differs  from  a  theory,  as 
being  an  assumption  conceived  to  afford 
a  support  to  the  re  d  or  supposed  law  : 
thus,  to  refer  the  phenomena  of  gravi- 
tation to  the  universal  diffusion  of  ether, 
is  a  hypothesis.  The  theory  is,  however, 
unaffected  by  the  hypothesis. 

THEORY  OF  COUPLES.  The  term 
couple  was  applied  by  M.  Poinsot  to  a 
pair  of  equal  and  opposite  forces,  not 
equilibrating  each  other,  and  not  capal  le 
of  being  replaced  by  a  single  force,  or 
resultant, — in  fact,  an  incomposible  cou- 
ple. The  plane  of  the  couple  is  the 
336 


plane  drawn  through  the  parallel  forces 
the  arm  of  the  couple  is  any  line  drawn 
perpendicular  to  the  forces  from  the  di- 
rection of  one  to  that  of  the  other,  the 
axis  of  the  couple  is  any  straight  line 
perpendicular  to  its  plane.  If  we  con- 
sider any  axis,  it  will  be  evident  that  the 
moment  or  leverage  of  the  couple  to  turn 
the  system  about  that  axis  is  represented 
by  the  product  of  one  of  the  forces  and 
the  arm.  For  if,  with  reference  to  the 
axis,  x  be  the  arm  of  one  of  the  forces, 
x  ±  a  is  that  of  the  other,  a  being  the 
arm  of  the  couple.  Hence,  if  P  be  one 
of  the  forces,  the  united  leverage  is 
P  {x  ±  a)  —  Pa;  or  ±  Pa.  This  product 
Pa  is  called  the  moment  of  the  cou- 
ple.    Pen.  Cycl. 

THEORY  OF  EQUATIONS.  The 
Theory  of  Algebraical  equations  is  that 
branch  of  analysis,  which  relates  to  the 
discussion  of  equations  when  presented 
in  their  most  convenient  form  for  solu- 
tion ;  and  its  great  object  is  to  develope 
the  properties  and  to  evolve  the  values  of 
the  real  and  the  imaginary  roots.  See 
Equation,  Algebraic. 

THERMAL  RAYS  {0epnn,  heat). 
Luminous  thermal  rays  are  those  rays  of 
heat  which  are  combined  with  flame,  as 
those  emitted  from  the  sun,  which  pene- 
trate all  diathermanous  substances. 
Those  rays,  on  the  contrary,  are  said  to 
be  opaque,  which  proceed  from  bodies 
heated  below  the  point  of  active  com- 
bustion. Hence,  bodies  are  either  per- 
fectly or  partially  diathermanous,  the 
former  transmitting  all  the  thermal 
colours,  the  latter  only  some  of 
them. 

THERMAL  SPECTRUM.  When 
Thermal  rays  have  been  transmitted 
through  a  diathermanous  prism,  they 
compose  a  thermal  spectrum,  in  like 
manner  as  the  sun's  rays  form  a  solar 
spectrum.     See  Spectrum. 

THERMO-ELECTRICITY  {Oepp.*, 
heat).  A  term  applied  to  the  phenomena 
which  are  exhibited  by  electricity  as  de- 
veloped by  heat.  The  condition  of  the 
electrical  equilibrium  of  bodies  is  dis- 
turbed by  heat,  especially  when  the  tem- 
perature of  a  part  of  their  mass  is  either 
raised  or  lowered  ;  the  effects  being  exhi- 
bited by  the  deflexions  of  a  magnetized 
and  balanced  needle. 

THERMO-MULTIPLIER  (0c?Piur), 
heat).  A  thermo-electric  pile,  employed 
by  Melloni  for  detecting  changes  of  tem- 
perature, and  endowed  with  much  greater 
sensibility  to  the    impressions  of  heat 


THE 


THE 


than  the  most  delicate  mercurial,  or  air 
thermometer. 

THERMOMETER  (0<=p/x»i,  heat,  ne- 
rpov,  a  measure).  Literally,  a  measurer 
of  heat;  an  instrument  for  comparing 
the  degree  of  active  heat  existing  in 
other  bodies,  by  its  effect  in  expanding 
a  column  of  mercury. 

1.  Fahrenheit's  Thermometer.  That 
arrangement  of  the  scale  of  the  instru- 
ment, in  which  the  space  between  the 
freezing  and  the  boiling  points  of  water, 
under  a  medium  pressure  of  the  atmo- 
sphere, is  divided  into  180  parts,  or  de- 
grees, the  freezing  being  marked  32°, 
and  the  boiling  212°.  This  scale  was 
adopted  by  Fahrenheit,  because  he  sup- 
posed, erroneously,  that  32  of  those  divi- 
sions below  the  freezing  point  of  water 
(which  was  therefore  0  on  his  scale)  was 
the  zero,  or  greatest  degree  of  cold. 

2.  Centigrade  Thermometer.  This  is 
the  thermometer  of  Celsius,  which  is 
used  in  France,  and  is  the  most  conve- 
nient in  practice  :  it  consists  in  that  ar- 
rangement of  the  scale,  in  which  the 
freezing  point  is  marked  0,  or  zero ;  and 
the  boiling  point  100. 

3.  Reaumur's  Thermometer.  In  this 
scale  the  freezing  point  is  marked  0,  or 
zero,  and  the  boiling  point  80°.  The 
degrees  are  continued  of  the  same  size, 
below  and  above  these  points,  those 
below  being  reckoned  negative. 

4.  These  different  modes  of  graduation 
are  easily  convertible:  the  Centigrade 
scale  is  reduced  to  that  of  Fahrenheit 
by  multiplying  by  nine  and  dividing  by 
rive ;  that  of  Reaumur  to  that  of  Fahren- 
heit by  dividing  by  four  instead  of  five : 
or  that  of  Fahrenheit  to  either  of  these, 
by  reversing  the  process.    Thus  — 

C.  100°  x  9=900-s-5  =  180 -I- 32°=212°F. 
R.    80°  x  9  =  720^4=  180 +  32°= 2 12°  F. 
Or,  by  reversing  the  order — 
F.  212°-32  =  180x  5  =  900-5-9=  100°  C. 
F.  212° -32= 180x4= 720-5-9=  80°  R. 

5.  A  Table  is  added,  showing  the  cor- 
respondence of  the  three  thermometers. 
Fahrenheit.    Centigrade.  Reaumur. 

212  100*      80- 

200 93-33  74-66 

190 87-77  70-22 

180  82-22  65-77 

170  7666  61  33 

160  71-11  56-88 

150  65-55  52  33 

140  60-       48* 

130  55-55  43-55 

120  48-88  3911 

110  43-33  3466 

337 


Fahrenheit.    Centigrade.         Reaumur. 

100  37-77  30  22 

90  32  22  25-77 

80  26-66  21-33 

70  2111   16-88 

60  15  55  12*44 

50  10-       8- 

40  4-44  3-55 

32  0-       0- 

20  -  6-66  -  5-33 

10  -12-22  -   9-77 

0  -17-77  -14-22 

6.  Thermometer,  Differential.  This 
instrument  consists  of  two  glass  bulbs, 
connected  by  a  glass  tube  bent  in  the 
form  of  the  letter  U.  The  tube  is  partly 
filled  with  a  coloured  liquid.  On  ex- 
posing one  bulb  to  heat,  the  expansion  of 
the  air  forces  the  liquid  down,  and  causes 
it  to  rise  in  the  opposite  part  of  the  tube. 
This  instrument  is  not  intended  to  indi- 
cate the  temperature  of  the  atmosphere, 
as  the  application  of  cold  or  heat  to  both 
bulbs  at  the  same  time  produces  no  alte- 
ration in  the  level  of  the  liquid ;  it 
merely  indicates  the  difference  of  tem- 
perature between  the  two  bulbs. 

7.  Thermometer,  Register.  An  instru- 
ment by  which  the  highest  and  lowest 
temperatures  which  occur  within  a  given 
time,  are  indicated  and  made  to  register 
themselves.  It  consists  of  two  thermo- 
meters placed  with  their  tubes  in  a  hori- 
zontal position.  The  one  contains  spirit 
of  wine,  the  other  contains  mercury.  In 
the  stem  of  the  former  a  small  iron  wire, 
placed  at  the  surface  of  the  mercury,  acts 
the  part  of  an  index,  being  propelled 
forward  as  the  mercury  expands,  and 
being  left  at  the  point  of  greatest  expan- 
sion, when  the  mercury  contracts  ;  it 
then  indicates  the  highest  temperature 
which  has  occurred  during  an  observa- 
tion. In  the  stem  of  the  latter  a  small 
piece  of  ivory  is  immersed  in  the  spirit, 
and  by  a  slight  inclination  of  the  instru- 
ment is  brought  to  the  surface  of  the 
liquid.  When  the  temperature  falls,  the 
ivory  is  carried  back  with  the  spirit ;  but, 
when  the  temperature  rises,  the  spirit 
only  advances,  the  ivory  being  left  be- 
hind, thus  indicating  the  lowest  tem- 
perature which  has  occurred.  By  in- 
verting the  thermometer,  the  ivory  is 
brought  again  to  the  surface  for  a  new 
observation. 

8.  Thermometer,  Magnetic.  An  appa- 
ratus for  employing  the  thermo-electric 
current  as  a  measurer  of  temperature  in 
cases  in  which  other  instruments  are  not 
sufficiently  delicate ;  or  in  cases  in  which 
Q 


THO 


THY 


the  temperatures  are  so  very  high  or  so 
very  low  that  our  ordinary  pyrometers 
and  thermometers  cannot  be  relied  on ; 
or,  lastly,  in  places  in  which  other  kinds 
of  apparatus  could  not  be  used.  The 
strength  of  the  current  generated  by  the 
heat  in  a  thermo-battery  measures  its 
temperature ;  the  intensity  of  the  cur- 
rent being  estimated,  as  in  hydro-electric 
batteries,  by  the  deflection  of  a  magnetic 
needle. 

THE'RMO  PHONE  (0eP|un.  heat,  <pd>vr], 
sound).  An  apparatus,  also  called,  from 
its  discoverer,  Trevelyan's  instrument, 
for  producing  sounds  from  heated  metals 
when  placed  under  certain  circum- 
stances. It  consists  of  a  metallic  body, 
generally  of  brass,  which  is  first  heated 
and  then  laid  on  a  cold  block  of  lead,  to 
which  it  gradually  imparts  its  heat ; 
during  the  process  of  cooling,  the  former 
bcdy  contracts  in  a  manner  by  regular 
pulsations,  and  in  so  doing  emits  musical 
sounds,  which  cease  entirely  when  the 
temperatures  of  the  two  metals  are 
equalized. 

THERMOSCOPE  (0<^/un,  heat,  <tko- 
n€<a,  to  observe).  The  name  of  a  parti- 
cular kind  of  thermometer,  which  shows 
or  exhibits  the  changes  of  heat  to  the  eye. 
So,  pyroscope  is  the  name  of  a  particular 
kind  of  pyrometer. 

THERMOSTAT  (0ep/tx»j,  heat,  tvrnfu, 
to  fix).  Heat-governor.  A  self-acting 
apparatus  for  regulating  temperature, 
constructed  on  the  principle  of  the  un- 
equal expansion  of  metals  by  heat. 

THIN  OUT.  A  term  employed  when 
a  geological  stratum,  in  the  course  of  its 
prolongation  in  any  direction,  becomes 
gradually  less  in  thickness;  the  two 
surfaces  approach  nearer  and  nearer, 
and  when,  at  last,  they  meet,  the 
stratum  is  said  to  thin  out  or  disap- 
pear. 

THIRD.  An  interval  in  music,  classed 
among  the  imperfect  concords,  from  its 
variable  nature,  as  it  may  be  either  major 
or  minor.  The  ratio  of  the  major  third 
is  5  I  4 ;  that  of  the  minor,  6  '.  5.  The 
former  comprises  one  major  and  one 
minor  tone,  as  CE;  the  latter,  a  major 
tone  and  a  semitone,  as  A  C. 

THO'MPSONITE.  A  mineral  of  the 
zeolite  family,  found  near  Kilpatrick. 

THORITE.  A  mineral  found  in 
syenite,  in  Norway,  containing  about 
58  per  cent  of  thorina. 

THO'RIUM.  A  metal  obtained  from 
a  black  mineral,  called  thorite,  from  the 
coast  of  the  North  Sea,  and  named  from 
338 


the  Scandinavian  deity  Thor.  Thorina 
is  considered  to  be  a  protoxide. 

THOROUGH-BASE.  A  technical 
term  expressive  of  the  art  of  playing 
an  accompaniment  on  keyed  instru- 
ments from  figures  representing  chords, 
and  placed  over  or  under  the  notes  of 
the  instrumental  base  staff. 

THREE,  RULE  OF.  The  name  given 
to  an  arithmetical  rule  which  teaches, 
from  three  given  quantities,  to  find  a 
fourth,  bearing  a  certain  relation  to  them. 
The  relation  is,  that  the  first  quantity 
shall  bear  the  same  proportion  to  the 
second  as  the  third  to  the  fourth,  or  the 
required  quantity.  The  rule  may  there- 
fore be  briefly  stated  to  be  that  by  which 
a  fourth  proportional  is  found  to  three 
given  quantities. 

Double  Rule  of  Three.  Questions  may 
arise  in  which,  instead  of  3  terms  given 
to  find  a  fourth,  we  may  have  5  given  to 
find  a  sixth.  The  rule  in  such  cases 
might  be  called  the  Rule  of  Five.  "  Write 
the  given  quantities  in  two  lines,  keep- 
ing quantities  of  the  same  sort  under 
one  another,  and  those  which  are  con- 
nected with  each  other  in  the  same  line. 
Draw  a  curve  through  the  middle  of 
each  line  and  the  extremities  of  the 
other.  There  will  be  three  quantities  on 
one  curve  and  two  on  the  other.  Divide 
the  product  of  the  three  by  the  product 
of  the  two,  and  the  quotient  is  the  an- 
swer to  the  question."    Be  Morgan. 

THULITE.  A  mineral,  usually  granu- 
lar, found  in  Norway,  and  consisting 
principally  of  silica,  alumina,  and  lime. 

THU'MERSTONE.  A  mineral  found 
in  beds  at  Thum  in  Saxony.  It  is  also 
called  axinite,  from  the  axe-like  form 
and  edge  of  its  crystals. 

THUNDER.  This  phenomenon  is 
supposed  to  be  occasioned  by  the  sudden 
rushing  of  the  air  into  a  partial  vacuum 
produced  by  the  heat  of  lightning.  For 
its  prolongation,  various  causes  have 
been  assigned. 

THYRSUS.  A  form  of  inflorescence, 
consisting  of  a  compact  panicle,  the 
middle  branches  of  which  are  longer 
than  those  of  the  apex  or  of  the  base,  as 
in  lilac.  The  thyrsus  has  been  also  de- 
fined as  an  inflorescence  at  first  centri- 
petal, afterwards  centrifugal. 

THYSANO'URA  {0v*<tu>,  obsolete ; 
from  0u<o,  to  move  rapidly,  ol>pa,  a  tail). 
The  Spring-tails ;  an  order  of  insects 
which  jump  by  means  of  their  tail.  They 
are  wingless,  and  do  not  undergo  meta- 
morphosis. 


TIN 


TOI 


TIDES.  A  term  applied  to  the  pe- 
riodic rising  and  falling  of  the  ocean, 
caused  chiefly  by  the  attraction  of  the 
moon,  but  partly  by  that  of  the  sun. 
The  sea  flows,  or  rises,  as  often  as  the 
moon  passes  the  meridian,  both  the  arc 
above,  and  the  arc  below  the  horizon ; 
and  it  ebbs,  or  falls,  as  often  as  she  passes 
the  horizon,  both  east  and  west.  When 
the  moon  is  in  the  first  and  third  quarter, 
i.  e.,when  she  is  new  and  when  she  is  full, 
or,  in  other  words,  when  she  is  in  con- 
junction or  in  opposition,  the  tides  are 
high  and  swift,  and  are  called  spring- 
tides ;  when  she  is  in  the  second,  and  last 
quarter,  i.  e.,  when  she  is  a  half-moon, 
or  in  her  quadratures,  the  tides  are  lower 
and  slower,  and  are  called  neap-tides. 

TILE  ORE.  A  sub-species  of  octo- 
hedral  red  copper  ore.  An  earthy  variety 
occurs  massive  and  incrusting  copper 
pyrites  ;  the  indurated  variety  is  an  inti- 
mate combination  of  red  copper  ore  and 
brown  iron  ochre. 

TILGATE  BEDS.  The  name  given 
by  Dr.  Mantell  to  a  portion  of  the  great 
series  of  strata  in  the  Weald  of  Kent  and 
Sussex,  interposed  between  the  green- 
sands  and  the  Portland  oolite. 

TIME.  A  certain  measure  of  dura- 
tion, depending  upon  the  motion  of  the 
heavenly  bodies. 

1.  Equal  or  mean  time,  is  that  which 
is  reckoned  by  a  clock,  supposed  to  indi- 
cate exactly  24  hours,  from  12  o'clock 
on  one  day,  to  12  o'clock  on  the  next  day. 

2.  Apparent  time,  is  that  which  is 
measured  by  the  apparent  motion  of  the 
sun  in  the  heavens,  as  indicated  by  a 
meridian  line,  or  sun-dial. 

3.  Sidereal  time  is  that  portion  of  a 
sidereal  day  which  has  elapsed  since  the 
transit  of  the  first  point  of  Aries,  and 
represents  at  any  moment  the  right 
ascension  of  any  object  which  is  then  on 
the  meridian. 

4.  Astronomical  time  of  day  is  the 
time  past  mean  noon  of  the  day,  and  is 
reckoned  on  to  twenty-four  hours  in 
mean  time. 

5.  Civil  time  is  mean  time  adapted  to 
the  purposes  of  civil  life.  The  civil  day 
commences  at  midnight,  and  is  divided 
into  twelve  hours  marked  a.m.  or  ante 
meridian,  and  twelve  marked  p.m.  or 
post  meridian. 

TIN.  Stannum.  A  white  metal  ob- 
tained from  the  peroxide,  or  common 
ore,  called  stream-tin.  The  purer  por- 
tion of  the  metal  thus  obtained,  is  called 
grain  tin,  the  other  portion  ordinary  tin 
339 


or  block  tin.  The  metal  is  found  asso- 
ciated with  sulphur  and  copper,  consti- 
tuting tin  pyrites ;  when  combined  with 
oxide  of  iron  and  silex,  it  is  called  tin- 
stone and  wood-tin.  The  protoxide  and 
the  peroxide  are  named,  respectively, 
the  stannous  and  the  stannic  oxide. 

TIN-FOIL.  An  alloy  composed  chiefly 
of  tin,  with  a  small  portion  of  lead,  and 
sold  in  the  form  of  a  leaf  of  about  the 
l-1000th  part  of  an  inch  in  thickness. 

TINCAL.  Crude  borax,  as  it  is  im- 
ported from  the  East  Indies,  in  yellow 
greasy  crystals.  When  purified,  it  con- 
stitutes the  refined  borax  of  commerce. 

TFNEID^E  (tinea,  a  moth).  A 
family  of  Lepidopterous  insects,  consist- 
ing of  small  moths,  which  infest  woollen 
stuffs  and  furs,  upon  which  their  larvae 
feed. 

TIPU'LIDjE.  A  family  of  dipterous 
insects,  belonging  to  the  section  Nemo- 
cera,  and  typified  by  the  species  com- 
monly called  Harry-long -legs. 

TISSUE.  A  web,  or  web-like  struc- 
ture, constituting  the  elementary  struc- 
tures of  animals  and  of  plants. 

TITAN-SHORL.  Rutile.  Native 
oxide  of  titanium,  a  mineral  comprising 
the  reticulated  variety  with  golden  var- 
nish, from  Moutier,  near  the  Montblanc  ; 
acicular  and  capillary  crystals  of  rutile 
in  rock  crystal,  from  Brazil,  &c. 

TITANFFEROUS  CERITE.  A 
blackish-brown  mineral,  found  on  the 
Coromandel  coast,  and  consisting  of  the 
oxides  of  cerium,  iron,  manganese,  and 
titanium. 

TITANITE.  Sphene.  Silico-titanite 
of  lime,  comprising  the  varieties  of 
brown  and  yellow  menakan-ore,  in  large 
crystals ;  and  that  from  St.  Gothard 
denominated  rayonnante  en  gouttiere  by 
Saussure,  on  felspar  with  chlorite,  &c. 

TITANIUM  (T.Vai/o?,  calx).  A  metal 
which,  in  the  form  of  titanic  acid,  con- 
stitutes several  minerals,  as  menachan- 
ite,  &c. 

TOADSTONE.  A  provincial  term 
applied  to  certain  igneous  or  basaltic 
rocks  associated  with  the  limestone 
formation  of  Derbyshire. 

TO'DIDjE.  The  Todies;  a  family 
of  the  Insessores,  or  Perching  birds,  in- 
digenous in  America,  where  they  may  be 
regarded  as  representing  the  king-fishers 
of  the  Old  Continent.    See  Fissirostres. 

TOISE.     Orgya.    A   French  measure 

of  length,  consisting  of  six  feet,  or  the 

ordinary  height  of  man.  It  is  employed  in 

all  the  older  French  measures  of  the  earth. 

Q2 


TOR 


TR  A 


TOMBAC.  A  white  alloy  of  copper 
with  arsenic,  called  white  copper. 

TOME'NTUM.  A  term  applied,  in 
Botany,  to  the  hairs  of  plants,  when  they 
are  entangled,  and  closely  pressed  to  the 
stem. 

TOOTHED  WHEELS.  Wheels  which 
are  made  to  act  upon,  or,  as  it  is  called, 
to  drive  one  another  by  having  the  sur- 
face of  each  indented  with  teeth,  and 
fixing  the  centres  at  such  a  distance  from 
each  other  that  the  teeth  come  succes- 
sively into  contact.  The  proper  form  for 
the  tooth  of  such  wheels  is  a  question  of 
much  complexity. 

TOOTHINGS  OF  LEAVES.  The  pro- 
jecting parts  of  the  margin  of  leaves, 
when  the  adhesion  of  the  lobes  is  com- 
plete, and  the  parenchyma  which  sepa- 
rates the  extremity  only  of  the  veins  is 
not  extended  to  the  extremity  of  the 
principal  veins,  or  beyond  them.  Such 
leaves  are  said  to  be  toothed  or  dentate ; 
and,  when  the  teeth  or  toothings  are 
rounded,  they  become  crenels,  and  the 
leaf  is  said  to  be  crenelled  or  crenate. 

TOPAZ  (rondCtov).  A  mineral  species 
occurring  massive  in  imbedded  and 
rounded  crystals.  It  forms  an  essential 
constituent  of  a  particular  mountain - 
rock,  which  is  an  aggregate  of  topaz, 
quartz,  and  schorl,  and  is  called  topaz- 
rock.  It  comprises  three  sub-species, 
common  topaz,  schorlite,  and  physalite. 

TOPA'ZOLITE.  A  variety  of  pre- 
cious garnet,  found  at  Mussa,  in  Pied- 
mont. 

TOPO'GRAPHY  (totto?,  a  place, 
7pa0o),  to  describe).  The  description  of 
a  place,  as  of  a  city,  a  town,  a  village ;  a 
term  differing  from  geography,  as  a  part 
ditFers  from  the  whole. 

TORNA'DO  {iornar,  Span,  to  turn). 
A  sudden  and  violent  storm  of  wind, 
accompanied  by  thunder,  lightning,  and 
rain,  frequently  occurring  in  the  West 
Indies,  and  other  parts.  The  term  also 
denotes,  generally,  a  typhoon  or  hurri- 
cane. 

TO'RRELITE.  A  red  mineral  from 
New  Jersey,  named  from  Dr.  Torrey,  and 
consisting  principally  of  silica,  iron,  and 
lime. 

TORRICELLIAN  EXPERIMENT. 
The  name  given  to  the  experiment  by 
which  Torricelli,  a  pupil  of  Galileo,  dis- 
covered that  the  mercury  remains  in  the 
barometer  tube  at  a  height  of  nearly 
30  inches  above  the  level  of  the  mercury 
in  the  cistern.  The  tube  was  hence 
called  a  Torricellian  tube,  and  the  vacuum 
340 


in  the  tube  above  the  surface  of  the 
mercury  is  the  Torricellian  vacuum,  by 
which  name  it  is  distinguished  from  that 
obtained  by  the  air-pump,  sometimes 
called  the  Guerickian  or  Boylean  va- 
cuum. 

TORRID  ZONE  {torridus,  burning). 
That  division,  or  belt,  of  the  surface  of 
the  earth,  which  lies  on  each  side  of  the 
equator,  extending  to  the  two  tropics  of 
Cancer  and  Capricorn,  and  so  called  from 
its  excessive  heat.    See  Ascii. 

TORSION  BALANCE.  An  instru- 
ment, invented  by  Coulomb,  for  the  mea- 
surement of  small  attractive  and  repul- 
sive forces,  by  the  torsion  or  twisting  of 
a  fine  metallic  wire.  The  electrical  tor- 
sion balance  is  made  of  a  thin  thread  of 
shellac,  carrying  at  its  extremity  a  small 
gilded  pith  ball ;  this  instrument  forms 
a  very  delicate  electrometer,  and  is  also 
employed  for  estimating  exactly  the  in- 
tensity of  magnetic  forces. 

TORUS.  A  rope  or  cord  made  of 
twisted  grass  or  straw,  on  which  the 
ancients  laid  their  skins  or  other  furni- 
ture for  the  convenience  of  sleeping; 
hence  the  term  is  taken  for  a  bed,  and  is 
used  in  botany  as  synonymous  with 
thalamus  or  receptacle. 

TO'TIPALMES  (tota  palma,  an  entire 
palm).  The  name  given  by  Cuvier  to  a 
group  of  birds  whose  hind  toe  is  united 
to  the  others  by  a  continuous  membrane  ; 
they  comprise  the  pelican,  the  cormorant, 
the  boobies,  the  frigate-birds,  &c. 

TOUCAN.  A  modern  southern  con- 
stellation, consisting  of  nine  stars. 

TOUCHSTONE.  A  variety  of  flinty- 
slate,  frequently  called  Lydian  stone. 

TOURMALINE.  Schorl.  A  mineral 
which  is  hard  enough  to  scratch  glass, 
and  becomes  electric  by  heat.  It  is  of 
various  colours  and  forms ;  the  blue 
variety  being  called  indicolite,  and  the 
red  rubellite ;  it  is  transparent  when 
viewed  across  the  thickness  of  a  crystal, 
but  perfectly  opaque  when  turned  in  the 
opposite  direction.  The  ancients  called 
it  lyncurium.  It  occurs  in  gneiss,  mica- 
slate,  talc-slate  &c. 

TRACHEA'TA  (rpaxela,  the  trachea). 
An  order  of  the  Arachnida,  comprising 
those  species  which  breathe  by  means  of 
tracheae.     See  Pulmonata. 

TR ACHE'LI  DES  (Tpaxn^oc,  the  neck). 
A  family  of  the  heteromerous  Coleoptera, 
in  which  the  head  is  separated  from  the 
thorax  by  a  kind  of  neck.  They  are 
often  of  brilliant  colours,  as  the  blister- 
ing-fly. 


TR  A 


TRA 


TRACHE'LIPODS  (rpaxnW,  the 
neck,  now,  nodos,  the  foot).  A  designa- 
tion of  those  mollusca  which  have  the 
locomotive  disc  or  foot  attached  to  the 
head.  Under  this  title,  which  represents 
the  third  order  of  Lamarck,  all  the  uni- 
valved  shells  are  arranged. 

TRACHE'NCHYMA  (rpaXela,  the 
trachea,  £yxuMa>  anY  thing  poured  in). 
A  designation  of  the  vascular  tissue  of 
plants,  consisting  of  spiral  vessels,  which 
resemble  the  trachea  of  insects. 

TRA'CHYLITE.  The  name  of  a 
mineral  substance  resembling  obsidian. 

TRA'CHYTE  (TpaXv?,  rough).  A 
variety  of  lava  essentially  composed  of 
glassy  felspar,  and  frequently  having 
detached  crystals  of  felspar  in  the  base 
or  body  of  the  stone,  giving  it  the  struc- 
ture of  porphyry.  It  sometimes  contains 
hornblende  and  augite ;  and  when  these 
predominate,  the  trachyte  passes  into  the 
varieties  of  trap  called  greenstone,  ba- 
salt, dolorite,  &c.  The  term  is  derived 
from  the  peculiar  rough  feel  of  the 
rock. 

TRACTION  {tractio,  drawing).  In 
Mechanics,  the  act  of  drawing  a  body 
along  a  plane,  by  the  power  of  animals 
or  of  steam.  The  angle  of  traction  is  the 
angle  which  the  direction  of  the  power 
makes  with  a  given  plane.  The  power 
excited  to  produce  the  effect  is  called 
the  force  of  traction.    See  Horse-power. 

TRA'CTRlX  or  TRACTORY.  A 
curve  described  by  a  heavy  point  attached 
to  a  string,  the  other  end  of  which  is 
moved  along  a  given  straight  line  or 
curve.  It  is  characterized  by  this  pro- 
perty, that  the  tangent  is  always  equal  to 
a  given  line. 

TRADE  WINDS.  In  a  belt  extend- 
ing  about  30°  on  each  side  of  the  equator, 
the  wind  is  observed  to  blow  all  the  year 
round  from  nearly  the  same  quarter  of 
the  heavens  :  to  the  north  of  the  equator 
it  blows  nearly  from  the  n.e.  quarter, 
and  to  the  south  of  the  equator  from  the 
s.E.  quarter.  These  winds,  from  the  great 
assistance  which  they  afford  to  commerce, 
are  called  the  n.e.  and  the  s.e.  trade 
winds.  '  When  ships  are  bound  from 
Europe  to  the  West  Indies,  or  to  any  part 
of  North  America,  south  of  the  parallel 
of  about  38°,  they  seek  the  aid  of  these 
winds ;  but  when  they  return,  they  keep 
away  to  the  northward  for  the  purpose 
of  avoiding  them. 

TRAJE'CTORY.  A  technical  name 
formerly  given  to  a  curve  required  to  be 
found  by  means  of  certain  conditions ; 
341 


generally  used  for  the  required  path  of  a 
projectile  acted  on  by  given  forces. 

TRAMMELS.  Elliptic  compasses, 
used  for  making  figures  of  an  elliptfe 
form.  In  this  instrument,  a  bar  carry- 
ing a  pencil  is  guided  by  two  pins  which 
move  in  grooves. 

TRANSCENDE'NTAL  (transcendo,  to 
go  beyond  a  certain  limit).  In  the  phi- 
losophy of  Kant,  the  transcendental  ele- 
ments of  knowledge  are  those  which  are 
original  or  primary,  or  those  which  are 
determined  &  priori  in  reference  not  only 
to  human  cognition,  but  also  to  man's 
collective  activity;  and  which,  conse- 
quently, are  the  basis  of  empirical  know- 
ledge, or  that  which  is  determined  d, 
posteriori.  In  short,  all  pure  knowledge 
makes  up  the  transcendental  philosophy, 
and  on  it  rest  the  authority  and  possi- 
bility of  cognition.  The  term  is  thus 
synonymous  with  metaphysical. 

A  transcendental  problem,  according  to 
the  earliest  meaning  of  the  term,  is  one 
the  equation  of  which  is  infinitely  high, 
or  contains  an  infinite  series  of  powers  of 
an  unknown  quantity,  so  that  its  highest 
degree  transcends  every  degree.  But 
the  term  transcendental  has  undergone 
many  changes  of  meaning.  The  writers 
in  the  Penny  Cyclopaedia  predict  that 
it  will  settle  into  the  following  :  "  a  tran- 
scendental result  will  be  one  which  is 
incapable  of  expression,  except  by  a 
definite  integral,  or  by  an  infinite  series 
which  cannot  be  otherwise  expressed 
than  by  a  definite  integral." 

TRANSFORMATION.  A  term  in 
Mathematics  denoting  a  change  made  in 
the  object  of  a  problem  or  in  the  shape 
of  a  formula,  in  order  to  facilitate  the 
solution,  calculation,  or  use  of  the  ori- 
ginal problem  or  formula ;  as  when  an 
equation  is  transformed  into  another 
equation,  having  roots  which  bear  simply 
a  relation  to  the  roots  of  the  former.  All 
the  operation  of  Algebra  consists  in  trans- 
formation, from  and  after  the  point  at 
which  the  problem  to  be  solved  is  re- 
duced to  an  equation. 

TRANSIT  {transeo,  to  pass  over).  In 
Astronomy,  this  term  denotes  the  pas- 
sage of  one  heavenly  body  over  the  disc 
of  a  larger  one,  as  that  of  Mercury,  when 
he  transverses  the  sun's  disc  under  the 
form  of  a  black  spot.  When  the  nearer 
body  has  the  greater  apparent  diameter, 
so  as  to  hide  the  other,  the  passage  is 
termed  an  occultation  of  the  latter. 

TRANSIT  INSTRUMENT.     Instru- 
ment des  Passages,    An  instrument  by 
Q3 


TR  A 


TRA 


means  of  which  the  culminations  of  ce- 
lestial objects  are  observed.  It  consists 
of  a  telescope  firmly  fastened  on  a  hori- 
zontal axis  directed  to  the  east  and  west 
points  of  the  horizon,  or  at  right  angles 
to  the  plane  of  the  meridian  of  the  place 
of  observation. 

TRANSITION  SERIES.  Submedial 
rocks.  A  geological  designation  of  the 
upper  metamorphic  rocks,  which  form  a 
kind  of  link  between  the  primary  and 
the  secondary  rooks,  partaking  of  the 
characters  of  both.  They  are  divided 
into  two  series  or  systems,  the  Greywacke 
and  the  Silurian. 

TRANSLATION.  This  word  is  used 
in  Mechanics,  as  distinguished  from  Ro- 
tation, in  the  following  manner: — A 
body  has  motion  of  translation  when  all 
its  points  move  in  parallel  straight 
lines  ;  when,  in  fact,  all  its  points  have 
the  same  motion.  If  all  have  not  the 
same  motion,  there  is  either  simple 
rotation,  that  is,  about  one  permanent 
axis ;  or  rotation  about  a  varying  axis ; 
or  else  a  compound  of  translation  and 
rotation.  The  motion  of  a  single  point 
must  always  be  called  translation,  rota- 
tion being  an  inadmissible  idea. — Pen. 
Cycl. 

In  Geometry,  the  word  translation  has 
a  wider  sense;  perhaps,  transference 
might  be  a  preferable  term,  as  applied  to 
the  motion  of  a  figure  from  one  part  of 
space  to  another.  The  case  meets  us  at 
the  fourth  proposition  of  the  First  Book  of 
Euclid's  Elements,  in  which  we  have  to 
conceive  of  one  figure  being  transferred 
by  some  means ;  for  it  is  impossible  to 
imagine  space  removed,  or  any  part  of 
space  made  to  change  place. — Ibid. 

TRANSLU'CENT  and  TRANSPA'- 
RENT.  1.  Translucent  bodies  are  those 
which  permit  light  to  pass  through  them, 
but  not  in  sufficient  quantity  to  render 
objects  distinct,  as  to  colour,  distance,  or 
form,  when  viewed  through  them.  2. 
Transparent  bodies  are  those  which  per- 
mit the  rays  of  light  to  pass  freely 
through  them,  as  air  and  some  of  the 
gases,  which  transmit  light  without 
being  visible  themselves  :  glass  and 
water  are  less  transparent.  Translucent 
bodies  might  be  termed  semi-transpa- 
rent. 

TRANSMUTATION.  The  alchemi- 
cal operation  of  changing  the  imperfect 
into  the  perfect  metals.  In  geometry,  the 
changing  of  one  figure  into  another  of 
equal  area  or  content,  as  of  a  triangle 
into  a  square,  of  a  sphere  into  a  cube. 
342 


TRANSPOSITION.  In  Algebra,  the 
process  of  removing  or  transposing  a 
term  from  one  side  of  an  equation  to  the 
other,  at  the  same  time  changing  its 
sign.  Thus,  the  equation,  a  =  b  +  c 
becomes,  by  transposition  of  c,  the  equa- 
tion a—c=b,  the  value  of  which  is  pre- 
cisely the  same  as  that  of  the  preceding. 
The  process  amounts  to  merely  subtract- 
ing c  from  both  sides  of  the  equation. 

TRANSVE'RSAL.  The  name  given 
in  Mathematics  to  a  line,  whether  right 
or  curved,  which  is  drawn  across  or  in- 
tersects a  system  of  other  lines,  right  or 
curved 

TRANSVERSE.  The  name  frequently 
given  to  one  of  the  axes  of  a  figure, 
usually  that  of  the  greater  magnitude  or 
which  goes  across  the  figure.  Thus,  the 
longer  axis  of  an  ellipse  or  of  a  hyper- 
bola is  the  transverse  axis ;  the  equato- 
rial axis  of  the  globe  is  the  transverse. 
Properly  speaking,  the  term  is  merely 
relative :  each  axis  is  transverse  to  the 
other. 

TRANSVERSE  MAGNET.  A  pecu- 
liar variety  of  bar  magnets,  whose  poles 
are  not  at  the  ends,  but  at  the  sides  : 
these  magnets  have  always  some  even 
number  of  polar  lines.  They  are  made 
by  thrusting  2,  4,  6,  &c.  bar  magnets 
through  a  ring  in  the  direction  of  its 
diameter,  and  with  their  unlike  poles 
opposite  to  each  other;  a  sufficient  space 
is  left  between  these  magnets  to  pass  the 
bar  between  them  which  it  is  proposed 
to  magnetise,  so  that  it  may  touch  them 
as  it  is  drawn  through. 

TRAP  and  TRAPPEAN  ROCKS 
(trappa,  Swedish,  a  stair).  Volcanic  rocks 
composed  of  felspar,  augite,  and  horn- 
blende. The  various  proportions  and 
state  of  aggregation  of  these  simple  mi- 
nerals, and  differences  in  external  forms, 
give  rise  to  varieties,  which  have  received 
distinct  appellations,  as  Basalt,  Amygda- 
loid, Dolorite,  Greenstone,  and  others. 
The  term  is  meant  to  denote  that  the 
rocks  of  this  class  sometimes  occur  in 
large  tabular  masses,  which  rise  one 
above  another,  like  steps  or  stairs. 

Trap  conglomerate.  The  name  given 
to  conglomerates  formed  of  fragments 
of  greenstone,  basalt,  or  claystone,  to- 
gether with  portions  of  stratified  rocks, 
more  or  less  rounded  by  attrition,  and 
imbedded  in  a  paste  of  the  same  nature, 
or  having  their  intervals  filled  up  by  it. 
Such  deposits,  usually  in  the  form  of 
irregular  beds,  are  named  by  many  geolo- 
gists trap  tufa.    A  considerable  portion 


TRA 


TRI 


of  Arthur's  seat,  near  Edinburgh,  is 
composed  of  this  rock. 

TRAPE'ZIUM  (tpaneCiov,  a  little 
table).  A  term  applied  to  any  quadri- 
lateral figure  which  is  not  a  parallelo- 
gram ;  it  is  therefore  inapplicable  to  the 
square,  the  oblong,  the  rhombus,  and 
the  rhomboid.  Some  writers  apply  the 
term  trapezoid  to  a  quadrilateral,  which 
has  only  two  sides  parallel;  and  trape- 
zium to  a  quadrilateral  having  two  sides 
parallel  and  the  other  two  equal,  but  not 
parallel.  It  has  been  proposed  that  trape- 
zium should  be  the  general  word  for 
plane  quadrilateral  figures,  parallelo 
grams  included  ;  and  that  trapezoid 
should  denote  a  quadrilateral  figure 
whose  sides  are  not  in  the  same  plane. 

TRASS.  A  deposit  of  volcanic  ashes 
and  scoriae  ejected  from  the  Eifel  volca- 
noes, and  accumulated  in  valleys  and  old 
lakes  under  the  influence  of  water.  It 
is  equivalent,  or  nearly  so,  to  the  puz- 
zolana  of  the  Neapolitans. 

TRAUBEN-ERTZ.  The  massive  bo- 
tryoidal  variety  of  green  lead  ore,  one  of 
the  divisions  of  phosphate  of  lead  or 
pyromorphite. 

TRAUMATE.  The  name  given  by 
the  French  geologists  to  graywack6. 

TRAVERSE.  Traverse-sailing,  or  the 
working  of  a  traverse,  is  the  method  of 
calculating  a  ship's  place  after  she  has 
made  two  or  more  short  courses  on  dif- 
ferent points  of  the  compass. 

TRAVERSE  TABLE.  A  table  used 
in  traverse-sailing  and  for  other  pur- 
poses. It  is  a  neat  trigonometrical 
canon,  as  follows  :— The  angle  a  ship 
makes  with  the  meridian  is  the  angle  of 
the  course ;  the  distance  run  in  that 
course  is  the  hypotenuse  of  a  right-angled 
triangle,  and  the  side  opposite  to  the 
angle  of  the  course  is  called  the  depar- 
ture (from  the  meridian).  The  side  ad- 
jacent to  the  angle  of  the  course  is  called 
the  difference  of  latitude  (this  being  found 
from  it  by  reducing  miles  or  leagues  to 
degrees).  The  traverse  table  is  a  table 
of  double  entry,  into  which,  going  with 
the  angle  of  the  course  and  the  distance 
run,  we  find  in  two  columns  the  cor- 
responding departure,  and  length  of  the 
side,  called  difference  of  latitude. — Pen. 
Cycl. 

TRAVERTIN.  The  Italian  term  for 
a  white  concretionary  limestone,  usually 
hard  and  semi-crystalline,  deposited  from 
the  water  of  springs  holding  lime  in  solu- 
tion. The  term  is  not  exactly  equivalent 
to  tufa,  which  expresses  the  loose  and 
343 


porous  surface  deposit  from  calcareous 
springs,  while  travertin  denotes  the  more 
solid  limestone,  less  frequently  formed 
in  lakes  and  on  hill  sides.  This  stone 
was  called  by  the  ancients  Lapis  Tibur- 
tinus,  being  found  in  great  quantity  by 
the  river  Anio,  at  Tibur,  near  Rome. 
Some  suppose  travertin  to  be  an  abbrevia- 
tion of  trasteverino  from  transtiburtinus. 

TREBLE.  In  Music,  the  highest  part 
in  a  concerted  piece.  It  is  distinguished 
into  the  first  or  highest,  and  the  second 
or  low  treble.  Half-treble,  or  mezzo 
soprano,  is  a  high  counter-tenor. 

TREMATO'DA  (rphi^a,  a  hole).  An 
order  of  sterelminthans,  a  parenchy- 
matous entozoa,  furnished  with  organs 
of  imbibition  and  adhesion  in  the  form 
of  suckers. 

TRE'MOLITE.  A  sub-species  of 
straight-edged  augite,  named  from  Val 
Tremola,  where,  however,  it  is  not  found. 
It  is  distinguished  into  the  asbestous, 
the  common,  and  the  glassy  varieties. 

TRIAD,  HARMONIC.  In  Music,  a 
combination  of  three  sounds  which  is 
naturally  divisible  into  two-thirds,  one 
major,  the  other  minor,  constituting  a 
fifth  in  the  whole.  Its  name  is  derived 
from  its  being  formed  of  a  third  and  a 
fifth,  which,  with  the  base  or  funda- 
mental sound,  make  three  different 
terms. 

TRIADE'LPHOUS  (rpetc,  three,  £de\- 
(pia,  brotherhood).  A  term  applied  in 
Botany  to  the  filaments  of  plants  which 
are  combined  into  three  masses,  or  bro- 
therhoods, as  in  some  species  of  hype- 
ricum.     See  Adelphia. 

TRIAKE'NIUM.  The  botanical  de- 
signation of  a  fruit  which  consists  of 
three  achaenia,  or  cells.    See  Achcenium. 

TRIA'NDRIA  (Tpetf,  three,  uvrjp,  a 
man).  The  third  class  of  plants  in  the 
system  of  Linnaeus,  comprising  those 
which  have  three  stamens. 

TRFANGLE  (tres  angulos  habens).  A 
three-sided  figure,  having  necessarily 
three  corners  or  angles.  When  the  lines 
forming  the  sides  are  straight,  the  figure, 
being  on  a  plane,  is  called  a  plane  tri- 
angle ;  when  they  are  curved,  lying  on 
the  surface  of  a  sphere,  the  figure  is  a 
spherical  triangle.  A  triangle  is  equi- 
lateral, when  its  three  sides  are  equal ; 
isosceles,  when  only  two  sides  are  equal ; 
scalene,  when  all  its  sides  are  unequal ; 
right-angled,  when  it  has  a  right  angle ; 
obtuse-angled,  when  it  has  an  obtuse 
angle ;  acute-angled,  when  it  has  three 
acute  angles. 

Q4 


TRI 


TRI 


Triangle  spherical.  A  figure  drawn 
upon  the  superficies  of  a  sphere,  com- 
prehended by  three  arcs  of  three  great 
circles,  each  of  which  is  less  than  a 
semicircle.  In  any  right-angled  spherical 
triangle,  the  complement  of  the  hypo- 
tenuse, the  complements  of  the  angles, 
and  the  two  sides,  are  called  the  circular 
parts  of  the  triangle,  as  if  they  were  fol- 
lowing each  other  in  a  circular  order, 
from  whatever  part  we  begin.  Thus,  if 
any  three  of  these  five  be  taken,  they 
either  will  be  all  contiguous  or  adjacent, 
or  one  of  them  will  not  be  contiguous  to 
either  of  the  other  two :  in  the  first  case, 
the  part  which  is  between  the  other  two 
is  called  the  middle  part,  and  the  other 
two  are  called  adjacent  extremes ;  in  the 
second  case,  the  part  which  is  not  con- 
tiguous to  either  of  the  other  two  is 
called  the  middle  part,  and  the  other  two 
opposite  extremes. 

TRIANGLE,  ARITHMETICAL.  A 
table  of  certain  numbers  disposed  in  the 
form  of  a  triangle.  The  first  column 
contains  units  only;  the  second,  the 
series  of  consecutive  numbers ;  the  third, 
the  series  of  triangular  numbers;  the 
fourth,  the  series  of  pyramidal  numbers ; 
and  so  on  (See  Number).  The  columns 
maybe  continued  vertically  to  any  ex- 
tent— 


1 

1 

1 

1 

2 

1 

1 

3 

3 

1 

1 

4 

6 

4 

1 

1 

5 

10 

10 

5     1 

1 

G 

15 

20 

15     6     1 

Any  number  in  the  table  is  obtained  by 
adding  the  number  immediately  above  it 
in  the  same  column,  to  the  number  in 
same  horizontal  line  in  the  next  preced- 
ing column ;  further,  it  will  be  found 
that  the  oblique  diagonal  rows,  beginning 
from  the  left  side,  are  the  same  as  the 
vertical  columns.  One  of  the  properties 
of  the  table  is,  that  numbers  taken  on 
the  horizontal  lines,  are  the  co-efiicients 
of  the  different  powers  of  a  binomial. 

TRIANGLE  OF  FORCES.  The 
"Parallelogram  of  Forces"  (See  Force) 
may  be  stated  under  another  form, 
termed  the  triangle  of  forces ;  for  it  is 
the  same  thing  whether  we  say  of  three 
straight  lines  that  they  are  the  sides  and 
diagonal  of  a  parallelogram,  or  that  they 
will  form  a  triangle ;  hence  we  may 
assert,  that  forces  will  be  in  equilibrium 
when  they  are  proportional  to  the  sides 
344 


of  a  triangle  formed  by  drawing  lines 
parallel  to  their  directions. 

TRIANGULAR  COMPASSES.  Com- 
passes having  three  legs,  capable  of 
taking  off  three  points  at  once,  and  used 
in  the  construction  of  maps  and  charts. 
Two  of  the  legs  open  as  in  the  common 
compasses,  while  the  third  turns  round 
an  extension  of  the  central  pin  of  the 
other  two,  besides  having  a  motion  on  its 
own  central  joint. 

TRIANGULAR  NUMBERS.  A  series 
of  numbers  formed  by  the  successive 
sums  of  the  terms  of  an  arithmetical  pro- 
gression, of  which  the  common  difference 
is  1.    Thus— 

Arith.  Progression     1,  2,  3,  4,  5,  6,  &c. 
Triangular  Numbers  1,  3,  6,  10, 15, 21,  &c. 

The  general  formula  for  the  series 
is  £  n  (n  +  1 ).     See  Number. 

TRI  ANGULATION.  A  name  given 
to  the  net-work  of  triangles  with  which 
the  face  of  a  country  is  covered  in  a 
trigonometrical  survey. 

TRIA'NGULUM.  The  triangle;  a 
northern  constellation,  consisting  of  six- 
teen stars,  surrounded  by  Perseus,  An- 
dromeda, Aries,  and  Musca.  The  tri- 
angulum  australe  is  a  modern  southern 
constellation,  consisting  of  five  stars, 
lying  between  Ara,  Centaurus,  and  the 
South  Pole. 

TRIA'SSIC  SYSTEM.  New  red  sand- 
stone and  saliferous  marls.  A  geological 
system,  forming  the  base  of  the  great 
central  plains  of  England,  and  sur- 
mounted by  the  saliferous  marls  and  red 
arenaceous  beds  which  pass  under  the 
great  oolitic  terrace,  or  rather  the  succes- 
sion of  terraces  which  stretch  across 
England  from  the  coast  of  Devonshire  to 
the  north-eastern  coast  of  Yorkshire. 

TRIBA'SIC  SALTS.  The  name  given 
to  a  class  of  oxygen-acid  salts,  which,  in 
the  language  of  the  old  theory,  contain 
three  atoms  of  base  to  one  of  acid,  and 
of  which  the  tribasic  phosphates  are  the 
type. 

TRICA.  Gyroma.  In  the  botanical 
nomenclature  of  lichens,  this  term  de- 
notes a  shield,  the  surface  of  which  is 
covered  with  sinuous  concentric  furrows. 

TRICHI'DIUM  (rpixtiiov,  from  0P<f, 
a  hair).  Pecten.  A  botanical  term  for 
a  tender,  simple,  or  sometimes  branched 
hair,  which  supports  the  sporules  of  some 
fungaceous  plants,  as  geastrum. 

TRICHO'PTERA  (0Pif,  rpixbs,  hair, 
mepov,  a  wing).  An  order  of  insects, 
distinguished  by  the  hairy  covering  of 
their  wings  and  bodies.    Their  larvae  are 


TRI 


TRI 


well  known  under  the  name  of  caddice- 
worms. 

TRICHO'TOMOUS  {rpiXa,  in  three 
parts,  re/ui/to,  to  cut).  A  designation  of 
the  mode  of  branching  or  of  inflores- 
cence, when  the  divisions  occur  in  threes, 
as  in  the  stem  of  Marvel  of  Peru. 

TRIDACNI'DjE.  The  name  given  by 
Lamarck  to  a  family  belonging  to  the  first 
section  of  his  monomyarian  conchifers, 
or  mollusks  furnished  with  bivalve  shells 
which  have  a  single  muscular  impres- 
sion. This  family  comprises  the  genera 
tridacna  and  hippopus. 

TRIFID,  TRISECTED,  TRIPART- 
ED,  &c.  These  and  other  terms  are 
applied  by  botanists  to  the  forms  of 
leaves,  with  especial  reference  to  the 
number  and  the  depth  of  their  lobes,  ac- 
cording as  they  have,  respectively,  fis- 
sures, segments,  or  partitions.  And,  on 
the  other  hand,  we  may,  by  neglecting  the 
number  of  the  lobes,  simply  indicate 
their  presence  by  saying  that  a  leaf  is 
pinnatilobed,  palmatilobed,  and  so  on. 
The  lobes  themselves  are  sometimes  sub- 
divided upon  the  same  principle  as  the 
leaf  itself :  thus  we  say  that  a  leaf  is  tri- 
pinnatisected,  tripinnatiparted,  tripin- 
natifid,  when  the  subdivisions  of  the  lobes 
are  themselves  lobed. 

TRFGLIDjE.  The  Gurnard  tribe  of 
acanthopterygious  or  spiny-finned  fishes, 
generally  resembling  the  Percidae,  but 
having  their  head  armed  with  spines  or 
hard  scaly  plates. 

TRIGO'NIDjE  (tp/ywi/o?,  triangular). 
A  family  of  conchiferous  mollusks,  named 
from  the  genus  trigonia,  the  shell  of 
which  is  of  a  subtrigonal  form. 

TRIGONO'METRY  {jpi^avov,  a  tri- 
angle, jueTpea>,  to  measure).  This  term 
originally  denoted  simply  the  science  by 
which  those  relations  are  determined 
which  the  sides  and  angles  of  a  triangle 
have  to  each  other,  being  called  plane  or 
spherical  trigonometry,  according  as  the 
triangle  was  described  on  a  plane  or  a 
spherical  surface.  By  means  of  certain 
proportions  always  holding  good  between 
the  three  sides  and  the  three  angles  of  a 
triangle,  we  are  enabled,  by  the  aid  of 
this  branch  of  mathematics,  when  any 
three  of  these  six  quantities  are  known 
(provided  that  one  of  these  known  quan- 
tities be  a  side),  to  find  the  other  three. 
At  present,  the  term  has  a  much  more 
extensive  meaning,  as  the  science  now 
embraces  all  the  theorems  expressing  the 
relations  between  angles  and  certain 
functions  of  them ;  it  embraces  the 
345 


consideration  of  alternating  and  pe- 
riodic magnitude  ;  in  which  quantity 
is  imagined  to  go  through  alterations 
of  increase  and  diminution  without 
end. 

1.  Definitions  of  Trigonometrical  Lines. 

1 .  The  complement  of  an  arc  is  its  differ- 
ence from  a  quadrant;  and  that  of  an 
angle,  its  difference  from  a  right  angle. 

2.  The  supplement  of  an  arc  is  its  defect 
from  a  semicircle  ;  and  that  of  an  angle, 
its  defect  from  two  right  angles.  3.  The 
sine  of  an  arc  is  a  line  drawn  from  one  of 
its  extremities,  perpendicular  to  the  ra- 
dius passing  through  its  other  extre- 
mity. 4.  The  tangent  of  an  arc  is  a  line 
touching  it  at  one  extremity,  and  limited 
by  the  radius  produced  through  its  other 
extremity.  5.  The  secant  of  an  arc  is 
that  portion  of  the  radius  produced, 
which  is  intercepted  between  the  extre- 
mity of  the  tangent  and  the  centre. 
6.  The  versed  sine  of  an  arc  is  that  por- 
tion of  the  radius  intercepted  between 
the  sine  and  the  extremity  of  the 
arc.  7.  The  supplemental  versed  sine, 
or  suversed  sine  is  the  difference  be- 
tween the  versed  sine  and  the  dia- 
meter. 8.  The  sine,  tangent,  &c.  of  the 
complement  of  an  arc,  are  concisely 
termed  the  cosine,  cotangent,  &c.  of  that 
arc.  These  terms,  for  conciseness,  are 
usually  contracted  into  sin.,  tan.,  sec, 
vers.,  suvers,  cos.,  cot.,  cosec,  covers., 
and  cosuvers. 

2.  Trigonometrical  Functions  of  an 
Angle.  1.  The  ratio  which  the  sine  ot 
an  angle  bears  to  its  cosine  is  called  the 
tangent  of  the  angle.  2.  The  inverse  of 
this  ratio  is  called  the  cotangent.  3.  The 
ratio  of  unity  to  the  cosine  of  an  angle  is 
denominated  the  secant ;  and  that  of 
unity  to  the  sine,  the  cosecant.  4.  The 
difference  between  unity  and  the  cosine 
is  called  the  versed  sine.  5.  The  differ- 
ence between  unity  and  the  sine  of  an 
angle  is  called  the  coversed  sine.  These 
are  functions  of  the  angle,  and  are  quite 
independent  of  the  absolute  length  of  the 
arc  subtending  it,  or  of  the  radius  of  that 
arc. 

3.  Signs  of  the  trigonometrical  lines. 
The  signs  +  and  -,  which  in  arithmetic 
indicate  addition  and  subtraction,  are 
used  in  geometry  to  point  out  opposition 
in  direction.  Quantities  whose  signs  are 
+  ,  are  called  positive,  and  those  whose 
signs  are  — ,  are  called  negative.  If  a 
line  be  measured  from  a  given  point  or  a 
given  line  as  its  origin,  it  is  reckoned 

|  positive  when  it  lies  on  one  side  of  its 
Q5 


TRI 


TRI 


origin,  and  negative  when  on  the  opposite 
side. 

4.  Trigonometrical  Tables.  There  are 
two  kinds  of  trigonometrical  tables.  The 
first  kind  contains  the  sines,  cosines,  &c. 
of  angles,  calculated  to  the  radius  unity ; 
the  sines,  cosines,  tangents,  and  secants 
in  these  tables  to  radius  1,  are  called 
natural,  to  distinguish  them  from  those 
of  the  second  kind,  which  are  called  arti- 
ficial or  logarithmic.  By  aid  of  the  latter 
tables,  instead  of  multiplying  natural 
sines,  &c,  we  need  only  add  the  loga- 
rithmic sines,  &c. ;  and,  instead  of  di- 
viding a  natural  sine  or  cosine,  &c.  by 
another,  we  need  only  subtract  the  loga- 
rithmic sine,  &c,  which  represents  the 
dividend.  By  these  operations  much 
time  and  labour  are  saved. 

5.  Trigonometrical  Canon.  This  is  a 
table,  which,  beginning  from  one  second 
or  one  minute,  orderly  expresses  the 
lengths  which  every  sign,  tangent,  and 
secant  have,  in  respect  of  the  radius, 
which  is  supposed  unity;  and  is  con- 
ceived to  be  divided  into  10,000,000  or 
more  decimal  parts.  And  so  the  sine, 
tangent,  or  secant  of  an  arc,  may  be  had 
by  the  help  of  this  table ;  and,  contrari- 
wise, a  sine,  tangent,  or  secant  being 
given,  we  may  find  the  arc  it  expresses. 

6.  Trigonometrical  Curves  and  Series. 
The  former  are  curves  having  such  equa- 
tions as  y  =  sin  x,  y  =  cos  x,  y  =  a  cos 
x  +  b  cos  2x,  &c.  The  latter  are  infinite 
series  of  the  form  a  sin  x  +  b  sin  2x  +  c 
sin  3a:  +  &c,  and  a  cos  x  +  b  cos  2x  +  c 
cos  3a;  +  &c. 

7.  Trigonometrical  Survey.  The  appli- 
cation of  trigonometry  to  geodetic  opera- 
tions, for  topographical  purposes,  and 
for  measurements  connected  with  gene- 
ral geography  and  with  the  figure  of  the 
earth. 

TRIGY'NIA  (rpelf,  three,  yvvt],  a 
woman).  The  name  given  by  Linnaeus 
to  those  orders  of  plants  which  have 
three  pistils. 

TRILLION.  A  million  of  billions,  or  a 
million  of  million  of  millions. 

TRFLOBITE  (rpel?,  three,  \o/36?,  a 
lobe).  An  extinct  crustacean  animal,  al- 
most the  sole  representative  of  its  class 
in  the  periods  which  intervened  between 
the  deposition  of  the  earliest  fossiliferous 
strata  and  the  end  of  the  coal  formation. 
It  if  named  from  the  upper  surface  of 
its  body  being  divided  into  three  lobes. 

TRFMERA  (Tpelc,  three,  nepos,  a 
part).  A  section  of  coleopterous  insects, 
in  which  only  three  ordinary- sized  joints 
346 


exist  in  the  tarsi,  the  fourth  being  mi- 
nute and  indistinct.    Latreille. 

TRIMYA'RIANS  (Tpelr,  three,  Muc,  a 
muscle).  A  designation  of  those  bi- 
valves which  present  three  muscular  im- 
pressions on  each  valve. 

TRFNGID^E.  A  group  of  birds,  dis- 
tinguished from  all  others  by  the  great 
length,  the  slenderness,  and  the  flex- 
ibility of  the  bill,  no  less  than  by  the 
delicacy  of  the  legs  and  the  smallness  of 
the  hinder  toe.  The  tringa,  or  sand- 
piper, is  the  type  of  the  group.  They 
belong  to  the  family  Scolopacidae. 

TRINO'MIAL.  An  algebraical  name 
for  an  expression  consisting  of  three 
terms,  as  a  +  b  +  c,  or  ax  —  bx3  +  bx4. 

TRIPHANE.  Spodumene.  A  silicate 
of  lithia  and  alumina,  first  discovered  in 
the  island  of  Uton  in  Sudermannland, 
where  it  is  associated  with  red  felspar 
and  quartz,  and  lately  by  Dr.  Taylor  in 
the  vicinity  of  Dublin. 

TRIPHYLINE.  A  phosphate  of  iron, 
manganese,  and  lithia. 

TRIPI'NNATE  ;  TRITE'RNATE. 
1.  The  former  of  these  terms  is  applied 
by  botanical  writers  to  a  leaf  in  which 
there  are  three  series  of  pinnation,  as 
when  the  leaflets  of  a  bipinnate  leaf  are 
themselves  pinnate.  2.  The  latter  term 
denotes  a  leaf  in  which  there  are  three 
series  of  ternation,  as  when  the  leaflets  of 
a  biternate  leaf  are  themselves  ternate. 

TRIPLE  SALTS.  A  term  sometimes 
applied,  in  chemistry,  to  salts  in  which 
two  bases  are  combined  with  one  acid,  as 
soda  and  potassa  with  tartaric  acid  in 
Rochelle  salt.  These  compounds  are, 
however,  more  commonly  viewed  as 
double  salts,  Rochelle  salt  being  consi- 
dered as  composed  of  single  equivalents 
of  the  tartrates  of  soda  and  potassa. 

TRPPLICATE  RATIO.  The  compo- 
sition of  a  ratio  with  itself  twice :  thus 
the  ratio  of  a3  to  b3  is  the  triplicate  of 
the  ratio  of  a  to  b.  In  other  words,  the 
triplicate  of  a  given  ratio  is  found  by 
taking  the  cube  of  each  of  the  terms  of 
the  ratio.  Thus,  when  it  is  said  that 
two  similar  solids,  whose  linear  dimen- 
sions are  as  6  to  9,  are  in  the  triplicate 
ratio  of  6  to  9,  it  is  meant  that  the  con- 
tents of  these  solids  are  in  the  ratio  of 
6  x  6  x  6  to  9  x  9  x  9,  or  216  to  729. 

TRIPLITE.  Phosphate  of  manga- 
nese, found  at  Chanteloube,  near  Li- 
moges, in  the  department  of  Haute 
Vienne  in  France,  where  several  other 
mineral  substances  have  lately  been 
found,  the  essential  constituents  of  which 


TRO 


TRO 


are  iron,  manganese,  and  phosphoric 
acid. 

TRPPOLI.  A  powder  used  for  polish- 
ing metals  and  stones,  first  imported 
from  Tripoli,  which,  as  well  as  a  certain 
kind  of  siliceous  stone  of  the  same  name, 
has  been  lately  found  to  be  composed  of 
the  flinty  cases  of  infusoria.  It  is  found 
at  Bakewell,  in  Derbyshire,  where  it  is 
called  rotten-stone. 

TRITO'XIDE.  An  oxide  containing 
one  atom  of  base  combined  with  three 
atoms  of  oxygen. 

TRO'CHIDjE.  A  family  of  phyto- 
phagous Gasteropods,  which  have  a  tur- 
binate, mostly  trochiform,  or  top-like 
shell,  the  substance  of  which  is  almost 
always  perlaceous;  the  outer  lip  never 
thickened ;  the  aperture  entire,  closed 
by  a  shelly  or  horny  operculum. 

TROCHI'LIDjE  (trochilus,  a  hum- 
ming-bird). The  Humming-bird  tribe ; 
a  family  of  the  Insessores,  or  Perching- 
birds,  characterized  by  the  brilliancy  of 
their  plumage,  and  by  the  humming 
sound  which  accompanies  their  flight. 
See  Tenuirostres. 

TROCHl'NiE.  Troehuses,  or  Top- 
shells  ;  a  sub-family  of  the  Trochidce, 
named  from  the  genus  trochus ;  the 
shape  of  these  shells  is  pyramidal,  the 
body-whorl  flattened,  and  the  aperture 
closed  by  a  horny  operculum. 

TRO'CHOID  (tpoX6p,  a  wheel,  efeo?, 
likeness).  A  curve  described  by  any 
point  in  a  wheel  as  it  rolls  forward  on  a 
plane.  The  term  is  synonymous  with 
cycloid. 

TROCHOI'DAL  CURVES  {rpoX6t,  a 
•wheel  or  hoop,  elios,  likeness).  "  Under 
this  term  is  included  a  large  number  of 
lines  which  are  produced  by  the  com- 
position of  two  circular  motions,  includ- 
ing the  straight  line,  the  circle,  the  el- 
lipse, a  class  of  curves  called  epitro- 
choids,  of  which  one  particular  case  is 
called  the  epicycloid,  and  a  class  called 
hypotrochoids,  of  which  one  particular 
case  is  the  hypocloid.  Among  these 
must  also  be  included  the  extreme  case 
in  which  one  of  the  motions  is  rectilinear, 
which  gives  the  common  trochoid,  the 
cycloid,  and  a  class  of  spirals  which  in- 
cludes the  involute  of  the  circle,  the 
spiral  of  Archimedes,  and  others." — Pen. 
Cycl. 

Trochoidal  and  Planetary  Motions.  In 
the  trochoidal  motion,  which  is  univer- 
sally adopted,  one  circle  is  made  to  roll 
like  a  hoop,  either  upon  a  straight  line, 
or  upon  the  circumference  of  another 
347 


circle.  The  planetary  motion  resembles 
that  in  which  a  planet  and  its  satellite 
move  round  the  sun.  Here  a  circle, 
without  any  rolling,  has  its  centre  carried 
round  the  circumference  of  another. 

TROGO'NIDjE.  A  family  of  the  In- 
sessores, or  Perching-birds,  remarkable 
for  the  beauty  of  their  plumage,  com- 
prising the  woodpecker,  the  cuckoos,  the 
trogons,  the  toucans,  &c. 

TRONA.  The  name  given  in  Africa 
to  the  sesqui-carbonate  of  soda,  imported 
from  the  coast  of  Barbary,  where  it  is 
collected  by  the  natives. 

TRO'PHI  (rpo<pot,  a  nourisher).  In- 
strumenta  cibaria.  In  insects,  the  organs 
which  form  the  mouth,  consisting  of  an 
upper  and  an  under  lip,  and  comprising 
the  mandibles,  maxillae,  and  palpi,  or 
the  parts  employed  in  acquiring  and  pre- 
paring food. 

TROPHOPOLLEN.  The  name  given 
by  Turpin  to  the  septum  of  the  anther  of 
plants,  from  which  the  pollen  has  been 
incorrectly  supposed  to  separate.  By 
others,  this  part  has  been  termed  the 
receptacle  of  the  pollen,  and  by  Link  the 
raphe. 

TRO'PHOSPERM  (rpe^us,  to  nourish, 
(TirepiMa.,  seed).  The  name  given  by 
Richard  to  the  placenta  in  plants,  the 
part  from  which  the  ovules  arise.  It 
generally  occupies  the  whole  or  a  portion 
of  one  angle  of  each  cell. 

TROPICS  (Tpo7riK6f,  from  rpena,  to 
turn).  Those  two  circles  on  the  earth, 
over  which  the  sun  seems  directly  to 
pass,  when  he  is  at  the  greatest  distance 
from  the  equator  northward  and  south- 
ward (viz.  23£  degrees) ;  hence,  the  one 
is  called  the  Northern,  the  other  the 
Southern  Tropic.  They  correspond  to 
the  sun's  position  at  the  solstices,  and 
are  the  limits  of  the  torrid  zone. 

1.  Tropic  of  Cancer.  A  designation  of 
the  Northern  Tropic,  because,  when  the 
sun  appears  to  move  vertically  over  this 
tropic,  he  appears  to  be  in  the  beginning 
of  Cancer. 

2.  Tropic  of  Capricorn.  A  designation 
of  the  Southern  Tropic,  because,  when 
the  sun  appears  to  move  vertically  over 
this  tropic,  he  appears  to  be  in  the  begin- 
ning of  Capricorn. 

3.  The  term  Tropic  denotes  a  point 
where  a  turn  is  made ;  for  the  line  of  the 
ecliptic  quitting  the  equator  in  the  first 
point  of  Aries,  continues  to  rise  higher 
northward  from  it  till  it  reaches  the  first 
point  of  Cancer,  when  it  turns  to  the 
southward ;  and,  after  again  cutting  the 

Q6 


TRU 


TRU 


equator  at  the  first  point  of  Libra,  con- 
tinues to  descend  southward  till  it 
reaches  the  first  point  of  Capricorn,  when 
it  again  turns  to  the  northward  and 
reaches  Aries. 

TROPICAL  YEAR.  The  period  of 
time  which  intervenes  between  two  coin- 
cidences of  the  sun  with  the  vernal  equi- 
nox. This  is  the  common  or  civil  year, 
in  which  the  phenomena  of  the  seasons 
are  repeated,  and  after  which  they  recom- 
mence. It  depends  chiefly  and  directly 
on  the  annual  revolution  of  the  earth 
round  the  sun,  but  subordinately  also, 
and  indirectly,  on  its  rotation  round  its 
own  axis,  which  occasions  the  precession 
of  the  equinoxes.  It  consists  of  365d. 
5h.  48m.  49s.  7 ;  it  is,  therefore,  shorter 
than  the  sidereal  year,  or  the  period  of 
the  actual  revolution  of  the  earth  round 
the  sun,  by  4'  39".  7.  See  Anomalistic 
Year. 

TROUGH  APPARATUS.  Oersted's 
trough  apparatus  is  essentially  the  same 
as  Wollaston's  battery.  It  consists  of  a 
trough  of  copper  plate,  in  the  form  of  a 
parallelopiped,  about  £  an  inch  wide  at 
the  bottom;  in  it  the  zinc  plates  are 
arranged  so  as  not  to  touch  the  copper ; 
the  trough  serves  also  to  hold  the  liquid. 

TROUGH,  PNEUMATIC.  A  vessel 
made  of  tinned  iron  for  collecting  gases. 
It  has  a  moveable  stage  or  bridge,  above 
which  water  is  to  be  poured  to  the  height 
of  about  an  inch.  The  bridge  is  perfo- 
rated by  a  round  hole,  communicating 
above  with  an  inverted  receiver,  into 
which  it  transmits  the  gas  conveyed  to  it 
by  a  tube  beneath  the  surface  of  the 
water. 

TRUE  PLACE.  In  Astronomy,  the 
place  which  a  star  or  planet  appears  to 
occupy  in  the  heavens  is  not  called  its 
true  place,  but  that  which  it  would  oc- 
cupy if  corrections  were  made  for  paral- 
lax, refraction,  &c. ;  that  is,  if  the  spec- 
tator made  his  observation  from  the  cen- 
tre of  the  earth,  and  without  the  light 
passing  through  a  refracting  medium. 

TRUMPET.  The  speaking  trumpet  is 
an  instrument,  best  when  made  of  a 
parabolic  form,  for  rendering  the  human 
voice  audible  at  a  great  distance.  This 
object  is  accomplished  by  the  rays  of 
sound  being  reflected  from  the  interior 
of  the  trumpet,  as  the  words  are  spoken 
,  at  the  smaller  end,  in  such  a  manner  that 
they  issue  from  the  expanded  mouth 
parallel  to  each  other,  and  consequently 
agitate  the  air  in  the  direction  in  which 
the  axis  of  the  trumpet  is  held,  more 
348 


forcibly  than  they  would  had  they  pro- 
ceeded immediately  from  the  mouth  of 
the  speaker.  The  efficiency  of  this  in- 
strument increases  with  its  length  :  a 
strong  man's  voice,  sent  through  a  trum- 
pet from  18  to  24  feet  in  length,  may  be 
heard  at  a  distance  of  3  miles. 

The  hearing  trumpet  inverts  the  opera- 
tion above  described,  the  rays  of  sound 
being  received  at  the  large  opening,  and 
reflected  so  as  to  become  united  at  the 
small  aperture  which  is  inserted  into  the 
ear. 

TRUNK;  STEM;  &c.  The  former 
term  is  applied  by  botanists  to  the  main 
stem  of  trees ;  while  the  latter  is  gene- 
rally used  to  denote  the  ascending  axis  of 
herbaceous  plants  or  shrubs,  but  not  of 
trees.  The  culm  or  straw  is  the  stem  of 
grasses ;  to  these  terms  De  Candolle  adds 
calamus,  applying  it  to  all  fistular  simple 
stems  without  articulations,  as  those  of 
rushes. 

TRUTH.  This  term,  in  its  strict  logi- 
cal sense,  applies  to  propositions  and 
to  nothing  else;  and  consists  in  the  con- 
formity of  the  declaration  made  to  the 
actual  state  of  the  case ;  agreeably  to 
Aldrich's  definition  of  a  "true"  propo- 
sition— vera  est,  quae  quod  res  est  dicit. 
It  would  be  an  advantage,  observes 
Whately,  if  the  word  Trueness  or  Verity 
could  be  introduced  and  employed  in 
this  sense,  since  the  word  Truth  is  so 
often  used  to  denote  the  "  true "  pro- 
position itself.  "  What  I  tell  you  is  the 
Truth ;  the  Truth  of  what  I  say  shall  be 
proved :"  the  term  is  here  used  in  these 
two  senses. 

1.  Truth,  in  its  etymological  sense, 
signifies  that  which  the  speaker  "  trows," 
or  believes  to  be  the  fact.  The  etymology 
of  the  word  aXrj0er  seems  to  be  similar, 
denoting  non-concealment.  In  this  sense 
it  is  opposed  to  a  lie ;  and  may  be  called 
moral,  as  the  other  may  logical,  truth. 
A  witness  therefore  may  comply  with 
his  oath  to  speak  the  truth,  though  it  so 
happen  that  he  is  mistaken  in  some  par- 
ticular of  his  evidence,  provided  he  is 
fully  convinced  that  the  thing  is  as  he 
states  it. 

2.  Truth  is  not  unfrequently  applied, 
in  loose  and  inaccurate  language,  to 
arguments  ;  where  the  proper  expression 
would  be  "Correctness,"  '* conclusive- 
ness," or  "validity." 

3.  Truth,  again,  is  often  used  in  the 
sense  of  Reality,  r6  ov.  Persons  speak 
of  the  truth  or  falsity  of  facts ;  properly 
speaking,   they  are   either   real  or  fie- 


TUB 


TUN 


titious :  it  is  the  statement  that  is  either 
"true"  or  "false."  The  "true"  cause 
of  any  thing,  is  a  common  expression  ; 
meaning  **  that  which  may  with  truth 
he  assigned  as  the  cause."  The  senses 
of  falsehood  correspond.     Whately. 

TRYMA.  The  botanical  designation 
of  a  syncarpous  fruit,  which  is  superior, 
by  abortion  one-celled,  one- seeded,  with 
a  two-valved  indehiscent  endocarp,  and 
a  coriaceous  or  fleshy  valveless  sarco- 
carp,  as  in  walnut. 

TUBE.  The  surface  of  a  tube  is  gene- 
rally a  cylinder,  but  this  word  may  be 
made  use  of  in  mathematics.  When  a 
tube  is  bent,  there  is  no  distinct  geome- 
trical name  for  it,  but  the  following  defi- 
nition might  do  very  well  :  let  a  surface 
be  called  a  tube  when  it  is  formed  by  a 
circle  which  moves  with  its  centre  upon 
a  given  curve,  and  its  plane  always  per- 
pendicular to  the  tangent  of  that  curve. 
This  would  include  the  straight  tube,  or 
common  circular  cylinder,  and  every 
species  of  bent  tube. — Pen.  Cycl. 

TUBE  OF  SAFETY.  A  tube  open 
at  both  ends,  inserted  into  a  receiver,  the 
upper  end  communicating  with  the  ex- 
ternal air,  and  the  lower  being  immersed 
in  water.  Its  intention  is  to  prevent 
injury  from  too  sudden  condensation  or 
rarefaction  taking  place  during  chemical 
operations ;  for,  if  a  vacuum  be  produced 
within  the  vessels,  the  external  air  will 
enter  through  the  tube  ;  and  if  air  be 
generated,  the  water  will  yield  to  the 
pressure,  being  forced  up  the  tube. 
Thus,  too,  the  height  of  the  water  in  the 
tube  indicates  the  degree  of  pressure 
from  the  confined  gas  or  gases. 

TUBER.  An  annual  thickened  sub- 
terranean stem,  provided  at  the  sides 
with  latent  buds,  from  which  new  plants 
are  produced,  as  in  the  potato.  When 
very  small  it  is  called  tubercle. 

TUBFCOLjE  (tubus,  a  tube,  colo,  to 
inhabit).  An  order  of  Annellida,  or  red- 
blooded  worms,  enclosed  in  an  elongated 
tube,  which  is  formed  either  by  the  ag- 
glutination of  foreign  matters,  or  by  the 
secretion  of  calcareous  matter  resembling 
that  of  the  shells  of  certain  bivalves. 
These  are  the  Pinceaux  de  Mer  of  the 
French. 

The  term  Tubicola  also  denotes  a 
family  of  Spiders,  which  enclose  them- 
selves in  a  silken  tube,  strengthened  ex- 
ternally by  leaves  or  other  foreign  sub- 
stances. 

TU'BICORNS  {tubus,  a  tube,  cornu, 
a  horn).  A  family  of  the  Ruminantia,  in 
349 


which  the  horns  are  composed  of  a  horny 
axis  covered  with  a  horny  sheath. 

TUBIPO'RIDjE  {tubus,  a  tube,  porus, 
a  pore).  A  class  of  polyps,  enclosed  in  a 
calcareous  or  coriaceous  sheath  or  tube, 
from  the  orifice  of  which  the  polyp  is 
protruded  when  in  search  of  prey.  These 
are  called  vaginated-polyps. 

TUBFPORITES.  The  name  given  to 
the  fossil  species  supposed  to  belong  to 
tnbipora. 

TU'BIVALVES  (tubus,  a  tube,  valvcc, 
folding-doors).  Tubicolidce.  A  desig- 
nation of  those  bivalves  which  are  fur- 
nished with  a  testaceous  tube,  as  teredo. 
The  animals  of  this  family  are  borers, 
burrowing  in  stone,  wood,  and  even  in 
thick  shell ;  but  some,  nevertheless,  live 
in  the  sand. 

TU'BULATURE  (tubulus,  a  little 
tube).  The  mouth,  or  short  neck,  at  the 
upper  part  of  a  tubulated  retort.  The 
long  neck  is  called  the  beak. 

TU'BULIBRANCHIA'TA  (tubulus,  a 
little  tube,  branchice,  gills).  An  order  of 
gasteropods,  the  shells  of  which  consist 
of  long  and  irregular  tubes  usually  fixed 
to  foreign  bodies,  but  having  the  earliest 
formed  portion  twisted  into  a  few  spiral 
curves,  as  in  vermetus. 

TU'BULIPO'RIM:.  A  family  of  the 
Polypiaria  solida  of  Blainville,  who  de- 
scribes them,  as  animals  contained  in 
cells  of  a  tubular  figure,  with  a  round 
mouth,  which  are  accumulated  irregu- 
larly, so  as  to  form  an  attached  solid 
polyparium.  The  animals  are  known 
only  in  the  genus  tubulipora 

TUFA,  or  TUFF,  VOLCANIC.  A 
variety  of  volcanic  rock,  of  an  earthy 
texture,  seldom  very  compact,  composed 
of  agglutinated  fragments  of  scoriae  and 
loose  materials  ejected  from  volcanoes. 

1.  Tufa,  calcareous.  A  porous  rock 
deposited  by  calcareous  waters  on  their 
exposure  to  the  air,  and  usually  contain- 
ing portions  of  plants  and  other  organic 
substances  incrusted  with  carbonate  of 
lime.  The  more  solid  form  of  the  same 
deposit  is  called  travertin,  into  which  it 
passes. 

2.  Tufa,  trachytic.  Beds  and  irregular 
deposits  of  conglomerate,  composed  of 
fragments  of  trachyte  and  other  volcanic 
substances,  are  often  abundant  in  vol- 
canic districts.  When  reduced  to  the 
state  of  sand  or  powder,  they  form  beds 
of  tufa,  analogous  to  those  of  the  trap 
series. 

TUNGSTEN.  A  Swedish  term,  sig* 
nifying  heavy  stone,  and  applied  to  an 


TUR 


TUR 


element  which  exists  in  the  form  of 
tungstic  acid  in  several  minerals,  the 
most  important  of  which  are  the  native 
tungstate  of  lime,  also  called  scheelite ; 
and  the  tungstate  of  manganese  and 
iron,  also  called  wolfram.  The  tung- 
state of  lead,  or  scheel-lead  ore,  was 
formerly  confounded  with  the  molybdate 
of  this  metal. 

TUNICA'TA  {tunica,  a  tunic).  The 
first  class  of  the  mollusca,  comprising 
soft,  aquatic,  acephalous  animals,  having 
their  body  enveloped  in  an  elastic  tunic, 
furnished  with  at  least  two  apertures. 
They  are  distinguished  into  two  orders, 
viz.  the  Salparia,  in  which  the  forms  are 
organically  united ;  and  the  Ascidiaria, 
which  continue  isolated  by  their  external 
tunic. 

TUPAFADjE.  The  Bangsrings ;  a 
family  of  insectivorous  vertebrate  ani- 
mals, consisting  of  the  single  genus 
tupaia.  They  are  confined  to  the  Indian 
Archipelago,  where,  contrary  to  the  usual 
habits  of  the  insectivora,  they  live  in 
trees,  which  they  ascend  with  the  agility 
of  quadrumanous  animals. 

TU'RBIDjE.  Marine  snails ;  a  family 
of  phytophagous  gasteropods,  which 
breathe  by  gills,  and  often  exhibit  the 
carnivorous  structure  of  the  zoophagous 
division  of  gasteropods.  The  shell  is 
solid,  but  not  perlaceous,  spiral ;  the 
aperture  entire,  closed  by  an  operculum. 

TURBI'NjE.  Winkles;  a  sub-family 
of  the  Turbidce,  named  from  the  typical 
genus  turbo ;  these  are  all  marine  shells, 
with  a  perfectly  entire  aperture. 

TURBINATED  (turbo,  a  top).  A 
term  applied  to  shells  which  have  a  spi- 
ral or  screw-form  structure,  as  that  of 
the  garden-snail. 

TURBINE'LLIDiE.  Turnip-shells ;  a 
family  of  carnivorous  gasteropods,  in 
which  the  base  of  the  shell  is  straight 
and  lengthened,  and  the  pillar  strongly 
plaited.  The  mantle  of  the  animal  is 
never  dilated,  but  is  of  ordinary  dimen- 
sions, and  drawn  back  into  the  shell  with 
the  animal. 

TURBINELLI'NiE.  A  sub-family  of 
the  Turbinellidce,  or  Turnip-shells, 
named  from  the  typical  genus  turbinella, 
and  characterized  by  the  great  size, 
weight,  and  smoothness  of  the  shell,  the 
great  length  of  the  canal,  and  the  gene- 
rally papillary  state  of  the  spire. 

TURBI'NIDjE.      A    family    of    gas- 

tropodous    mollusks,    named    from   the 

genus  turbo.      According  to    Linnaeus, 

the  animal  is  a  limax  or  slug ;  the  shell 

350 


is  univalve,  spiral,  solid;  the  aperture 
narrowed,  orbiculate,  entire.  Lamarck 
gives  the  name  Turbinacea  to  the  last 
family  of  his  herbivorous  trachelipods ; 
all  are  marine  shells,  appearing  to  be 
provided  with  an  operculum. 

TURDI'NjE  (turdus,  a  thrush).  Tur- 
dine  birds  or  thrushes ;  a  family  of  the 
Cantatrices  of  Macgillivray,  which  have 
a  moderately  rapid,  somewhat  undulated 
flight,  and  on  the  ground  advance  by 
leaping.  Most  of  the  species  are  re- 
markable for  their  superiority  of  song. 

TURIO.  The  botanical  term  for  a 
scaly  bud,  developed  from  a  perennial 
subterranean  root,  as  in  asparagus. 

TURKEY-SLATE.  Whet-slate;  No- 
vaculite.  A  massive  greenish-grey  mi- 
neral, occurring  in  beds  in  primitive  and 
transition  clay-slate.  Very  fine  varieties 
are  brought  from  Turkey,  called  hone- 
stones.  It  is  used  for  sharpening  steel 
instruments. 

TURMERIC.  The  tuber  of  the  cur- 
cuma longa,  which  yields  a  beautiful 
bright  yellow  colour.  Turmeric  paper  is 
unsized  paper,  brushed  over  with  tincture 
of  turmeric,  prepared  by  digesting  one 
part  of  bruised  turmeric  in  six  parts  of 
proof  spirit. 

TURNBULL'S  BLUE.  Ferricyanide 
of  iron.  A  blue  precipitate  which  is 
thrown  down  when  red  prussiate  of  pot- 
ash is  added  to  a  protosalt  of  tin. 

TU'RNERITE.  A  rare  mineral,  con- 
taining alumina,  lime,  magnesia,  and  iron, 
found  only  on  Mount  Sorel  in  Dauphiny. 

TURNER'S  YELLOW.  Cassel  Yel- 
low; Patent  Yellow.  An  oxichloride  of 
lead. 

TURNSOLE.  A  deep  purple  dye  ob- 
tained from  the  crozophora  tinctoria,  an 
euphorbiaceous  plant. 

TURPETH  MINERAL.  The  name 
given  by  chemists  to  the  sub-sulphate  of 
mercury. 

TURQUOIS.  Calaite;  Odontalite.  An 
opaque  gem  found  chiefly  at  Nishapur,  in 
the  province  of  Khorasan,  in  nodules  or 
as  small  veins  traversing  a  ferrugino- 
argillaceous  rock,  and  greatly  esteemed 
on  account  of  its  beautiful  blue  colour, 
which  will  in  most  cases  be  sufficient  to 
distinguish  it  both  from  the  blue  silicate 
of  copper,  and  from  fossil  bones  (parti- 
cularly teeth)  impregnated  with  blue 
phosphate  of  iron  or  carbonate  of  copper 
— the  occidental  turquoises  of  lapida- 
ries. 

TU'RRILITE.  An  extinct  genus  of 
spiral,  turreted,  chambered  shells,  allied 


ul: 


ULT 


to  the  ammonites,  having  the  siphunicle 
near  the  dorsal  margin. 

TU'TENAG.  The  commercial  name  for 
the  zinc  or  spelter  of  China,  an  alloy  used 
in  the  manufacture  of  the  gong  ;  also  the 
name  of  a  white  metallic  compound, 
called  Chinese  copper.  Impure  oxide  of 
zinc  is  called  tutty. 

TWILIGHT.  A  phenomenon  depend- 
ing on  reflection  of  the  rays  of  light  pass- 
ing through  the  atmosphere.  Before  the 
sun  becomes  visible  above  the  horizon, 
the  rays  of  light  illuminate  the  atmo- 
sphere, which  to  some  extent  reflects  and 
scatters  them  in  all  directions,  and  the 
result  is  a  faint  light  which  precedes  the 
rising  of  the  sun  and  follows  its  setting, 
and  which  we  call  twilight.  Twilight 
begins  and  terminates  when  the  sun  is 
about  18°  below  the  horizon ;  its  dura- 
tion varies  with  the  latitude;  in  some 
northern  latitudes  it  may  endure  all 
night.  The  luminous  lines  occasionally 
seen  in  the  air,  in  a  sky  full  of  partially 
broken  clouds,  which  the  vulgar  term 
"  the  sun  drawing  water,"  are  similarly 
caused. 

TYCHONIC  SYSTEM.  A  system  of 
Astronomy,  so  named  from  Tycho  Brahe, 
a  noble  Dane,  who  was  born  a.d.  1546, 
and  who  partly  restored  the  system  of 


Ptolemy  concerning  the  earth  remaining  at 
rest,  whilst  the  other  heavenly  bodies  moved 
round  it.  He  taught,  however,  that  the 
moon  performed  a  monthly  revolution 
round  the  earth;  that  the  sun  was  the 
centre  of  the  orbits  of  Mercury,  Venus, 
Mars,  Jupiter,  and  Saturn,  which  revolve 
round  him  in  their  respective  periods,  as 
he  revolves  round  the  earth  in  a  solar 
year;  and  accordingly,  that  these  five 
planets,  together  with  the  sun,  are  car- 
ried round  the  earth  in  twenty-four  hours. 
TYPE  METAL.  An  alloy  of  lead  and 
antimony,  used  in  casting  printer's  types. 
TYPHLOPHTHA'LMES  (Tv<p\6s, 
blind,  b<p0a\n6s,  the  eye).  A  family  of 
Scincoidans,  comprising  those  Saurians 
which  are  completely  blind,  or  whose 
eyes  are  so  small  that  they  seem  scarcely 
to  exist,  except  in  a  rudimentary  state, 
and  entirely  covered  with  skin,  as  in  the 
genera  dibamus  and  typhline. 

TYPHOON  {tv<Pm,  a  whirlwind).  A 
hot  wind  which  occasionally  blows  with 
great  violence  in  Africa,  Syria,  Arabia, 
and  Persia.  It  is  known  in  Egypt  by  the 
name  of  sirocco,  in  Arabia  as  the  simoon, 
and  on  the  coast  of  Guinea  as  the  har- 
mattan.  The  term  is  frequently  applied 
to  a  tropical  storm. 


U 


ULLMANNITE.  Phosphate  of  man- 
ganese and  iron,  occurring  massive  at 
Limoges  in  France. 

ULMA'CEiE  (ulmus,  the  elm).  The 
Elm  tribe  of  Dicotyledonous  plants. 
Trees  and  shrubs  with  leaves  alternate  ; 
Jlowers  apetalous ;  ovarium  superior  ; 
fruit  1  or  2-celled,  indehiscent ;  seeds 
pendulous. 

ULMIC  ACID,  or  ULMIN  {ulmus,  the 
elm).  The  name  given  by  Dr.  Thomson 
to  a  brown  substance  derived  from  a  se- 
cretion of  the  elm  and  some  other  trees, 
consistinjg  of  mucilaginous  matter  com- 
bined with  potash.  Berzelius  changed 
the  name  for  that  of  geic  acid  (7^,  earth), 
because,  on  treating  soils  with  alkalis, 
a  considerable  quantity  of  a  similar  com- 
pound is  obtained.  The  peculiar  pro- 
perties of  manures,  soils,  and  what  is 
called  moss  water,  are  due  to  the  pre- 
sence of  this  substance. 

Sacchulmic  acid.  This  substance,  and 
sacchulmine,  are  formed  by  boiling  cane 
351 


sugar  for  a  very  long  time  in  dilute  sul- 
phuric, hydrochloric,  or  nitric  acid.  They 
were  supposed  to  be  identical  with  ulmic 
acid  and  ulmin,  but  Liebig  considered 
them  to  be  of  a  different  nature,  and  gave 
them  their  present  names. 

ULTIMATE  ANALYSIS.  In  che- 
mistry, the  resolution  of  substances  into 
their  absolute  elements,  as  opposed  to 
proximate  analysis,  by  which  they  are 
merely  resolved  into  secondary  com- 
pounds. These  terms  are  generally  used 
in  reference  to  organic  bodies.  Gum, 
starch,  &c,  are  proximate  principles ; 
carbon,  hydrogen,  and  oxygen,  ultimate 
principles. 

ULTIMATE  RATIO.  The  ratio  of 
evanescent  quantities.  If  two  variable 
quantities  be  supposed  constantly  to  ap- 
proach each  other  in  value,  so  that  their 
ratio  or  quotient  continually  approaches 
to  unity,  and  at  last  differs  from  unity  by 
less  than  any  assignable  quantity,  the 
ultimate  ratio  of  these  two  quantities  is 


UMB 


UND 


said  to  be  a  ratio  of  equality.  The  me- 
thod of  prime  and  ultimate  ratios  was  in- 
troduced by  Newton,  and  the  terms  re- 
late to  the  ratios  of  variable  quantities 
considered  as  receding  from,  or  approach- 
ing to,  the  ratios  of  the  limits  to  which 
they  continually  and  simultaneously  ap- 
proach. 

ULTRAMARINE.  A  blue  pigment 
of  great  permanence,  prepared  entirely, 
until  lately,  from  the  lapis  lazuli  or  lazu- 
lite.  It  is  now  made  of  silica,  alumina, 
soda,  and  sulphur. 

ULVA'CE^S  {ulva,  laver).  A  tribe  of 
cryptogamic  plants  belonging  to  the  in- 
articulate division  of  the  order  Algacece. 
They  comprise  plants  found  in  fresh  and 
salt  water,  with  a  membranous,  reticu- 
lated structure,  and  the  reproductive 
organs  imbedded  in  the  substance  of  the 
plant.  They  are  the  lavers,  the  sea- 
purse,  the  water-gut,  &c. 

UMBEL  {umbella,  an  umbrella).  A 
form  of  inflorescence,  in  which  all  the 
pedicels  of  the  flowers  proceed  from  a 
single  point,  and  are  of  equal  length  or 
corymbose.  When  each  pedicel  bears  a 
single  flower,  as  in  Eryngium,  the  umbel 
is  said  to  be  simple ;  when  each  pedicel 
divides,  and  bears  other  umbels,  as  in 
Heracleum,  the  umbel  is  termed  com- 
pound. In  the  latter  case,  the  assem- 
blage of  umbels  is  called  the  universal 
umbel,  each  of  the  secondary  umbels 
being  called  the  partial  umbel.  The 
peduncles  which  support  the  partial  um- 
bels are  called  radii. 

VMBELLI'FERJE  {umbella,  an  umbel, 
fero,  to  bear).  The  Umbel-bearing  tribe 
of  Dicotyledonous  plants.  Herbaceous 
plants,  with  leaves  usually  divided ;  flowers 
in  umbels;  calyx  entire  or  5-toothed; 
petals  5,  alternate  with  5  stamens;  ova- 
rium didymous,  with  2  styles  and  solitary 
pendulous  ovula. 

UMBER.  An  ore  of  iron  and  manga- 
nese, occurring  in  beds  with  brown  jasper 
in  the  isle  of  Cyprus,  and  used  as  a 
brown  pigment. 

UMBILI'CUS  (dim.  of  umbo,  the  boss 
of  a  shield).  1.  A  term  applied  in  con- 
chology  to  the  hollow  axis  of  those  spiral 
shells  in  which  the  inner  sides  of  the 
whorls  or  volutions  do  not  touch  one  an- 
other. 2.  In  Botany,  the  term  is  syno- 
nymous with  hilum,  and  denotes  the 
scar  where  the  seed  is  united  with  the 
placenta.  3.  The  term  has  sometimes 
been  applied  to  the  focus  of  an  ellipse  ; 
but,  in  modern  works,  it  signifies  a  point 
of  a  surface  through  which  all  its  lines  of 
352 


curvature  pass.  At  such  a  point  the  two 
principal  curvatures  are  equal. 

UMBO.  Literally,  the  boss  of  a  shield ; 
hence  applied,  in  conchology,  to  that 
point  in  a  conchifer  or  bivalve  shell 
which  constitutes  the  nucleus  or  apex 
of  each  valve,  and  which  is  generally 
situated  above  the  hinge,  and  always 
near  it. 

UMBRA.  A  shadow;  the  shadow  of 
the  earth  or  of  the  moon  in  an  eclipse. 
See  Penumbra. 

VNC1JE.  The  name  given  by  the  old 
algebraists  to  the  coefficients  of  the  letters 
in  the  expansion  of  any  power  of  a  bino- 
mial. 

UNCONFORMABLE.  A  term  applied 
to  a  set  of  geological  strata,  when  their 
planes  are  not  parallel  to  those  of  another 
set  which  are  in  contact.  See  Conformable. 
UNDE'CAGON  {undecim,  eleven, 
ywvla,  an  angle).  A  barbarous  term  for 
a  plane  figure  bounded  by  eleven  sides, 
and,  consequently,  containing  eleven 
angles.    Endecagon  is  classical. 

UNDER-SHRUB.  Suffrutex.  The 
under-shrub  differs  from  the  shrub  in 
perishing  annually,  either  wholly  or  in 
part;  and  from  the  herb,  in  having 
branches  of  a  woody  texture,  which  fre- 
quently exist  more  than  one  year.  It  is 
exactly  intermediate  between  the  shrub 
and  the  herb ;  such  is  the  mignionette  in 
its  native  country,  or  in  the  state  in 
which  it  is  known  as  the  Tree  Mignio- 
nette. 

UNDETERMINED.  This  word  is 
applied  in  Mathematics  to  a  number 
which  has  not  been  determined,  but  is 
capable  of  being  determined ;  whereas  an 
indeterminate  number  is  one  which  can- 
not be  determined  at  all  in  the  given 
case. 

UNDULATED  (undula,  a  little  wave). 
Wavy ;  a  term  nearly  synonymous  with 
sinuated,  but  more  particularly  applied 
to  the  colouring  of  shells. 

UNDULA'TION  {undula,  a  little 
wave).  A  tremulous  motion  or  vibration 
observable  in  a  fluid,  whereby  it  alter- 
nately rises  and  falls  like  the  waves  of 
the  sea.  The  constituent  particles  of  all 
bodies  are  usually  held,  by  the  operation 
of  certain  internal  and  external  forces, 
in  a  state  of  equilibrium ;  and,  where 
these  particles  have  been  to  a  certain  ex- 
tent disturbed  by  any  cause,  they  return 
to  the  state  of  equilibrium,  by  alternately 
approaching  the  position  of  rest  and  re- 
ceding from  it,  until,  by  a  gradually  de- 
creasing recession,  they  attain  the  con- 


UNG 


UNI 


dition  of  repose.  These  movements  are 
called  undulations,  vibrations,  or  oscilla- 
tions. 

1.  Progressive  undulation.  In  this 
kind  of  movement,  the  undulation  suc- 
cessively traverses  the  different  parts  of 
the  body;  those  particles  which  have 
been  immediately  excited  by  the  disturb- 
ing cause  communicating  motion  to  those 
■which  are  next  to  them,  and  so  on.  In 
this  case  the  movement  of  the  particles 
is  successive,  so  that  the  position  they 
assume  at  any  particular  moment  during 
the  continuance  of  their  motion,  appears 
to  advance  from  one  place  to  another. 

2.  Stationary  undulation.  In  this  kind 
of  movement  all  the  particles  of  a  body 
begin  their  undulations  simultaneously, 
and  complete  them  at  the  same  instant. 
Even  when  the  body  is  divided  into 
several  vibrating  portions,  each  of  them 
ceases  to  move  independently  of  the  rest, 
the  different  parts  of  the  body  being 
separated  by  points  which  remain 
throughout  in  a  state  of  rest. 

U'NDULATORY  THEORY  {undula, 
a  little  wave).  A  theory  for  explaining 
the  nature  of  light.  According  to  this, 
light  has  no  material  existence,  but  its 
phenomena  are  produced  by  the  vibra- 
tions, or  undulations,  of  a  subtle  ethereal 
fluid,  diffused  through  all  nature,  and  set 
in  motion  by  the  presence  of  luminous 
bodies.  The  phenomena  of  vision  are 
thus  produced  by  pulsations  of  ether  on 
the  retina  of  the  eye,  as  those  of  sound 
are  by  pulsations  of  air  on  the  nerve  of 
hearing.     See  Emission. 

UNEQUALLY  PINNATE.  Impari- 
pinnate.  That  modification  of  the  pin- 
nate leaf,  in  which  an  odd  leaflet  termi- 
nates the  petiole. 

UNGUICULA'TA  (unguis,  a  claw). 
Clawed  animals  ;  a  section  of  the  Mam- 
malia, comprising  those  which  have  the 
digits  armed  with  claws,  but  free  for  the 
exercise  of  touch  upon  their  under  sur- 
face. The  feet  of  these  animals  are  bifid 
in  the  camel,  multifid  in  the  elephant, 
the  ape,  &c. 

UNGUIS.  The  Latin  term  for  a  nail. 
In  Botany,!  it  denotes  the  lower  part  of  a 
petal  which  tapers  conspicuously  towards 
the  base,  as  in  the  pink.  The  upper  part 
is  called  the  limb.  The  petal  itself  is 
termed  unguiculate. 

U'NGULA.  A  hoof;  and,  from  the  re- 
semblance of  this  part  of  the  animal  to 
that  part  of  a  cone  which  is  separated  from 
the  portion  containing  the  vertex  by  an 
oblique  plane,  such  a  solid  is  called  an 
353 


ungula,  and  rules  for  determining  its  con- 
tent are  given  in  books  of  mensuration. 

UNGULA'TA  (ungula,  a  hoof).  Hoofed 
animals  ;  a  section  of  the  Mammalia, 
comprising  those  species  which  have  the 
digits  enclosed  in  hoofs,  the  under  sur- 
face not  being  left  free  for  the  exercise 
of  touch.  The  hoof  is  solidipedous  in  the 
horse,  bisulcate  in  the  ox,  the  goat,  &c. 

U'NIFORM.  Though  this  word  means 
nothing  more  than  "of  one  form,"  it  has 
a  signification  in  mathematics  which 
might  be  better  rendered  by  "  of  one 
value,"  or  "of  one  degree,"  when  we 
speak  to  the  mathematical  proficient. 
But  it  is  a  convenience,  though  only  an 
accidental  one.  that  the  word  does  not 
imply  the  idea  of  value  absolutely.  Pen. 
Cycl. 

UNILOCULAR  (unus  loculus,  one 
cell).  The  designation  of  shells  which 
are  not  divided  into  chambers ;  of  seed- 
vessels  which  are  not  separated  into 
cells. 

UNIO'NIOffi.  River  Mussels  or 
Unios;  a  family  of  atrachian  bivalves, 
which  unite  the  atrachian  with  the  ma- 
crotrachian  mollusca. 

UNIPE'LTATES  (una  pelta,  one 
buckler).  A  family  of  stomapodous 
crustaceans,  including  those  in  which 
the  carapace  is  composed  of  a  single 
shield-like  plate. 

UNIPO'LAR.  A  term  applied  by  Ehr- 
man  to  substances  of  imperfect  conduct- 
ing power,  which  are  capable  of  receiving 
only  one  kind  of  electricity,  when  made 
to  form  links  in  the  voltaic  chain. 

UNIT  JAR.  An  apparatus  contrived 
by  Mr.  Harris  for  charging  Leyden  jars 
with  known  proportions  of  electricity,  the 
quantity  of  electricity  employed  being 
proportioned  to  the  number  of  charges. 

UNIT  OF  MEASURE.  A  term  ap- 
plied in  Geometry  to  a  line  by  which  an- 
other is  measured ;  that  is,  which  is  ap- 
plied to  another  line,  in  order  to  deter- 
mine the  number  of  times  that  the  latter 
contains  it.  The  primary  unit  by  which 
angles  and  their  corresponding  arcs  are 
numerically  expressed,  is  the  degree  or 
the  ninetieth  part  of  a  right  angle  or  of  a 
quadrant. 

UNIVALVES  (unus,  one,  valves,  fold- 
ing-doors). A  class  of  mollusks,  whose 
shell  is  composed  of  one  piece,  generally 
with  spiral  volutions. 

UNIVERSAL  PROPOSITION.  A 
proposition  whose  predicate  is  affirmed 
or  denied  of  the  whole  of  the  subject. 
Thus,  in  the  language  of  logic,  we  have 


URA 


URI 


universal  affirmative  and  universal  nega- 
tive propositions,  in  which  the  universal 
signs  "all,"  "no,"  "every,"  are  em- 
ployed to  indicate  that  the  subject  is 
distributed. 

UNIVERSE;  WORLD.  The  former 
of  these  terms  usually  relates  to  all 
created  things,  and  hence  the  theory  of 
the  Universe  comprises  all  that  is  known 
or  conceived  of  the  general  arrangement 
of  the  stars,  planets,  &c.  The  term 
world  was  formerly  synonymous  with  the 
present  term  universe,  but  is  now  com- 
monly restricted  to  our  own  planet. 

UNI'VOCAL  NOUN.  In  Logic,  a 
common  term  is  called  univocal  in  re- 
spect of  those  things  or  persons  to  which 
it  is  applicable  in  the  same  signification, 
as  the  term  "  man."  Whately  observes 
that  "  the  usual  divisions  of  nouns  into 
univocal,  equivocal,  and  analogous,  and 
into  nouns  of  the  first  and  second  inten- 
tion, are  not,  strictly  speaking,  divisions 
of  words,  but  divisions  of  the  manner  of 
employing  them  ;  the  same  word  may  be 
employed  either  univocally,  equivocally, 
or  analogously ;  either  in  the  first  inten- 
tion or  in  the  second.  The  ordinary 
logical  treatises  often  occasion  great  per- 
plexity to  the  learner,  by  not  noticing 
this  circumstance,  but  rather  leading  him 
to  suppose  the  contrary." 

UNLIMITED.  A  term  sometimes 
employed  by  mathematicians  in  the  sense 
of  indefinite,  in  order  to  avoid  the  use  of 
the  word  infinite.  It  is  also  used  to  de- 
scribe a  problem  which  may  admit  of  an 
infinite  number  of  answers. 

UNSTRA'TIFIED  ROCKS.  Rocks 
which  are  not  disposed  in  beds  or  strata. 
These  are  also  called  massive  and  over- 
lying rocks,  and  comprise  those  usually 
termed  Plutonic,  Igneous,  Trap,  &c. 
Many  of  these  are  so  intimately  related 
to  granite,  as  scarcely  to  be  distinguished 
from  it,  while  others  as  obviously  pass 
into  lava  and  other  products  of  active 
volcanoes. 

UPU'PID^E.  The  Hoopoe  tribe;  a 
family  of  the  Insessores,  or  Perching 
birds,  named  from  the  upupa,  or  hoopoe, 
the  last  genus  of  Cuvier's  Tenuirostres. 

U'RAMIL.  A  crystalline  substance 
obtained  by  treating  a  hot  saturated  solu- 
tion of  thionurate  of  ammonia  with  hy- 
drochloric acid  in  excess.  By  decom- 
posing this  substance  an  acid  is  obtained, 
called  the  uramilic. 

URANGLI'MMER.     An  ore  of  ura- 
mium,   formerly  called  green  mica,  and 
by  Werner  chalcolite.    See  Uranite. 
354 


U'RANITE.  The  yellow  uranite  or 
uran  mica,  and  the  green  uranite  or 
chalcolite,  are  phosphates  of  oxide  of  ura- 
nium ;  they  are  distinguished  by  the 
former  containing  a  small  portion  of 
phosphate  of  lime,  and  the  latter  an 
equivalent  portion  of  phosphate  of 
copper. 

URANIUM.  A  metal  discovered  in 
1781,  in  the  mineral  called,  from  its  black 
colour,  pitch-blende.  It  was  named  by 
Klaproth  after  the  new  planet  Uranus, 
the  discovery  of  which  took  place  in  the 
same  year. 

U'RANOCHRE.  An  ore  of  uranium, 
containing  this  metal  in  the  oxidised 
state. 

URANO'GRAPHY  (oipavos,  the  hea- 
vens, 7pa0w,  to  describe).  A  subordinate 
department  of  the  science  of  astronomy, 
presenting  an  account  of  the  arrange- 
ments which  have  been  made  by  astro- 
nomers for  delineating  the  starry  heavens, 
and  working  the  many  mathematical  pro- 
blems of  which  they  are  the  subject. 

U'RANUS  or  HERSCHEL.  A  planet 
discovered  by  Sir  W.  Herschel  in  1781, 
March  13.  Its  apparent  diameter  is 
about  4",  from  which  it  never  varies 
much,  owing  to  the  smallness  of  our 
orbit  in  comparison  of  its  own.  Its  real 
diameter  is  about  35,000  miles,  and  its 
bulk  80  times  that  of  the  earth.  It  is 
attended  by  satellites — two  at  least,  pro- 
bably five  or  six — whose  orbits  offer  re- 
markable peculiarities. 

URAO.  A  variety  of  sesqui-carbonate 
of  soda,  found  in  Columbia. 

URATES.  Compounds  of  uric  or 
lithic  acid  with  the  salifiable  bases. 

U'RCEOLUS  (dim.  of  urceus,  a  water 
pitcher).  A  small  pitcher-like  body, 
formed  by  the  two  bracts  which,  in  the 
genus  Carex,  become  confluent  at  their 
edges,  and  enclose  the  pistil. 

U'REA.  Anormal  cyanite  of  am- 
monia. A  substance  existing  in  the 
form  of  lactate  of  urea  in  human  urine, 
and  combined  with  hippuric  acid  in  that 
of  the  cow  and  elephant. 

U'RETHANE.  The  name  given  by 
Dumas  to  a  substance  which  he  con- 
sidered to  be  a  combination  of  urea  with 
carbonic  ether.  It  is  also  considered  as 
a  chloroxicarbonic  ether,  in  which  the 
chlorine  is  replaced  by  amidogen. 

URIC  ACID  {olpov,  urine).  Lithic 
acid.  An  acid  existing  in  the  urine  of  all 
carnivorous  animals,  and  forming  the  ba- 
sis of  most  urinary  concretions.  It  forms, 
in  combination  with  ammonia,  the  white 


V  AG 


V  AL 


part  of  the  excrement  of  birds ;  and  vast 
accumulations  of  that  urate  exist  in  the 
■guano,  or  decomposed  excrement  of 
aquatic  birds,  by  which  many  of  the 
small  islands  on  the  Coast  of  Peru  and 
Chili  are  covered,  and  which  is  used  as  a 
manure. 

URILE.  A  compound  radical,  sup- 
posed to  exist  in  uric  acid  and  the  pro- 
ducts of  its  decomposition.  It  is  a  com- 
pound of  2  atoms  of  cyanogen  and  4 
atoms  of  carbonic  oxide. 

URN.  The  peculiar  theca  or  capsule 
of  mosses,  containing  the  spores.  It 
is  placed  at  the  apex  of  a  stalk  or 
seta,  bearing  on  its  summit  a  hood  or 
calyptra,  and  closed  by  a  lid  or  opercu- 
lum. 

URODEL  A.  An  order  of  Amphibious 
animals,  including  the  Salamanders, 
Water-newts,  &c,  in  which  the  gills  dis- 
appear in  the  perfect  state,  but  the  tail  is 
retained.  They  may  be  distinguished 
into  the  Tritons,  which,  like  the  frogs, 
exhibit  aquatic  habits  even  in  the  adult 
state ;  and  the  true  Salamanders,  which 
are  more  analogous  to  the  toads  in  their 
appearance  and  habits. 

URSA  MAJOR.  The  Great  Bear ;  a 
northern  constellation,  consisting  of  87  I 


stars,  the  principal  of  which  is  named 
Dubhe. 

Ursa  Minor.  The  Lesser  Bear ;  a 
northern  constellation,  consisting  of  24 
stars,  the  principal  of  which  is  the  Pole 
Star. 

UR'SIDjE  (ursus,  a  bear).  The  Bear 
tribe  of  carnivorous  vertebrate  ani- 
mals. These  are  the  true  plantigrade 
carnivora.  Most  of  them  possess  several 
tuberculous  teeth. 

URTICA'CEjE  (urtica,  a  nettle).  The 
Nettle  tribe  of  Dicotyledonous  plants. 
Trees  or  shrubs  with  leaves  alternate; 
flowers  apetalous,  solitary,  or  clustered ; 
ovarium  superior  2-celled ;  fruit,  a  simple 
indehiscent  nut. 

UTRICLE  (utriculus,  dim.  of  uter,  a 
leathern  bag).  Cystidium.  In  Botany, 
a  simple  fruit,  1-celled,  one  or  few- 
seeded,  superior,  membranous,  fre- 
quently dehiscent  by  a  transverse  in- 
cision. It  may  be  described  as  a  cary- 
opsis,  the  pericarp  of  which  has  no  adhe- 
sion with  the  integuments  of  the  seeds. 
It  differs  from  the  pyxidium  in  texture, 
being  strictly  simple,  that  is,  not  pro- 
ceeding from  an  ovarium  with  obliterated 
dissepiments.  It  occurs  in  the  ama- 
ranth, in  chenopodium,  &c. 


VA'CUUM  {vacuus,  empty).  Literally, 
an  empty  place,  or  space  void  of  matter. 
This  term  generally  denotes  the  space 
enclosed  by  a  vessel  from  which  the 
atmospheric  air  and  every  other  gas  has 
been  excluded,  as  in  the  Torricellian 
vacuum  above  the  surface  of  the  mer- 
cury in  the  barometer  tube,  and  the  Gue- 
rickian  or  Boylean  vacuum  of  the  air- 
pump.  The  latter  vacuum  is  always  im- 
perfect ;  the  vessel  is,  nevertheless, 
called  an  exhausted  receiver. 

VAGA'NTES  (vagor,  to  wander).  A 
tribe  of  spiders  comprising  those  which 
watch  their  prey  from  the  web,  and  also 
frequently  run  with  agility  in  pursuit 
of  their  prey. 

VAGATRI'CES  (vagor,  to  wander). 
Wanderers  ;  an  order  of  birds,  which, 
being  equally  well  adapted  for  walking 
and  for  flying,  might  be  designated  ter- 
restrial. They  walk  with  ease,  leap  under 
excitement,  or  even  run  with  consider- 
able speed.  They  include  the  corvine  and 
the  graculine  bir*u 
355 


VAGI'NA.  Literally,  a  sheath;  and 
hence  applied,  in  Botany,  to  a  leafy  ex- 
pansion surrounding  the  stem  of  some 
monocotyledonous  plants ;  occasionally 
the  petiole  embraces  the  branch  from 
which  it  springs,  and  in  such  case  is 
said  to  be  sheathing,  and  is  even  called  a 
sheath,  or  vagina,  as  in  grasses. 

VA'GINATED  (vagina,  a  sheath).  A 
designation  of  those  polyps  which  are  en- 
closed in  a  calcareous  sheath  or  tube, 
and  are  also  called  tubiporidce. 

VALERIANATES.  The  Valerian 
tribe  of  Dicotyledonous  plants.  Herbs 
with  leaves  opposite ;  flowers  corymbose, 
panicled,  or  in  heads ;  stamens  distinct ; 
ovarium  inferior  2-celled ;  fruit  dry, 
indehiscent. 

VALERIANIC  ACID.  Valeric  acid. 
An  acid  obtained  by  distillation  of  the 
root  of  the  Valeriana  officinalis  with  water, 
as  long  as  it  reddens  litmus.  Its  salts 
are  called  valerianates  and  valerates. 

VALLEY  (vallis).  A  space  lying  be- 
tween opposite  ridges  of  mountains  or  of 


VAL 

hills,  its  lowest  part  being  commonly  the 
bed  of  some  torrent  or  river,  which  ori- 
ginates in  the  higher  grounds.  A  level 
space  of  great  breadth,  separating  two 
mountain-ranges,  is  not,  properly  speak- 
ing, a  valley,  but  a  plain.  The  same  re- 
mark applies  to  "circular  valleys,"  as 
that  of  Bohemia,  200  miles  in  diameter, 
and  that  of  Cashmere,  90  miles  in  dia- 
meter, which  are  rather  plains  sur- 
rounded by  mountains. 

VALUE.  Value  is  the  only  relation 
with  which  Political  Economy  is  con- 
versant ;  yet  there  is  no  subject  as  to  the 
meaning  of  which  economists  are  less 
agreed.  Whately  points  out  the  incon- 
sistencies of  writers  on  this  topic  : — 

1.  "The  popular,  and  far  the  most 
convenient,  use  of  the  word,  is  to  signify 
the  capacity  of  being  given  and  received 
in  exchange.  So  defined  it  expresses  a 
relation.  The  value  of  any  one  thing 
must  consist  in  the  several  quantities  of 
all  other  things  which  can  be  obtained  in 
exchange  for  it,  and  can  never  remain 
fixed  for  an  instant.  Most  writers  admit 
the  propriety  of  this  definition  at  the 
outset,  but  they  scarcely  ever  adhere 
to  it. 

2.  "Adam  Smith  defines  Value  to 
mean  either  the  utility  of  a  particular 
object,  or  the  power  of  purchasing  other 
goods  which  the  possession  of  that  object 
conveys.  The  first  he  calls  'Value  in 
use,'  the  second  '  Value  in  exchange.' 
But  he  soon  afterwards  says,  that  equal 
quantities  of  labour  at  all  times  and 
places  are  of  equal  value  to  the  labourer, 
whatever  may  be  the  quantity  of  goods 
he  receives  in  return  for  them  ;  and  that 
labour  never  varies  in  its  own  value.  It 
is  clear  that  he  affixed,  or  thought  he  had 
affixed,  some  other  meaning  to  the  word ; 
as  the  first  of  these  propositions  is  con- 
tradictory, and  the  second  false,  which- 
ever of  his  two  definitions  we  adopt. 

3.  "Mr.  Ricardo  appears  to  set  out  by 
admitting  Adam  Smith's  definition  of 
Value  in  exchange.  But  in  the  greater 
part  of  his  '  Principles  of  Political  Eco- 
nomy,' he  uses  the  word  as  synonymous 
with  Cost;  and  by  this  one  ambiguity 
has  rendered  his  great  work  a  long 
enigma. 

4.  "  Mr.  Malthus  defines  Value  to  be 
the  power  of  purchasing.  In  the  very 
next  page  he  distinguishes  absolute  from 
relative  value,  a  distinction  contradictory 
to  his  definition  of  the  term,  as  expres- 
sive of  a  relation. 

5.  "  Mr.  M'Culloch   distinguishes  be- 

356 


VAL 

tween  real  and  exchangeable,  or  relative, 
value.  And  in  his  nomenclature,  the  ex- 
changeable, or  relative,  value  of  a  com 
modity  consists  in  its  capacity  of  pur- 
chasing ;— its  real  value  in  the  quantity 
of  labour  required  for  its  production  ct 
appropriation. 

6.  "All  these  differences  appear  ta 
arise  from  a  confusion  of  cause  and  effect. 
Having  decided  that  commodities  are 
valuable  in  proportion  to  the  labour  they 
have  respectively  cost,  it  was  natural  to 
call  that  labour  their  Value." 

VALVE  {valvce,  folding-doors).  A  close 
lid  affixed  to  a  tube  or  an  opening  in 
some  vessel,  by  means  of  a  hinge,  and 
which  can  be  opened  only  in  one  direc- 
tion. Hence,  the  more  forcibly  it  is 
pressed  in  the  other  direction,  the  closer 
it  shuts  the  aperture,  so  that  it  either 
admits  the  entrance  of  a  fluid  and  pre- 
vents its  return,  or  admits  its  escape  and 
prevents  its  re-entrance. 

1.  The  clack-valve,  or  ordinary  pump- 
valve,  is  of  a  circular  form,  and  consists 
of  a  flat  piece  of  leather  rather  larger 
than  the  aperture  it  is  intended  to  close. 
It  should  open  at  an  angle  of  30°,  so  as 
to  admit  of  a  free  passage,  equal  to  its 
aperture.  The  double-clack,  or  butterfly- 
valve,  consists  of  two  semicircular  valves, 
commonly  employed  for  pump-buckets, 
and  have  the  advantage  of  allowing  less 
water  to  escape  into  the  well  or  cistern 
while  in  the  act  of  closing  the  orifice. 
Clack-valves  consist  sometimes  of  four 
sectors  of  circles,  the  angular  points  of 
which  meet  vertically  over  the  centre  of 
the  orifice,  the  sides  being  disposed  like 
those  of  a  quadrangular  pyramid. 

2.  The  conical  or  spindle  valve  consists 
of  a  flat  circular  plate  of  metal,  having 
its  rim  bevelled  and  ground  so  as  to  fit  in 
a  conical  seat  or  nozzle.  Its  form  is  that 
of  the  frustum  of  a  cone,  the  side  of 
which  makes  an  angle  of  45°  with  a  dia- 
meter of  the  base.  It  is  usually  employed 
as  the  safety-valve  of  the  boiler  of  a 
steam-engine.  The  diameter  of  the  valve- 
box  should  be  to  the  greater  diameter  of 
the  valve  as  3  to  2 ;  and  the  valve  should 
not  rise  less  than  one-fourth  of  its  greater 
diameter  when  quite  open ;  but  both 
these  proportions  must  be  increased  if 
the  valve  be  out  of  the  centre  of  the 
box. 

3.  The  button-valve  or  puppet-clack  re- 
sembles the  preceding  valve,  in  being  of 
a  circular  form,  with  a  conical  side,  and 
having  a  vertical  direction ;  this  is  ef- 
fected by  means  of  a  guide-rod,  which  is 


V  AL 


VAR 


attached  to  the  centre  of  the  plate  per- 
pendicularly to  its  surface,  and  moves 
freely  up  and  down  in  a  perforation  in 
each  of  two  hars  fixed  diametrically 
across,  and  near  the  top  and  bottom  of 
the  orifice. 

4.  The  spherical  valve  is  a  modification 
of  the  conical  valve :  the  seat  or  nozzle 
represents  a  portion  of  a  sphere;  the 
valve  itself  may  also  be  a  portion  of  a 
sphere,  or  an  entire  sphere.  It  has  been 
recommended  as  a  safety-valve,  to  pre- 
vent the  danger  of  adhering  in  the  boilers 
of  steam  vessels.  It  is  also  called  a  cup- 
valve. 

5.  The  throttle-valve  has,  instead  of 
the  reciprocating  motion  of  the  valves 
already  noticed,  a  rotary  motion.  Its 
action  is  that  of  the  flood-gate  of  a  mill ; 
its  purpose  is  to  regulate  the  power  of  a 
steam-engine,  by  increasing  or  diminish- 
ing the  area  of  the  steam-tube  of  a 
steam-engine,  and  thus  to  increase  or 
diminish  the  amount  of  steam  supplied 
to  the  cylinder.  The  name  of  this  valve 
suggests  its  use:  the  steam- tube  is  throt- 
tled by  it. 

6.  The  sliding  valve  is  one  which  does 
not  rise  from,  and  fall  into,  a  seat  or 
nozzle,  but  slides  on  and  off  its  aperture  ; 
hence,  it  is  commonly  called  a  slide.  In 
modern  steam-engines,  the  steam  pas- 
sages are  opened  and  closed  by  the  action 
of  a  single  slide,  which  performs  the  office 
of  four  valves.  To  this  head  belong  the 
slides  of  Seaward,  Murray,  Murdock,  &c. 
The  last  of  these,  from  its  semi-cylin- 
drical form,  is  commonly  called  the 
D-slide. 

7.  The  single  cock  is  a  kind  of  valve 
consisting  of  a  plug  of  a  nearly  cylindri- 
cal shape,  inserted  into  a  hole  of  cor- 
responding form  and  dimensions  in  a 
tube ;  the  plug  is  perforated  by  a  large 
hole,  and  turned  by  a  handle  outside  the 
tube.  The  four-passaged  cock  is  a  con- 
trivance, founded  on  the  principle  of  the 
common  cock,  for  putting  four  passages 
into  communication  with  each  other, 
alternately  by  pairs  ;  it  is  used  in  steam- 
engines  for  establishing  communications 
between  the  boiler,  two  cylinders,  and  the 
external  air.  Instead  of  this  apparatus, 
two  doubled-passaged  cocks  may  be  em- 
ployed :  the  four-passaged  becomes  a 
double-passaged  cock  by  obliteration  of 
one  of  the  passages. 

VALVES  (in  Botany).     1.  A  term  ap- 
plied to  the    parts    into  which    certain 
fruits  separate,   exhibiting  the  various 
forms  of  valvular  dehiscence — the  septi- 
357 


cidal,  the  loculicidal,  and  the  septifragal ; 
the  axis  of  the  fruit  from  which  the 
valves  separate  in  cases  where  a  distinct 
axis  exists,  is  called  the  columella.  2.  The 
term  valve  has  been  also  applied  collec- 
tively to  the  three  classes  of  bracts  of 
which  the  flower  of  grasses  is  composed. 
3.  It  also  denotes  the  opening  in  the 
cells  of  anthers,  which  occurs  when  the 
pollen  is  about  to  be  discharged. 

VALVES  (in  Zoology).  The  term 
valves  denotes  the  two  ordinary  or  prin- 
cipal pieces  which  form  the  covering  of 
the  acephalous  testacea,  or  bivalves. 

VANA'DIUM  (Vanadis,  a  Scandina- 
vian deity).  A  rare  metal  discovered  by 
Sefstrcem  in  1830,  in  the  iron  prepared 
from  the  iron  ore  of  Taberg,  in  Sweden, 
and  procured  afterwards  in  larger  quan- 
tity from  the  slag  of  that  ore.  It  was 
subsequently  discovered  in  a  new  mine- 
ral, the  vanadiate  of  lead.  It  occurs  in 
the  state  of  vanadic  acid. 

VANISHING  QUANTITY.  In  Ma- 
thematics, a  quantity  is  said  to  vanish, 
or  to  become  evanescent,  when  its  arith- 
metical value  is  nothing,  or  denoted  by  0. 
See  Fraction. 

VAPORIZATION.  The  conversion 
of  a  liquid  or  of  a  solid  budy  into  vapour 
by  the  application  of  heat.  It  comprises 
the  phenomena  of  evaporation  and  of 
ebullition.  When  solid  bodies  are  vapor- 
ized and  subsequently  condensed,  the 
operation  is  termed  sublimation,  and  it 
is  employed  for  the  purification  of  cer- 
tain substances,  and  for  other  pur- 
poses. 

VAPOUR.  A  light,  expansible,  and 
generally  invisible  gas,  resembling  air 
completely  in  its  mechanical  properties, 
while  it  exists,  but  subject  to  be  con- 
densed into  the  liquid  or  the  solid  form 
by  cold.  Vaporizable  bodies  are  termed  vo- 
latile ;  while  those  which  resist  the  heat 
of  the  furnace  without  undergoing  vapor- 
ization, are  said  to  he  fixed  in  the  fire. 

Vapour,  atmospheric.  The  watery 
vapour  existing  in  the  atmosphere  from 
contact  with  the  surface  of  the  sea,  of 
lakes,  of  rivers,  and  of  humid  soil.  Its 
quantity  is  limited  by  temperature,  and 
when  this  is  reduced,  the  watery  vapour 
is  condensed,  and  becomes  visible  in  the 
form  of  dew,  clouds,  rain,  &c.  Vapour, 
when  visible,  is  termed  vesicular,  from  its 
appearing,  in  that  state,  in  the  form  of 
minute  vesicles. 

VARA'NIDiE  {Faranus,  the  monitor). 
The  Monitors ;  a  family  of  Lizards, 
known  as  the  Platynote  or  Broad-backed 


VAR 

Saurians,  arranged  by  Linnaeus  under 
the  great  genus  Lacerta. 

VAREC.  The  French  name  for  kelp, 
or  incinerated  sea-weed. 

VARIABLE  MOTION.  In  Mecha- 
nics, a  variable  motion  is  that  which  is 
produced  by  the  action  of  a  force  which 
varies  in  intensity,  or  which  continues 
to  act  after  motion  has  been  communi- 
cated to  it. 

VARIABLE  QUANTITY.  In  Ma- 
thematics, a  quantity  is  called  variable, 
which  continually  increases  or  decreases, 
asdistinguished  from  a  constant  quantity, 
which  remains  always  the  same.  Thus, 
the  abscissas  and  the  ordinates  of  an 
ellipsis,  or  other  curve  line,  are  variable 
quantities,  because  they  vary  or  change 
their  magnitudes  together.  The  dia- 
meter of  a  circle  and  the  parameter  of  a 
conic  section  are  constant,  while  their 
abscissas  are  variable.  Variable  quan- 
tities are  usually  denoted  by  the  last 
letters  of  the  alphabet,  x,  y,  z,  while  the 
constant  are  denoted  by  the  first  a,  b,  c. 
VARIABLE  STARS.  Stars  which 
undergo  a  periodical  increase  and  dimi- 
nution of  their  lustre.  The  star  called 
Algol,  or  /?  Persei,  is  usually  visible  as  a 
star  of  the  second  magnitude,  and  such  it 
continues  for  the  space  of  2d.  14h.,  when 
it  suddenly  begins  to  diminish  in  splen- 
dour, and  in  about  3£  hours  is  reduced  to 
the  fourth  magnitude.  It  then  begins 
again  to  increase,  and  in  3|  hours  more 
is  restored  to  its  usual  brightness,  going 
through  all  its  changes  in  2d.  20h.  48m., 
or  thereabouts.  This  remarkable  law  of 
variation  suggests  the  revolution  round 
it  of  some  opaque  body,  which,  when  in- 
terposed between  us  and  Algol,  cuts  off" 
a  large  portion  of  its  light.    Herschel. 

VARIATION.  An  algebraical  rule 
for  investigating  the  relation  which  vary- 
ing and  dependent  quantities  bear  to 
each  other.  When  one  quantity  y  de- 
pends upon  another  x,  in  such  a  manner 
that  if  x  is  changed  in  value,  the  value 
of  y  is  changed  in  the  same  proportion, 
then  y  is  said  to  vary  directly  as  x,  or, 
shortly,  to  vary  as  x.  Variation  is  merely 
an  abridgment  of  Proportion ;  for  one 
quantity  is  said  to  "  vary  "  as  another, 
not  because  the  two  increase  and  de- 
crease together,  but  because  as  one  in- 
creases or  decreases,  the  other  increases 
or  decreases  in  the  same  proportion.  The 
sign  used  to  denote  variation  is  oc  (read 
varies  as).     Thus,  ar2  +  3x  oc  2x*  +  6x, 

-i  I,   whatever  be   the 


since 


2x*  +  6x 


358 


VAR 

value  of  x.  Single  and  Double  Rule  of 
Three  sums  are  solved  upon  the  prin- 
ciples of  Variation  and  Proportion. 

1.  One  quantity  is  said  to  vary  directly 
as  another,  when  the  two  quantities  de- 
pend wholly  upon  each  other,  and  in 
such  a  manner,  that,  if  one  be  changed, 
the  other  is  changed  in  the  same  propor- 
tion. If  the  altitude  of  a  triangle  be  in- 
variable, the  area  varies  as  the  base. 

2.  One  quantity  is  said  to  vary  in- 
versely as  another,  when  the  former  can- 
not be  changed  in  any  manner,  but  the 
reciprocal  of  the  latter  is  changed  in  the 
same  proportion.  If  the  area  of  a  triangle 
be  given,  the  base  varies  inversely  as  the 
perpendicular  altitude. 

3.  One  quantity  is  said  to  vary  as  two 
others  jointly,  if,  when  the  former  is 
changed  in  any  manner,  the  product  of 
the  other  two  be  changed  in  the  same 
proportion.  The  area  of  a  triangle  varies 
as  its  base  and  perpendicular  altitude 
jointly. 

4.  One  quantity  is  said  to  vary  directly 
as  a  second  and  inversely  as  a  third,  when 
the  first  cannot  be  changed  in  any  man- 
ner, but  the  second  multiplied  by  the 
reciprocal  of  the  third  is  changed  in  the 
same  proportion.  The  base  of  a  triangle 
varies  as  the  area  directly  and  the  per- 
pendicular altitude  inversely. 

VARIATION  OF  THE  COMPASS. 
This  term,  as  well  as  the  expressions, 
"variation  of  the  needle  "  and  "  declina- 
tion of  the  needle,"  denotes  the  angle 
which  a  vertical  plane  passing  through 
the  axis  of  a  magnetized  needle  makes 
with  the  geographical  meridian  of  a  ship 
or  station ;  and  as,  for  the  purposes  of 
navigation,  the  needle  is  made  to  traverse 
horizontally,  the  variation  becomes  the 
angle  between  the  magnetic  axis  of  the 
needle  and  a  meridian  line  passing  par- 
allel to  the  horizon  through  the  centre 
of  the  compass. 

VARIATION  OF  CURVATURE. 
The  change  of  curvature  which  takes 
place  in  passing  from  one  point  of  a 
curve  to  another.  In  the  conic  sections, 
the  variation  of  curvature  at  any  point 
is  proportional  to  the  tangent  of  the  angle 
included  between  the  diameter  and  the 
normal,  both  of  these  passing  through 
that  point.  The  circle  is  the  only  curve 
in  which  the  curvature  is  uniform  at 
every  point. 

VARIATIONS,  BAROMETRICAL. 
The  changes  in  the  altitude  of  the  baro- 
meter at  the  same  place  are  in  part  regu- 
lar, and  in    part   extremely   irregular. 


VAR 


VAR 


The  regular  variations  occur  almost 
always  at  the  same  time  of  day,  attain- 
ing daily  two  minima  and  two  maxima. 
They  show  that  an  ebb  and  a  flow  take 
place  in  the  atmosphere,  similar  to  what 
is  observed  in  the  sea.  These  are  very 
small,  the  oscillation  seldom  amounting 
to  more  than  a  line,  and  are,  for  the  most 
part,  observable  only  in  the  torrid  zone. 
The  irregular  changes  are  much  greater 
in  degree  than  the  regular,  and  are  more 
frequent  and  observable  as  we  approach 
tbe  poles ;  for  this  reason  less  notice  is 
paid  by  us  to  the  regular  alterations  in 
the  height  of  the  mercury. 

VARIATIONS,  CALCULUS  OF. 
"  When  a  quantity  is  subject  to  one  sort 
of  variation  only,  the  consideration  of 
that  variation  belongs  to  the  simple  dif- 
ferential calculus;  but  when  it  is  sub- 
ject to  two  or  more  distinct  sorts  of  vari- 
ation, suppose  that  of  the  differential  cal- 
culus and  another,  then  the  mode  of  deal- 
ing with  the  second  sort  of  variation 
is  said  to  belong  to  the  calculus  of  vari- 
ations." 

Illustration.  "In  Dynamics,  for  ex- 
ample, there  are  two  distinct  species  of 
motion  to  consider :  one  which,  at  the 
end  of  the  time  t,  the  system  is  about  to 
take  during  the  ensuing  time  dt  in  con- 
sequence of  the  velocities  acquired  by  its 
particles ;  and  another  which,  without 
any  consideration  of  the  first,  must  be 
impressed  upon  it  for  the  examination  of 
the  conditions  which  express  the  equi- 
valence of  the  impressed  and  effective 
forces.  Here  then  is  a  case  for  the  cal- 
culus of  variations." — Pen.  Cycl. 

VARIATIONS,  PERIODIC  and  SE- 
CULAR. In  the  language  of  Astronomy, 
the  term  variation  denotes  a  change  of 
inclination  of  the  orbit  of  a  planet  occa- 
sioned by  a  disturbing  body.  When  these 
changes  are  compensated  by  the  configu- 
rations of  the  disturbed  and  the  disturb- 
ing body  with  each  other,  and  therefore 
in  comparatively  short  periods,  they  are 
called  periodic  variations ;  and  tbe  devi- 
ations, thus  compensated,  are  called  in- 
equalities depending  on  configurations. 
When  the  compensation  is  operated  by  a 
period  of  the  node,  it  has  nothing  to  do 
with  the  configurations  of  the  bodies,  but 
requires  an  immense  period  of  time  for 
its  consummation,  and  is,  therefore,  dis- 
tinguished from  the  former  by  the  term 
secular  variation. 

The  variation  of  the  moon  is  an  in- 
equality of  the  moon's  motion,  depending 
on  the  angular  distance  of  this  body  from 
359 


the  sun.  It  arises  from  that  part  of  the 
sun's  disturbing  force  which  is  at  right 
angles  to  the  radius  vector,  and  which 
accelerates  the  motion  of  the  moon  from 
the  quadratures  to  the  syzygies,  and  re- 
tards it  from  the  syzygies  to  the  quadra- 
tures. 

VARIEGATION  IN  PLANTS.  A 
general  term  denoting  the  arrangement 
of  two  or  more  colours  in  the  leaves, 
petals,  and  other  parts  of  plants.  These 
parts  are  said  to  be  marbled,  when  a  sur- 
face is  traversed  by  irregular  veins  of 
colour,  like  a  biock  of  marble ;  discoidal, 
when  there  is  a  single  large  spot  of  colour 
in  the  centre  of  some  other  colour ;  ocel- 
lated,  when  a  broad  spot  of  some  colour 
has  another  spot  of  a  different  colour 
within  it,  like  a  little  eye;  tessellated, 
when  the  colours  are  disposed  in  small 
squares,  like  those  of  a  tessellated  pave- 
ment ;  lettered,  when  the  spots  of  colour 
present  the  form  and  appearance  of 
letters.  Other  terms  are  employed  of 
more  common  use,  and  requiring  no  ex- 
planation, as  striped,  dotted,  banded,  &c. 

VARIETIES.  In  Botany,  varieties  of 
plants  are  individuals  subordinate  to  spe- 
cies. The  variety  differs  from  the  species 
in  points  of  structure  which  are  de- 
veloped only  under  particular  circum- 
stances, and  which  are  not  essential  to 
the  species.  The  characters  on  which  a 
species  is  founded  should  be  invariable 
under  all  circumstances  ;  the  characters 
of  a  variety  are  induced  by  local  situa- 
tion, by  atmospheric  influence,  by  culti- 
vation, &c. ;  with  all  the  characters  of  the 
species,  the  variety  may  differ  in  a  change 
of  colour,  an  increased  number  of  petals, 
&c.  Varieties  may  be  subdivided,  with 
reference  to  other  non-essential  points, 
constituting  sub-varieties.  The  term  va- 
riety is  similarly  employed  in  Zoology. 

VA'RIOLITE.  A  porphyritic  rock 
consisting  of  an  imperfectly  crystallized 
aggregate  of  felspar  and  quartz. 

VARIX.  A  swollen  vein ;  a  term  em- 
ployed in  Malacology  to  denote  the  strong 
elevated  ridges  which  cross  the  whorls  of 
several  of  the  predaceous  genera,  as  mu- 
rex,  triton,  &c. ;  they  mark  the  progres- 
sive enlargement  of  the  shell,  being  the 
remnants  of  former  apertures,  beyond 
which  the  animal,  when  grown,  forms 
another  aperture. 

VARNISH.  A  substance  made  by 
dissolving  resins  in  alcohol,  or  oil  of  tur- 
pentine, or  in  a  mixture  of  oil  of  turpen- 
tine and  a  drying  oil.  There  are  alcoholic 
or  spirit  varnishes,  volatile-oil  varnishes, 


VED 


VEG 


and  fixed-oil  varnishes.  Lacker,  or  lac- 
quer, is  a  lac  varnish  consisting  of  a 
solution  of  shell-lac  in  alcohol,  and  ap- 
plied to  articles  of  brass,  &c. 

VARNISH-TREES.  A  technical  name 
applied  to  trees  which  exude  liquid 
resins,  naturally  or  in  consequence  of  in- 
cisions. 

VAR'VICITE.  An  ore  of  manganese, 
occurring  massive  at  Hartshill,  in  War- 
wickshire, and  in  pseudo-crystals  at 
Ilfeld. 

VASCULAR  PLANTS  {vasculum,  a 
little  vessel).  A  term  applied  to  the  two 
great  divisions  of  plants  called  Exogens 
and  Endogens,  owing  to  the  high  de- 
velopment of  vascular  tissue  in  these 
plants,  and  in  order  to  distinguish  them 
from  Cellular  or  Cryptogamic  plants, 
in  which  the  tissue  is  principally  cel- 
lular. 

VASCULAR  TISSUE  {vasculum,  a 
little  vessel).  Trachenchyma.  A  tissue 
in  plants,  consisting  of  simple  membra- 
nous  tubes  tapering  to  each  end,  but  often 
ending  abruptly,  either  having  a  fibre 
generated  spirally  in  the  inside,  or  having 
their  walls  marked  by  transverse  bars 
arranged  more  or  less  in  a  spiral  direc- 
tion. There  are  two  principal  kinds  of 
vascular  tissue,  viz.  spiral  vessels  or  tra- 
cheal, and  ducts :  the  former  present  the 
continuous  spiral  fibre,  and  are  capable 
of  unrolling  with  elasticity ;  the  latter 
present  transverse  lines,  rings,  or  bars, 
and  are  incapable  of  unrolliDg  without 
breaking. 

VAU'QUELINITE.  Chromate  of  lead 
and  copper  ;  one  of  the  ores  containing 
chromium,  occurring  massive,  and  in 
minute  crystals  on  quartz,  accompanying 
the  chromate  of  lead,  in  Siberia. 

VECTOR  (veho,  to  carry).  The  car- 
rier ;  a  term  applied,  in  Geometry,  to  a 
radius,  which  is  carried  round  a  centre; 
any  given  point  on  such  a  radius  de- 
scribes a  curve  (See  Radius  Vector).  In 
Astronomy,  a  straight  line  drawn  from 
the  centre  of  a  planet  to  the  centre  of  the 
sun  becomes  a  radius  vector,  and  the 
planet  appears  to  be  carried  by  it  in  its 
orbit  round  the  sun.  In  a  conic  section, 
the  radius  vector  is  a  straight  line  drawn 
from  one  of  the  foci  to  any  point  in  the 
curve. 

VEDA  {vid,  Sansc  to  know).  A  term 
signifying  the  sum  of  all  knowledge  ;  or, 
according  to  another  derivation,  self-ovi- 
dent  knowledge  or  revelation.  The  word 
is,  however,  particularly  applied  to  the 
four  principal  sacred  books  of  the  Hin« 
360 


dus,  viz.  the  Rt'ch,  the  Yajush,  the 
Saman,  and  the  Atharvan'a. 

VEERING  (virer,  French).  Wearing. 
A  nautical  term  for  that  movement  of  a 
ship  by  which,  when  sailing  with  the 
wind  on  either  bow,  she  is  brought,  by 
turning  her  head  to  leeward,  into  a  con- 
trary position,  so  as  to  present  the  other 
bow  to  the  wind,  by  which  means  her 
course  is  reversed. 

VEGA.  A  star  of  the  first  magnitude 
in  the  northern  constellation  Lyra. 

VEGETABLE  jETHIOPS.  A  char- 
coal prepared  by  incinerating  the  fucus 
vesiculosus  in  a  covered  crucible. 

VEGETABLE  IVORY.  A  substance 
sometimes  whiter  and  harder  than  ivory, 
consisting  of  the  seed  of  a  genus  of 
plants  called  Phytelephas,  belonging  to 
the  natural  order  Pandanaceae.  It  is 
commonly  called  tagua  plant;  and  in 
Peru,  celebra  de  negro,  or  negro's  head. 
It  is  extensively  used  for  the  same  pur- 
poses as  ivory,  but  does  not  retain  its 
colour  so  well. 

VEGETABLE  KINGDOM.  In  addi- 
tion to  what  has  been  written  under  the 
article  Botany,  a  sketch  is  here  subjoined 
of  the  connexion  subsisting  between  the 
three  great  kingdoms,  or  divisions  of  na- 
tural bodies.  These  are  represented  each 
as  starting  from  a  common  point ;  and  the 
further  any  group  of  beings  is  from  this 
point,  the  more  are  they  unlike  the 
others. 

ORGANIC    MATTER. 


Vegetable  Kingdom.       Animal  Kingdom. 


Exogenae. 

Gymnospermae. 

Endogenae. 

Rhizanthae. 

Acrogenae. 


Vertebrata. 

Mollusca. 

Articulata, 

Radiata. 

Acrita. 


Indeterminate  Substances. 

Organic  Elements. 

Gases,  Water. 

Metallic  Oxides. 

Metals 

Mineral   Kingdom. 

INORGANIC    MATTER. 

VEGETABLE  SOIL.  The  thin  ex 
ternal  crust  of  the  earth  in  which  plants 
grow,  composed  of  fragments  of  mine- 
rals, vegetables,  and  animals,  reduced  to 
a  great  degree  of  tenuity. 

VEGETABLE  SULPHUR.  Witch- 
meal.  A  powder  procured  from  the  theca 
of  the  lycopodium  clavatum,  or  common 


VEI 


VEL 


club-moss.     It  is  highly   inflammable, 
and  is  used  for  pyrotechnical  purposes. 

VEGETABLE  WAX.  A  wax-like  sub- 
stance procured  from  several  species  of 
Myrica,  one  species  of  which  {gale),  from 
the  uses  to  which  this  substance  has  been 
devoted,  has  been  named  the  Tallow- 
shrub  or  Candleberry-tree.  The  wax  is 
found,  in  some  cases,  on  the  berries,  in 
others  on  the  cones  or  catkins.  Another 
remarkable  plant  of  this  kind  is  the  Ce- 
roxijlon  andicola,  a  Wax  Palm  of  the 
American  Spaniards. 

VEGETATION,  SALINE.  A  kind  of 
crystalline  film  which  shoots  up  spon- 
taneously from  the  edges  of  a  solution  of 
crystallizable  matter,  as  salt,  camphor, 
&c. 

VEGETO  -  ALKALIES.  Alkaloids. 
A  class  of  bodies  obtained  from  the  vege- 
table kingdom,  containing  nitrogen,  hav- 
ing the  properties  of  the  basic  or  metallic 
oxides,  and  forming  salts  with  acids.  Of 
this  class  are  quinine,  strychnine,  vera- 
trine,  &c. 

VEGETO-SULPHURIC  ACID.  An 
acid  procured  by  treating  ligneous  fibre 
with  sulphuric  acid. 

VEINS,  MINERAL.  Cracks  or  fis- 
sures in  rocks  filled  up  by  substances 
different  from  the  rock,  which  may  be 
either  earthy  or  metallic.  Veins  are 
sometimes  many  yards  wide ;  and  they 
ramify  or  branch  off  into  innumerable 
smaller  parts,  often  as  slender  as  threads, 
like  the  veins  of  an  animal.  Inconsider- 
able veins,  which  diverge  from  the  prin- 
cipal, are  called  slips;  and  those  masses 
of  ore  which  are  of  considerable  magni- 
tude, but  of  no  great  length,  are  called 
bellies,  or  stockworks. 

M.  Came  characterizes  eight  succes- 
sive groups  of  veins  and  slides  in  Corn- 
wall. The  oldest  are  tin  veins  (lodes), 
underlying  (dipping)  to  the  north, 
ranging  nearly  e.  and  w.  by  compass. 
The  second  class  consists  of  tin  veins, 
underlying  to  the  south,  ranging  e.  and  w. 
nearly  (by  compass).  The  third  includes 
east  and  west  copper  veins.  The  fourth 
are  diagonal  (or  contra)  veins,  ranging 
N.w.  and  s.e.,  and  yield  copper.  The 
fifth  includes  cross  courses,  ranging  n.nw. 
and  s.se.,  and  rarely  yielding  metal,  ex- 
cept lead.  A  sixth  group  includes  ■  cross 
flukans'  (clay  veins),  ranging  nearly  n. 
and  s.  An  eighth  includes  '  the  slides,' 
which  are  formed  of  soft  clay,  and  cut 
through  all  the  others. 

VEINS  OF  PLANTS.    The  ramifica- 
tions of  the  petiole  among  the  cellular 
361 


tissue  of  the  leaf  are  called  veins,  and 
the  manner  of  their  distribution  is  termed 
venation. 

1.  The  principal  vein,  or  that  which 
forms  a  continuation  of  the  petiole  and  the 
axis  of  the  leaf,  is  called  the  midrib  or 
costa ;  if  other  veins  similar  to  the  mid- 
rib pass  from  the  base  to  the  apex  of  the 
leaf,  such  veins  have  been  called,  though 
incorrectly,  nerves,  and  a  leaf  with  such 
a  distribution  of  veins  has  been  called  a 
nerved  leaf. 

2.  A  leaf  is  said  to  be  three,  ox  five,  or 
otherwise  nerved,  if  the  so-called  nerves 
all  proceed  from  the  base  of  the  lamina ; 
it  is  also  said  to  be  triple,  quintuple,  &c. 
nerved.  If  the  veins  diverge  from  the 
midrib  towards  the  margin,  ramifying  as 
they  proceed,  such  a  leaf  is  called  a 
venous  or  reticulated  leaf. 

3.  Dr.  Lindley  adopts  the  following 
terms  :— 1.  The  largest  veins  given  off 
from  the  midrib  on  each  side,  are  the 
primary  veins ;  each  of  these  forms  a 
curve,  and  anastomoses  with  the  back  of 
the  next  primary;  the  curved  portion 
being  called  the  curved  vein.  2.  Between 
the  curved  vein  and  the  margin,  other 
veins,  proceeding  from  the  curved  veins, 
with  the  same  curved  direction,  and  of 
the  same  magnitude,  occasionally  inter- 
vene :  these  may  be  distinguished  as 
external  veins.  3.  The  margin  itself  and 
these  last  are  connected  by  a  fine  net- 
work of  minute  veins,  which  may  be 
called  marginal  veinlets.  4.  From  the 
midrib  are  generally  produced,  at  right 
angles  with  it,  and  alternate  with  the 
primary  veins,  smaller  veins,  which  may 
be  called  costal  veins.  5.  The  primary 
veins  are  themselves  connected  by  fine 
veins,  which  anastomose  in  the  area  be- 
tween them  ;  these  veins,  when  they  im- 
mediately leave  the  primary  veins,  are 
proper  veinlets,  and,  where  they  anasto- 
mose, common  veinlets.  6.  The  area  of 
parenchyma,  lying  between  two  or  more 
veins  or  veinlets,  is  called  intervenium. 

VELO'CITY  (velox,  quick).  The  velo- 
city of  a  body  is  the  rate  of  its  motion,  or 
the  degree  of  quickness  with  which  it  is 
moving.  The  velocity  of  a  body  is  uni- 
form, when  it  moves  through  equal 
spaces  in  equal  times,  and  it  is  then 
measured  by  the  space  described  in  a 
certain  unit  of  time,  as  a  second ;  when 
the  velocity  is  variable,  it  is  measured  by 
the  space  which  would  be  described  in 
the  said  time  if  the  motion  were  con- 
tinued uniform  for  that  time. 

1.  Velocity,  absolute  and  relative.   The 


VEN 


VEN 


velocity  of  a  body  is  called  absolute,  if  we 
consider  its  motion  in  space,  without  any 
reference  to  that  of  other  bodies.  It  is 
termed  relative,  when  compared  with 
that  of  another  body  which  is  itself  in 
motion.  If  two  carriages  go  along  the 
same  road  in  the  same  direction,  their 
relative  velocities  will  be  the  difference 
of  their  absolute  velocities;  if  in  oppo- 
site directions,  the  same.     See  Motion. 

2.  Velocities,  parallelogram  of.  A  pro- 
position very  nearly  analogous  to  the 
'parallelogram  of  forces,'  employed  for 
finding  the  resultant  of  two  velocities. 
Thus,  "  if  two  velocities,  with  which  a 
particle  is  simultaneously  animated,  be 
represented  in  direction  and  magnitude 
by  two  straight  lines  drawn  from  the 
particle,  the  resultant  velocity  of  the 
particle  will  be  represented  in  direction 
and  magnitude  by  the  diagonal  of  the 
parallelogram  described  upon  those  two 
straight  lines." 

3.  Velocity,  resolution  of.  It  follows 
from  the  proposition  just  stated,  that,  if 
a  particle  be  moving  with  a  velocity  v  in 
a  direction  making  an  angle  9  with  a 
given  line,  we  may  conceive  the  particle 
to  be  animated  by  two  velocities,  v  cos  0 
in  the  direction  parallel  to  the  given  line, 
and  v  sin  $  in  the  direction  perpendicular 
to  it.     This  is  called  resolving  a  velocity. 

VELUM.  Literally,  a  veil;  hence 
applied  to  a  horizontal  membrane  con- 
necting the  margin  of  the  pileus  of  a 
fungus  with  the  stipes.  When  it  is 
adnate  with  the  surface  of  the  pileus,  it 
is  a.  velum  universale;  when  it  extends 
only  from  the  margin  of  the  pileus  to  the 
stipes,  it  is  a  velum  partiale. 

VENATION  OF  LEAVES.  A  term 
denoting  the  manner  in  which  the  veins 
are  distributed  among  the  cellular  tissue 
of  the  leaf.  Writers  differ  much  on  this 
point  of  nomenclature :  the  following 
arrangement  is  taken  from  Dr.  Lindley's 
"Introduction  to  Botany."  Leaves  are 
called, — 

1.  Veinless,  when  no  veins  at  all  are 
formed,  except  a  slight  approach  to  a 
midrib,  as  in  mosses,  fuci,  fee.,  and  the 
lowest  tribes  of  foliaceous  plants.  Under 
this  head,  De  Candolle  has  his  folia  nul- 
linervia,  in  which  there  is  not  even  a 
trace  of  a  midrib,  as  in  ulva ;  and  folia 
falsinervia,  in  which  a  trace  of  a  midrib 
is  perceptible. 

2.  Equal-veined,  when  the  midrib  is 
perfectly  formed,  and  the  veins  are  all  of 
equal  size,  as  in  ferns.  These  are  inter- 
mediate between  those  without  veins  and 

362 


those  in  which  "primary  "  veins  are  first 
apparent.  The  veins  are  equal  in  power 
to  the  "proper  veinlets"  of  leaves  of  a 
higher  class.     See  Veins  of  plants. 

3.  Straight-veined,  when  the  veins  are 
entirely  primary,  generally  very  much 
attenuated,  and  arising  from  towards  the 
base  of  the  midrib,  with  which  they  lie 
nearly  parallel ;  they  are  connected  by 
"proper  veinlets;"  but  there  are  no 
"common  veinlets."  The  leaves  of 
grasses  and  of  palms  and  orchidaceous 
plants  are  of  this  nature. 

4.  Curve-veined,  a  modification  of  the 
last  form,  in  which  the  primary  veins  are 
also  parallel,  simple,  and  connected  by 
unbranched  "proper  veinlets;"  do  not 
pass  from  near  the  base  to  the  apex  of 
the  leaf,  but  diverge  from  the  midrib 
along  its  whole  length,  and  lose  them- 
selves in  the  margin.  It  is  common  in 
Zingiberaceae.  The  straight-veined  and 
curve-veined  leaves  are  referred  by  De 
Candolle  to  modifications  of  the  petiole. 

5.  Netted,  when  all  the  veins  of  a  com- 
pletely developed  leaf  are  present,  ar- 
ranged as  described  under  the  article 
Veins  of  plants,  without  any  peculiar 
combination  of  any  class  of  veins.§  This 
is  the  common  form  of  the  leaves  of 
dicotyledons,  as  of  the  lilac,  the  rose,  &c. 
This  is  the  folium  retinervium  of  De  Can- 
dolle. 

6.  Ribbed,  when  three  or  more  mid- 
ribs proceed  from  the  base,  to  the  apex  of 
the  leaf,  and  are  connected  by  branching 
primary  veins  of  the  form  and  magni- 
tude of  proper  veinlets,  as  in  melastoma. 
This  must  not  be  confounded  with  the 
straight-veined  leaf,  from  which  it  may  in 
all  cases  of  doubt  be  distinguished  by  the 
ramified  veins  which  connect  the  ribs. 
If  a  ribbed  leaf  has  three  ribs  springing 
from  the  base,  it  is  said  to  be  three- 
ribbed;  if  five,  five-ribbed ;  and  so  on. 
But  if  the  ribs  do  not  proceed  exactly 
from  the  base,  but  from  a  little  above  it, 
the  leaf  is  then  said  to  be  triple-ribbed,  as 
in  helianthus. 

7.  Falsely  ribbed,  when  the  "  curved  " 
and  "external  veins,"  both  or  either,  in  a 
netted  leaf,  become  confluent  into  a  line 
parallel  with  the  margin,  as  in  all  myr- 
taceous  plants.  This  has  not  been  before 
distinguished. 

8.  Radiating,  when  several  ribs  radiate 
from  the  base  of  a  netted  leaf  to  its  cir- 
cumference, as  in  lobed  leaves.  To  this 
head  are  referred  the  pedalinerved,  palmi- 
nerved,  and  peltinerved  leaves  of  De  Can- 
dolle ;  the  differences  of  which  do  not 


VEN 


VER 


arise  out  of  any  peculiarity  in  the  vena- 
tion, but  from  the  particular  form  of  the 
leaves  themselves. 

9.  Feather-veined,  in  which  the  pri- 
mary veins  of  a  netted  leaf  pass  in  a 
right  line  from  the  midrib  to  the  margin, 
as  in  castanea.  This  has  the  same  rela- 
tion to  the  radiating  leaf  as  the  curve- 
veined  bears  to  the  straight-veined.  It 
is  the  folium  penninervium  of  De  Can- 
dolle. 

10.  Hidden-veined,  when  the  veins  are 
hidden  from  view  by  the  parenchyma 
being  in  excess,  as  in  hoya.  Such  a  leaf 
is  often  inaccurately  called  veinless.  De 
Candolle  calls  a  leaf  of  this  nature,  in 
which  the  veins  are  dispersed  through  a 
large  mass  of  parenchyma,  as  in  mesem- 
bryanthemum,  folium  vaginervium. 

11.  The  direction  which  the  primary 
veins  take  when  they  diverge  from  the 
midrib,  can  be  denoted  by  measuring  the 
angle  formed  by  the  midrib  and  the  di- 
verging vein,  and  can  be  stated  either 
in  distinct  words  or  by  applying  the 
following  terms  :  —  thus,  if  the  angle 
formed  by  the  divergence  is  between  10° 
and  20°,  the  vein  may  be  said  to  be  nearly 
parallel  (subparallela) ;  if  between  20° 
and  40°,  diverging ;  between  40°  and  60°, 
spreading ;  between  60°  and  80°,  divari- 
cating; between  80°  and  90c  right  angled ; 
between  90°  and  120°,  oblique;  beyond 
120°,  reflexed  (retroflexa). 

VENE'RIDiE.  A  family  of  macro- 
trachian  bivalves,  named  from  the  genus 
Venus,  and  characterized  by  the  mode- 
rate length  of  the  two  siphons,  which  are 
sometimes  united. 

VENT-PEG.  The  pressure  of  the 
atmosphere,  transmitted  as  it  is  in  all 
directions  with  a  weight  of  about  fifteen 
pounds  on  the  square  inch,  prevents  the 
flow  of  liquids  from  a  small  aperture  of 
a  vessel,  unless  the  pressure  be  admitted 
to  the  surface  of  the  liquid.  The  vent- 
peg  is,  therefore,  raised  in  order  to  ad- 
mit the  air  to  the  surface  of  a  liquid 
which  is  to  be  drawn  off  from  a  closed 
vessel. 

VENTRAL  [venter,  the  belly).  A 
term  applied,  in  Botany,  to  that  suture  of 
the  legume  to  which  the  seeds  are  at- 
tached, the  opposite  being  called  the  dor- 
sal suture. 

VENTRICOSE  (venter,  the  belly). 
Bellying ;  swelling  unequally  on  one 
side ;  as  the  corolla  of  many  labiate  and 
personate  plants. 

VENTRICULITES.  A  genus  of 
spongoid  zoophytes   found   in  the   cre- 


taceous system,  having  their  porous 
tissue  penetrated  by  distinct  ventricles 
or  foramina,  sometimes  of  large  dimen- 
sions, and  with  a  certain  degree  of  regu- 
larity. 

VENUS.  The  most  beautiful  of  all 
the  stars.  Her  mean  distance  from  the 
sun  is  seventy  millions  of  miles ;  her 
apparent  diameter  varies  from  30"  to 
184".  Her  rotation  on  her  axis  takes 
place  in  23d.  21'  19",  and  the  period  of  her 
revolution  round  the  sun  is  224d.  16h  49'. 
When  Venus  is  in  that  part  of  her  orbit 
which  gives  her  the  appearance  of  being 
west  of  the  sun,  she  rises  before  him, 
and  is  then  called  the  morning  star ;  and 
when  she  appears  east  of  the  sun,  she  is 
behind  him  in  her  course,  and  is  then 
called  the  evening  star. 

VERA'S  CORD-PUMP.  An  endless 
cord,  running  round  two  wheels,  descends 
below  the  surface  of  the  water,  which  it 
raises  by  means  of  the  adhesion  subsist- 
ing between  the  liquid  and  the  cord,  to 
which  a  rapid  motion  is  imparted  by  the 
upper  wheel.  On  this  effect  of  adhesion 
depend  writing  with  ink,  colour  drawing, 
the  smearing  of  metals,  especially  iron, 
with  oil  or  grease,  to  protect  them  from 
rust. 

VERA'TRIC  ACID.  An  acid  with 
which  the  alkali  veratria  is  combined  in 
cebadilla,  the  seed  of  the  helonias  offi- 
cinalis. 

VERB  {verbum,  a  word).  That  part  of 
speech  which  expresses  the  action  or 
being  of  a  thing,  and  which  is  usually 
the  principal  word  of  a  sentence.  A  verb 
is  called  active-transitive,  when  it  ex- 
presses an  action  exerted  upon  some  ob- 
ject; active-intransitive,  when  its  action  is 
not  communicated  to  any  object ;  passive, 
when  it  represents  its  subject  or  nomina- 
tive as  being  acted  upon  ;  neuter,  when  it 
expresses  a  state  of  existence  without 
action  or  passion. 

Verbs,  auxiliary.  Verbs  which,  though 
they  originally  expressed  motions  of 
action,  only  express  relations  of  action 
when  considered  as  auxiliary  verbs,  and 
are  accordingly  employed,  in  connexion 
with  other  verbs,  to  give  them  certain 
relations  called  by  grammarians  tense, 
mood,  and  voice. 

VERBAL  and  REAL  QUESTIONS. 
"  Sometimes  the  Question  turns  on  the 
meaning  and  extent  of  the  terms  em- 
ployed ;  sometimes,  on  the  things  signi- 
fied by  them.  If  it  be  made  to  appear, 
therefore,  that  the  opposite  sides  of  a 
certain  Question  may  be  held  by  persons 
R2 


VER 


VER 


not  differing  in  their  opinion  of  the  matter 
in  hand,  then  that  Question  may  be  pro- 
nounced Verbal ;  as  depending  on  the 
different  senses  in  which  they  respec- 
tively employ  the  terms.  If,  on  the  con- 
trary, it  appears  that  they  employ  the 
terms  in  the  same  sense,  but  still  differ 
as  to  the  application  of  one  of  them  to 
the  other,  tben it  maybe  pronounced  that 
the  Question  is  Real;— that  they  dif- 
fer as  to  the  opinions  they  hold  of  the 
things  in  Question."  —  Whately. 

VERBENA'CE^E.  The  Verbena  or 
Vervain  tribe  of  dicotyledonous  plants. 
Trees  or  shrubs,  sometimes  herbs,  with 
leaves  opposite  ;  calyx  tubular ;  corolla 
irregular ;  stamens  didynamous,  occa- 
sionally 2 ;  fruit  consisting  of  2  or  4  nu- 
cules in  a  state  of  adhesion;  seeds  ex- 
albuminous. 

VERD  ANTIQUE.  A  beautiful  mot- 
tled green  marble,  an  aggregate  of  marble 
and  serpentine. 

VERDIC  ACID.  An  acid  obtained 
from  the  root  of  the  scabiosa  succisa  and 
other  plants,  and  named  from  its  pro- 
perty of  becoming  green  on  exposure  to 
the  air,  owing  to  the  absorption  of 
oxygen. 

VE'RDIGRIS  (verde-gris).  A  sub- 
acetate  of  copper,  formed  by  placing 
plates  of  the  metal  in  contact  with  the 
fermenting  marc  of  the  grape,  or  with 
cloth  dipped  in  vinegar.  The  green  salt  is 
found  in  commerce  under  the  improper 
name  of  distilled  verdigris.  A  spurious 
kind  is  sold  under  the  name  of  English 
verdigris,  consisting  of  sulphate  of  copper 
and  acetate  of  lead. 

VE'RDITER.  A  blue  pigment,  pro- 
cured by  adding  chalk  or  whiting  to  a 
solution  of  copper  in  aquafortis. 

VERJUICE  (verjus,  Fr.).  A  kind  of 
harsh  vinegar,  made  of  the  expressed 
juice  of  the  wild  apple  or  crab,  which 
has  undergone  the  vinous  fermentation. 
The  French  give  this  name  to  unripe 
grapes,  and  to  the  sour  liquor  obtained 
from  them. 

VERMI'CULITE.  A  silicate  of  mag- 
nesia and  iron,  described  as  composed  of 
micaceous-looking  plates  cemented  toge- 
ther by  a  whitish  matter. 

VERMILION.  A  red  pigment,  con- 
sisting of  powdered  cinnabar,  or  the 
red  sulphuret  of  mercury.  This  sub- 
stance, if  heated  till  sulphur  begins  to 
sublime  from  it,  and  then  suddenly 
thrown  into  cold  water,  becomes  black ; 
although,  if  allowed  to  cool  slowly,  it 
remains  red.  Yet  it  is  of  the  same  com- 
364 


position  exactly  in  the  black  and  red 
states. 

VERNAL  EQUINOX.  The  time 
when  the  sun  enters  the  first  point  of 
Aries,  or  the  ascending  point  of  the 
ecliptic,  is  the  vernal  equinox  to  those 
who  live  in  the  northern  hemisphere, 
while  the  first  point  of  Libra  is  the  same 
to  those  in  the  southern. 

VERNA'TION  {vernus,  belonging  to 
the  Spring).  Gemmation.  A  botanical 
term  denoting  the  manner  in  which  the 
leaves  of  plants  are  arranged  in  the  un- 
expanded  or  bud  state.  The  ideas  ex- 
pressing these  modifications  are  essen- 
tially the  same  as  those  applied  to  the 
parts  of  the  flower  in  the  same  state,  to 
which  the  term  ^Estivation  on  Prceflora- 
tion  is  devoted.  The  Vernation  or  iEsti- 
vation  of  plants  is  said  to  be, — 

1.  Involute,  when  the  edges  of  the 
leaves  are  rolled  inwards  spirally  on  each 
side,  as  the  leaf  of  the  apple. 

2.  Revolule,  when  the  edges  are  rolled 
backwards  spirally  on  each  side,  as  the 
leaf  of  rosemary ;  or,  in  other  words, 
when  two  conduplicate  leaves  clasp  each 
other. 

3.  Obvolute,  when  the  margins  of  one 
leaf  alternately  overlap  those  of  the  leaf 
which  is  opposite  to  it. 

4.  Convolute,  when  one  leaf  is  wholly 
rolled  up  in  another,  as  the  petals  of 
wallflower. 

5.  Supervolute,  when  one  edge  is  rolled 
inwards,  and  is  enveloped  by  the  oppo- 
site edge  rolled  in  an  opposite  direction, 
as  the  leaves  of  apricot. 

6.  Induplicate,  when  the  margins  are 
bent  abruptly  inwards,  and  the  external 
face  of  these  edges  are  applied  to  each 
other  without  any  twisting,  as  in  the 
flowers  of  some  species  of  clematis. 

7.  Conduplicate,  when  the  sides  are 
applied  parallelly  to  the  faces  of  each 
other,  as  in  the  leaves  of  the  cherry. 

8.  Plaited,  when  the  leaves  are  folded 
lengthwise,  like  the  plaits  of  a  closed  fan, 
as  in  the  vine  and  many  palms. 

9.  Replicate,  when  the  upper  part  of 
the  leaf  is  curved  back  and  applied  to 
the  lower,  as  in  aconite. 

10.  Curvative,  when  the  margins  are 
slightly  curved,  either  backwards  or  for- 
wards, without  any  sensible  twisting. 

11.  Wrinkled,  when  the  parts  are  folded 
up  irregularly  in  every  direction,  as  the 
petals  of  the  poppy. 

12.  Imbricated,  when  the  parts  overlap 
one  another  parallelly  at  the  margins, 
without  any  involution. 


VER 


VER 


13.  Eguitant,  where  the  parts  overlap 
each  other  parallelly  and  entirely,  without 
any  revolution,  as  the  leaves  of  iris. 

14.  Reclinate,  when  the  parts  are  bent 
down  upon  their  stalk. 

15.  Circinate,  when  the  parts  are  rolled 
spirally  downwards,  as  the  fronds  of 
ferns. 

16.  Falvate,  when  the  parts  are  applied 
to  each  other  by  the  margins  only,  as  the 
petals  of  umbelliferous  plants,  the  valves 
of  a  capsule,  &c. 

17.  Quincuncial,  when  the  parts  are 
five  in  number,  of  which  two  are  exterior, 
two  interior,  while  the  fifth  covers  the 
interior  with  one  margin,  and  has  its 
other  margin  covered  by  the  exterior,  as 
in'  the  rose. 

18.  Contorted,  when  each  part  is 
oblique  in  figure,  and  overlaps  its  neigh- 
bour by  one  margin,  its  other  margin 
being,  in  like  manner,  overlapped  by  that 
which  stands  next  to  it,  as  in  apocy- 
naceae. 

19.  Twisted,  the  same  as  contorted, 
except  that  there  is  no  obliquity  in  the 
form  or  insertion  of  the  pieces,  as  in  the 
petals  of  oxalis. 

20.  Alternative,  when,  the  pieces  being 
in  two  rows,  the  inner  is  covered  by  the 
outer  in  such  a  way  that  each  of  the  ex- 
terior rows  overlaps  half  of  two  of  the 
interior,  as  in  liliaceous  plants. 

21.  Vexillary,  when  one  piece  is  much 
larger  than  the  others,  and  is  folded  over 
them,  they  being  arranged  face  to  face, 
as  in  papilionaceous  flowers.  See  Vex- 
illum. 

22.  Cochlear,  when  one  piece,  being 
larger  than  the  others,  and  hollowed  out 
like  a  helmet  or  bowl,  covers  all  the 
others,  as  in  aconite,  some  species  of 
personate  plants,  &c. 

VERNIER.  A  small  moveable  scale, 
running  parallel  with  the  fixed  scale  of 
a  quadrant  or  other  instrument,  and 
having  the  effect  of  subdividing  the 
divisions  of  that  instrument  into  more 
minute  parts.  Its  name  is  derived  from 
that  of  its  inventor.     See  Nonius. 

Vernier,  chromatic.  An  instrument 
invented  and  so  named  by  Dr,  Brewster, 
and  employed  for  measuring,  by  com- 
parison, very  minute  variations  of  tints. 

VERRU'CjE  {verruca,  a  wart).  Warts, 
or  sessile  glands,  produced  upon  various 
parts  of  plants,  and  extremely  variable 
in  figure.  They  are  the  cellular  glands  of 
Mirbel.  As  they  occur  on  the  skin  of 
the  seed,  they  are  the  seminal  spongioles 
of  De  Candolle. 
365 


VE'RSATILE  (versatilis,  that  turns 
easily).  Oscillating;  adhering  slightly  by 
the  middle,  so  that  the  two  halves  are 
nearly  balanced,  and  swing  backwards 
and  forwards;  a  term  applied  to  the 
anthers  of  plants,  when  they  are  attached 
to  the  filament  by  a  single  point  of  the 
connective,  as  in  all  true  grasses. 

VERSED  AND  SUVERSED  SINE. 
The  versed  sine  of  an  arc  is  that  portion 
of  the  radius  intercepted  between  the 
sine  and  the  extremity  of  the  arc.  The 
suversed,  or  supplemental  versed,  sine  is 
the  difference  between  the  versed  sine 
and  the  diameter. 

Etymology.  M  The  term  sine  (the  Latin 
word  sinus  meaning  the  bosom)  has  been 
the  object  of  much  discussion.  It  was 
at  one  time  looked  on  as  a  barbarism 
from  the  Arabic  ;  and  some  endeavoured 
to  substitute  semissis  inscriptce,  the  half 
of  the  chord,  for  it.  Others  again  thought 
that  it  was  a  corruption  of  S.  Ins.,  the 
abbreviation  of  the  above.  Dr.  Hutton 
asserts  that  the  Arabic  word  jeib,  which 
is  used  for  the  trigonometrical  sine  in 
that  language,  also  means  the  bosom  in 
common  language ;  and  we  have  been 
told  that  this  is  correct :  if  so,  the  Latin 
sinus  is  only  the  literal  translation  of  the 
Arabic.  The  arc  representing  a  bow 
(from  which  it  gets  its  name),  half  of  the 
string,  which  represents  the  sine  of  half 
the  arc,  would  come  against  the  breast  of 
the  archer.  The  versed  sine  (sinus  ver- 
sus, or  turned  sine)  was  called  the  sagitta, 
or  arrow." — Pen.  Cycl. 

VERTEBRA'TA  (vertebra,  a  joint  of 
the  back-bone).  A  large  division  of  the 
Animal  Kingdom,  including  all  those 
species  which  are  furnished  with  a  back- 
bone, or  vertebral  column,  as  the  mam- 
malia, birds,  reptiles,  and  fishes.  These 
are  the  Myelencephala  of  Owen,  the  Spi- 
nicerebrata  of  Grant. 

VERTEX.  Literally,  the  top  or  sum- 
mit of  any  figure.  In  Astronomy,  it  de- 
notes that  point  in  the  heavens  which  is 
directly  over  our  heads,  called  the  zenith. 
In  Geometry,  it  is  the  apex,  or  upper 
point,  of  a  triangle.  In  conic  sections,  it 
is  the  point  through  which  the  genera- 
ting line  of  the  conical  surface  always 
passes.  The  vertex  of  a  curve  is  the 
point  in  which  the  diameter  meets  the 
curve. 

VERTICAL  (vertex,  the  top).  Per- 
pendicular ;  being  at  right  angles  to  any 
body.  A  vertical  circle,  in  Astronomy, 
is  a  great  circle  perpendicular  to  the 
horizon,  and  passing  through  the  zenith 
R3 


VES 


VES 


and  nadir  of  any  place.  A  vertical  line 
has  the  same  meaning.  A  vertical 
plane,  in  conies,  denotes  a  plane  passing 
through  the  vertex,  and  parallel  to  the 
plane  of  the  section. 

VERTICAL  CIRCLES.  This  name 
is  applied,  in  Nautical  Astronomy,  to 
great  circles  drawn  on  the  hollow  sphere, 
passing  through  the  zenith  of  any  place. 
That  particular  vertical  circle  which 
passes  through  the  east  and  west  points, 
is  called  the  prime  vertical;  the  angle 
contained  between  a  vertical  circle  pass- 
ing through  a  heavenly  body  and  the 
celestial  meridian  opposite  to  a  place,  is 
called  its  azimuth. 

VERTICILLA'STER  (verticillus,  a 
whorl).  A  botanical  term  applied  by 
HofFmansegg  to  the  cyme  when  reduced 
to  a  very  few  flowers.  It  constitutes  the 
normal  form  of  inflorescence  of  the  La- 
biatae,  or  Mint  tribe,  in  which  two  verti- 
cillastri  are  situated  opposite  to  each 
other  in  the  axils  of  opposite  leaves.  By 
Linnaeus,  the  union  of  two  such  verti- 
cillastri  was  called  a  verticillus,  or  whorl ; 
and  by  others,  with  more  accuracy,  a 
verticillus  spurius,  or  false  whorl.  By 
Link,  this  form  of  inflorescence  is  called 
a  thyrsula. 

VERTICI'LLUS  (verto,  to  turn).  Lite- 
rally, a  little  whern,  a  whorl,  an  axis,  or 
spindle.  This  term  is  applied,  in  Botany, 
to  that  arrangement  of  leaves  upon  the 
stem,  in  which  more  than  two  of  them 
are  opposite  to  one  another,  or  are  on  the 
same  plane,  as  in  Galium.  The  natural 
order  Galiaceae  has,  in  fact,  been  named 
Stellatce,  from  the  stellate  or  whorled 
arrangement  of  the  leaves. 

"VESICLE  (vesicula,  dim.  of  vesica,  a 
bladder).  A  small,  circular,  inclosed 
space,  like  that  contained  by  a  little 
bladder.  Hence,  the  term  vesicular  tissue 
is  applied  to  one  of  the  elementary 
tissues  of  plants,  generally  consisting  of 
little  bladders  or  vesicles  of  various 
figures,  adhering  together  in  masses. 
This  is  also  called  cellular  and  utricular 
tissue. 

VESICULA  AMNIOS.  Vesicula  col- 
liquamenti.  The  name  given  by  Mal- 
pighi  to  the  quintine,  or  fifth  integument 
occasionally  found  in  the  ovule  of  plants. 
This  is  called  by  other  writers,  sac  of  the 
embryo,  additional  membrane,  &c.  A 
very  delicate  thread,  called  the  suspensor, 
descends  from  the  summit  of  the  ovule 
into  the  quintine,  and  bears  at  its  ex- 
tremity a  globule  which  is  the  nascent 
embryo. 
366 


VESPERTILIO'NID-E.  The  Bat 
tribe;  a  family  of  insectivorous  Cheiropte- 
rans,  characterized  by  peculiarities  of  the 
nasal  appendages.  In  the  Rhinolophince, 
or  Horse-shoe  bats,  the  nasal  appendages 
are  complicated  and  membranaceous ; 
in  the  Phyllostomince,  or  true  Leaf-nosed 
bats,  the  appendage  is  simple,  fleshy, 
solitary  or  double  ;  in  the  Pteropinet,  or 
Simple-nosed  bats,  in  the  Noctilionince, 
or  Bull-dog  bats,  and  in  the  Vesper- 
tilionince,  or  True  bats,  there  is  no  nasal 
appendage  at  all. 

VE'SPIMi  (vespa,  a  wasp).  The 
Wasp  tribe ;  a  family  of  hymenopterous 
insects,  distinguished  from  all  other  spe- 
cies of  the  order  by  having  their  wings 
folded,  when  at  rest,  through  their  entire 
length. 

VESSELS,  MILK,  AND  TURPEN- 
TINE. Vasa  propria.  These  names 
were  given  by  Grew  to  certain  cavities 
in  plants,  formed  by  expansion  of  the 
simple  "intercellular  spaces,"  and  filled 
with  the  peculiar  juices  of  the  plant,  as 
with  milk  in  the  poppy,  with  turpentine 
in  terebinthus,  &c.  These  are  the  acci- 
dental reservoirs  and  the  ccecal  reservoirs 
of  De  Candolle.     See  Vittcc. 

VESSELS,  STRANGULATED.  Vasa 
moniliformia,  vel  vermiformia.  A  variety 
of  vessels  found  in  plants,  characterized 
by  a  moniliform,  or  necklace-like,  appear- 
ance, occasioned  by  irregular  compres- 
sion, or  strangulation,  when  growing  in 
knots  or  parts  which  are  subject  to  an 
interrupted  mode  of  development.  By 
the  French,  these  vessels  are  termed 
vaisseaux  en  chapelet  or  etrangles.  They 
are  considered  to  be  young  spiral  vessels, 
which,  instead  of  lengthening,  grow  toge- 
ther by  their  ends. 

VESSELS,  VITAL.  Vasa  opophora. 
A  peculiar  form  of  vessels  in  plants,  con- 
sisting of  branched  anastomosing  tubes, 
lying  in  no  definite  position  with  regard 
to  other  tissue,  said  to  be  contractile, 
;  though  destitute  of  valves  in  their  in- 
terior. They  occur  in  the  milky  cicho- 
raceous  plants,  in  the  root  of  dandelion, 
&c.  The  larger  trunks  were  called  by 
Schultz  vasa  expansa ;  the  fine  ramifica- 
tions, vasa  contracta.  From  their  con- 
taining a  peculiar  liquid,  called  latex, 
they  have  been  termed  laticiferous  tissue, 
and,  more  recently,  cinenchyma. 

VESTA.  A  telescopic  planet,  situated 
in  the  solar  system  between  Mars  and 
Jupiter,  discovered  by  Dr.  Olbers,  of 
Bremen,  in  1807.  She  describes  her  orbit 
in  three  years,  sixty-six  days,  four  hours. 


VIB 


VIN 


She  is  thought  to  be  225  millions  of 
miles  distant  from  the  sun. 

VESU'VIAN  or  FDOCRASE.  A 
stone,  generally  of  a  reddish-brown  co- 
lour, similar  in  appearance  to  common 
garnet.  It  is  found  crystallized  among 
substances  thrown  out  by  volcanoes,  and, 
as  its  name  indicates,  particularly  by 
Mount  Vesuvius.  The  rare  blue  variety 
is  found  at  Sonneland,  in  Tellemark  in 
Norway.  At  Naples  it  is  cut  into  ring- 
stones. 

VEXI'LLUM  (dim.  of  velum,  a  veil). 
A  standard  or  small  banner ;  a  term  ap- 
plied to  the  upper  petal  of  a  papilionace- 
ous corolla,  from  its  erect  and  expanded 
state.  For  the  use  of  the  term  vexillary, 
see  Vernation. 

VIBRATING  SURFACES.  The  phe- 
nomena of  the  production  of  figures  by 
strewing  sand  on  vibrating  surfaces,  com- 
monly called  acoustic  figures,  have  been 
noticed  under  the  terms  "  Sonorous 
Figures"  and  "Nodal  Lines."  Mr. 
Wheatstone  shows  that  all  the  figures  of 
these  vibrating  surfaces  are  the  resultants 
of  very  simple  modes  of  oscillation,  oc- 
curring isochronously,  and  superposed 
upon  one  another;  the  resultant  figure 
varying  with  the  component  modes  of 
the  vibration,  the  number  of  the  super- 
positions, and  the  angles  at  which  they 
are  superposed.  When  the  vibrations  of 
the  superposed  modes  are  unequal  in 
intensity,  there  is  formed  a  figure  inter- 
mediate between  the  perfect  resultant 
and  one  of  its  compounds :  these  figures 
are  called  imperfect  resultants. 

VIBRATION  (vibro,  to  quiver).  Os- 
cillation. A  term  applied  to  those  mo- 
tions of  a  body,  by  which,  when  its  con- 
stituent particles  have  been  disturbed 
from  their  equilibriums,  they  return  to  a 
state  of  repose.  This  is  effected  by  the 
particles  alternately  approaching  the  posi- 
tion of  rest  and  receding  from  it,  until, 
after  some  time,  the  equilibrium  is  re- 
stored.    See  Interval. 

1.  The  Theory  of  Vibrations  has  been 
adopted  for  explaining  the  phenomena 
of  light,  which  are  supposed  to  depend 
on  the  vibrations,  or  undulations,  of  a  fluid 
called  elher,  diffused  through  all  nature, 
and  set  in  motion  by  the  presence  of 
luminous  bodies.     See  Emission. 

2.  Bodies  of  a  linear  form  are  capable 
of  exhibiting  three  kinds  of  vibration, 
the  transverse,  the  longitudinal,  and  the 
rotatory.  1.  If  a  piece  of  whip-cord  be 
strained  tight  and  firmly  held  at  each 
end,  and  be  then  pulled  in  the  middle 

367 


from  its  position  of  rest,  and  suddenly 
let  go,  it  undergoes  a  series  of  transverse 
vibrations.  2.  If  the  cord  be  held  at  one 
end,  and  a  weight  attached  to  the  other 
end  be  raised,  and  then  let  go,  a  series 
of  longitudinal  vibrations  is  produced. 
3.  Lastly,  if  the  cord  be  twisted  by 
means  of  the  weight,  and  the  weight  be 
suddenly  allowed  to  fall,  the  cord  exhi- 
bits a  series  of  rotatory  vibrations. 

3.  Vibrations,  co-existence  of.  This, 
and  the  equivalent  term  superposition  of 
vibrations,  denote  a  principle  in  mecha- 
nics, which  seems  to  be  only  a  particular 
case  of  what  might  be  called  the  co- 
existence or  superposition  of  small 
changes  of  any  kind.  For  instance,  two 
stones  are  dropped  into  water  at  two 
different  places,  and  at  a  certain  time, 
on  a  certain  part  of  the  surface ;  in  this 
case,  the  resulting  waves  cross  one  an- 
other. If  there  be  a  particle  which  is  at 
the  same  time  raised  on  both  waves, 
say  a  tenth  of  an  inch  from  one,  and 
three-tenths  of  an  inch  from  the  other, 
that  particle  will  altogether  be  raised  four 
tenths  of  an  inch,  or  insensibly  near  to 
it.— Pew.  Cycl. 

VIBRIO'NID^E.  A  tribe  of  animal- 
cules, named  from  the  genus  vibrio,  and 
commonly  known  as  microscopic  eels. 
One  species,  the  vibrio  tritici,  is  parasitic 
on  wheat,  and  it  has  been  computed  that 
50,000  of  them  might  be  contained  in 
a  single  grain  of  wheat.  , . 

Vl'CIEiE  {vicia,  the  vetch).  A  tribe 
of  leguminous  plants,  having  a  papilio- 
naceous corolla,  diadelphous  stamens, 
continuous  legumes,  thick  farinaceous 
cotyledons,  not  changing  in  germination, 
and  a  radicle  curved  inward.  They  in- 
clude the  vetches,  the  bean,  the  pea,  &c. 

VILLOSITY  (villosus,  shaggy).  Shag- 
giness ;  a  term  denoting  that  state  of 
hairiness  in  plants,  in  which  the  hairs 
are  very  long,  very  soft,  erect,  and 
straight,  as  in  epilobium  hirsutura. 
When  in  excess,  the  hairs  are  termed 
crini. 

VIMEN.  A  long  and  flexible  shoot  of 
plants.  This  word  is,  however,  seldom 
used,  the  adjective  being  employed  in- 
stead: thus,  we  say,  rami  viminei,  or 
caulis  vimineus,  and  so  on.     See  Virgate. 

VI'NCULUM.  Literally,  a  bond ;  and, 
hence,  the  term  denotes,  in  algebra,  a 
line  sometimes  used  instead  of  brackets, 
and  drawn  above  quantities  which  are 
connected;  thus  a — b  —  c  is  the  same  as 
a  —  {b  —  c);  and  a  —  b  +  c  x  d  —  e 
means  the  same  as  (a  —  b  +  c)  x  (d — e). 
R4 


VIR 

The  line  which  separates  the  numerator 
from  the  denominator  of  a  fraction  may 
he  regarded  as  a  sort  of  vinculum, 
corresponding,  in  fact,  in  Division  to 
the   bracket   in    Multiplication.    Thus, 

.~  c  implies  that  the  whole  quan- 
tity a  +  b  —  c  is  to  he  divided  by  5. 

VINDEMIA'TRIX.  Pravindemia- 
trix.  A  star  of  the  third  magnitude  in 
the  constellation  Virgo ;  it  took  its  name 
from  the  vintage. 

VINE.  Vilicula.  A  stem  which  trails 
along  the  ground  without  rooting,  or 
entangles  itself  with  other  plants,  to 
which  it  adheres  by  means  of  its  ten- 
drils, as  in  the  vine  and  the  cucumber, 
The  term  is  now  seldom  used.  De 
Candolle  refers  this  kind  of  stem  to  the 
sarmentum  or  runner,  from  which,  how- 
ever, it  essentially  differs  in  its  not  root- 
ing. 

VINEGAR.  Acetic  acid.  A  hydrated 
acid  derived  by  the  action  of  air  upon 
alcoholic  liquors,  as  wine  and  beer ;  but 
the  remarkable  discovery  of  Dr.  J.  Davy, 
that  platinum  black  in  contact  with  alco- 
hol became  incandescent,  and  gave  rise 
to  acetic  acid,  first  led  Dobereiner  to  the 
discovery  that  alcohol,  by  absorbing  oxy- 
gen, gives  rise  to  water  and  acetic  acid, 
without  disengaging  carbonic  acid. 

Wood  vinegar,  or  pyroligneous  acid,  is 
prepared  on  a  large  scale  by  the  distilla- 
ti#  of  wood,  generally  that  of  oak  cop- 
pice deprived  of  the  bark,  which  is  used 
in  tanning. 

VIOLA'CEjE  (viola,  a  violet).  The 
Violet  tribe  of  Dicotyledonous  plants. 
Herbs  with  leaves  usually  alternate; 
flowers  polypetalous ;  petals  hypogynous ; 
stamens  alternate  with  the  petals ;  ova- 
rium 1 -celled,  many-seeded. 

VI'PERID^E.  The  Venom-snakes,  in- 
cluding the  varieties  of  the  vipera  or 
adder,  the  naia,  the  rattle-snake,  the 
horn-snake,  &c. 

VIRGATE  (virga,  a  twig).  A  virgate 
stem  differs  from  a  vimineous  stem  only 
in  being  less  flexible.     See  Vimen. 

VIRGO.  The  Virgin;  the  sixth  of 
the  zodiacal  constellations,  consisting  of 
110  stars,  the  principal  of  which  is  Spica 
Virginis.  It  denotes  the  third  month  of 
winter,  extending  from  the  20th  of 
February  to  the  20th  of  March.  In  the 
Egyptian  zodiacs,  famenoth,  or  the  fruit- 
•  ful  woman,  holds  an  ear  of  corn  in  her 
hand.  The  Greeks  were  led  into  the 
error  of  calling  this  sign  napOevov,  in 
consequence  of  the  Egyptian  word  sig- 
368 


VIS 

nifying  'endowed  with  beauty;'  but  it 
also  involves  the  idea  of  fruitfulness. 

VIRGULTUM.  The  name  sometimes 
given  to  a  young  slender  branch  of  a 
tree  or  shrub. 

VIRTUAL  FOCUS.  A  term  in  Optics 
denoting  the  point  from  which  rays  of 
light,  having  been  rendered  divergent  by 
reflection  or  refraction,  appear  to  issue. 

VIRTUAL  VELOCITY.  The  velo- 
city which  a  body  in  a  state  of  equi- 
librium would  actually  acquire  during 
the  first  instant  of  its  motion,  in  case  of 
the  equilibrium  being  disturbed.  If  we 
suppose  a  point  at  which  any  force  acts 
to  be  slightly  displaced,  and  from  the 
new  position  of  the  point  a  perpendicular 
to  be  dropped  upon  the  direction  of  the 
force,  then  the  line  intercepted  between 
the  foot  of  this  perpendicular  and  the 
original  position  of  the  point  is  called  the 
Virtual  Velocity  of  the  force. 

1 .  Thus,  let  O  be  the  point  at  which 
the  force  P  acts,  and  suppose  it  to  be 
slightly  displaced,  so  as  to  be  brought 
into  the  position  O';  from  O' draw  the 
perpendicular  O'N  on  OP,  then  ON  is 
the  Virtual  Velocity  of  P. 


ZL 

O        N 


-5* 


2.  The  Principle  of  Virtual  Velocities 
is  thus  stated :  When  a  system  of  bodies 
is  in  equilibrium  under  the  action  of  any 
forces,  then  if  the  system  be  very  slightly 
displaced,  the  sum  of  each  force  multi- 
plied by  its  virtual  velocity  will  equal 
zero. 

VIS.  Force ;  a  term  employed  by  the 
older  writers  on  mechanics  to  denote 
power  or  force  of  any  kind.  Thus  we 
have  vis  mortua  and  vis  viva ;  the  former 
relating  to  the  pressure,  the  latter  to  the 
force  of  a  body  in  motion,  estimated  by 
the  distance  to  which  the  body  goes ;  via 
motrix,  vis  acceleratrix,  vis  inertice,  &c. 

VIS  INERTIA.  Inertness,  or  the 
principle  of  inactivity,  by  which  a  body 
perseveres  in  the  same  state  of  rest  or 
motion,  in  a  straight  line,  unless  obliged 
to  change  it  by  a  foreign  force. 

VISCOUS  FERMENTATION.  At  a 
temperature  between  86°  and  104°,  the 
saccharine  juices  of  plants  containing 
albumen  or  other  azotised  matter,  un- 
dergo a  species  of  fermentation,  which  is 
different  from  the  vinous,  combustible 
gases  being  evolved  with  carbonic  acid, 
and  a  gummy  matter  formed,  having  the 


VIS 


VI  V 


composition  of  gum  Arabic,  which  ren- 
ders the  liquid  ropy  and  thick,  and  hence 
the  application  of  the  name  viscous  to 
this  fermentation.     See  Fermentation. 

VISION.  In  Optics,  the  sense  of 
sight ;  this  sense  is  produced  by  certain 
nerves  which  convey  to  the  brain  intel- 
ligence of  figures  impressed  by  rays  of 
light  upon  the  retina  of  the  eye.  Short- 
sightedness is  occasioned  by  the  con- 
vergence of  the  rays  to  a  point  before 
they  fall  upon  the  retina,  and  a  concave 
lens  is  employed  to  delay  their  conver- 
gence. Long-sightedness  is  occasioned  by 
the  non-conveyance  of  the  rays  to  a  point 
until  they  have  passed  the  retina,  and  a 
convex  lens  is  employed  to  promote  their 
convergence. 

1.  Vision  recrossed.  A  term  applied 
by  Captain  J.  Grover  to  a  distinct  tribe 
of  ocular  phenomena,  in  which  objects 
placed  between  and  very  near  the  eyes, 
such  as  the  two  sides  of  the  nose,  appear 
on  opposite  sides  of  the  sphere  of  vision : 
the  object  on  the  right  side  of  the  nose 
being  seen  to  the  left  by  the  right  eye, 
and  that  which  is  on  the  left  of  the  nose 
being  seen  to  the  right  by  the  left  eye. 
It  is  supposed  that,  besides  the  two  ex- 
ternal or  cranial  eyes,  "  man  is  endowed 
with  an  internal  cerebral  organ,  which 
performs  the  office  of  a  third  eye,  by 
being  the  common  recipient  of  impres- 
sions propagated  either  from  one  or  both 
of  the  external  eyes ;  and  the  mind,  in 
her  chamber  of  percipience.  steers  with 
regard  to  external  objects  by  the  same 
principle  on  which  the  mariner  steers  by 
his  compass. 

2.  "Thus  the  two  cranial  eyes  are 
analogous,  in  principle  and  situation,  to 
two  magnetic  compasses  placed  upon  a 
ship's  deck ;  while  the  third,  or  cerebral 
eye,  corresponds  to  another  compass 
in  the  cabin  below ;  and  the  mind,  situ- 
ated like  the  captain-mariner  in  his 
cabin,  knows,  from  consulting  the  cere- 
bral eye,  on  what  point  of  direction  the 
body  is  steering ;  although  the  mind  no 
more  perceives  either  any  external  object, 
nor  yet  any  image  in  the  cranial  eye, 
than  the  mariner  perceives  (even  in  the 
vulgar  sense  of  the  word  perceiving)  the 
far-off  land,  or  haven,  towards  which  he 
is  surely  making  his  way." 

VISUAL  (visus,  sight).  That  which 
accompanies  vision :  the  visual  angle  is 
the  angle  under  which  a  body  is  seen ; 
and  the  apparent  magnitude  of  the  same 
object,  when  viewed  at  different  dis- 
tances, depends  on  the  size  of  the  visual 
869 


angle — that  is,  the  angle  formed  at  the 
eye  by  the  rays  proceeding  from  the  ex- 
tremities of  the  object.     See  Theodolite. 

VITA'CEJE  [vitis,  a  vine).  The  Vine 
tribe  of  Dicotyledonous  plants.  Climbing 
shrubs  with  tumid  joints,  and  leaves  sti- 
pulate ;  flowers  polypetalous,  on  ramose 
peduncles ;  stamens  hypogynous  ;  ova- 
rium 2-celled ;  fruit  baccate ;  seeds  albu- 
minous. 

VITAL  AIR.  A  term  applied  to 
oxygen  gas,  from  its  being  indispensable 
to  the  maintenance  of  life.  It  was  for- 
merly called  dephlogisticated  air,  em- 
pyreal air,  &c. 

VITE'LLUS.  Literally,  the  yoke  of  an 
egg;  a  term  applied  by  Gcertner  to  a 
fleshy  sac  occasionally  interposed  be- 
tween the  albumen  and  the  ovule,  in 
plants,  enveloping  the  latter.  This  sac 
is  usually  referred  to  the  vesicula  amnios 
of  Malpighi. 

VITRIFICATION  {vitrum,  glass,  fio, 
to  become).  The  conversion  of  a  sub- 
stance, as  silica,  into  glass. 

VI'TRIOL  (vitrum,  glass).  A  term 
originally  applied  to  any  crystalline  body 
possessing  a  certain  degree  of  transpa- 
rency, but  now  restricted  to  three  sul- 
phates— that  of  iron,  called  ferrous  oxide, 
copperas,  or  green  vitriol ;  that  of  copper, 
or  blue  vitriol ;  and  that  of  zinc,  or  white 
vitriol. 

1.  When  Green  Vitriol  is  expqsed  to 
heat  in  a  retort,  it  first  gives  off  water  of 
crystallization,  ox  phlegm  of  vitriol ;  next 
comes  an  acid,  called  spirit  of  vitriol; 
then  a  stronger  acid,  called  oil  of  vitriol ; 
the  latter  part  of  this  becomes  solid,  and 
has  been  called  glacial  oil  of  vitriol. 

2.  The  stalactitic  cobalt-vitriol,  from 
Herrengrund  in  Hungary,  is  sulphate  of 
magnesia,  coloured  red  by  oxide  of  co- 
balt. 

VITTjE  (vitta,  a  riband).  A  term  ap- 
plied, in  Botany,  to  little  clavate  vessels 
of  oil  found  in  the  coat  of  the  fruit  of 
umbelliferous  plants  ;  when  situated 
in  the  valleculas,  or  depressions  be- 
tween the  ridges  of  the  fruit,  they  are 
termed  dorsal ;  when  on  the  face  of  the 
fruit,  commissural.  They  offer  a  special 
case  of  the  vasa  propria,  or  receptacles 
of  secretion.  Modifications  of  these 
vessels  are  found  in  the  leaves  of  the 
orange  and  of  all  myrtaceous  plants, 
where  they  are  called  crypts,  vesicular 
glands,  or  receptacles  of  oil.  See  Vessels, 
Milk,  #c. 

VIVE'RRIDjE  (viverra,  the  civet). 
The  civets ;  a  group  of  animals  placed  by 
R5 


VOI 


VOL 


Cuvier  between  the  dogs  and  the  hyenas, 
which  are  immediately  followed  by  the 
cats.  They  comprise  the  civets,  properly 
so  called ;  the  genets ;  the  paradoxure  ; 
the  mangoustes ;  the  suricates ;  and  the 
mangues. 

VI'VIANITE.  Phosphate  of  iron;  a 
mineral  occurring  in  variously  grouped 
crystals  in  Bodenmais  in  Bavaria,  in 
Cornwall,  &c,  massive  and  pulverulent. 

VI VT PAROUS  (vivus,  alive,  pario, 
to  bring  forth).  A  term  applied  to  ani- 
mals which  bring  forth  their  young  alive 
and  perfect,  as  distinguished  from  ovi- 
parous animals,  which  produce  their 
young  in  the  egg. 

VOICE,  SCALE  OF.  The  scale  of  the 
human  voice  comprises  four  octaves,  viz. 
from  mi  or  E  in  the  bass,  to  mi  or  E4  in 
the  treble  clef.  Of  this  scale,  the  male 
voice  extends  from  E  in  the  bass  to  C3  in 
the  treble  ;  the  female,  from  F1  to  E4  in 
the  treble 

1.  Subordinate  scales.  There  are  four 
scales  of  vocal  music.  The  scale  of  the 
male  voice  is  distinguished  into  bass  and 
tenor,  each  containing  two  octaves,  the 
bass  extending  from  E  to  F2,  the  tenor 
from  C1  to  C3.  Eleven  notes  are  common 
to  the  bass  and  the  tenor  scales.  The 
scale  of  the  female  voice  is  distinguished 
into  contralto  and  soprano,  each  contain- 
ing two  octaves,  the  contralto  ranging 
from  Fi  to  F3,  the  soprano  from  C2  toE4. 
Twelve  notes  are  common  to  the  tenor 
and  the  contralto,  eight  to  the  tenor  and 
the  soprano  scales.  The  terms  alto,  con- 
tralto, and  counter-tenor  are  synony- 
mous. 

2.  The  barytone  is  a  scale  of  the 
male  voice  intermediate  between  the 
bass  and  the  tenor,  and  ranging  from 
A  to  F2.  The  mezzo-soprano  is  a  scale 
of  the  female  voice  intermediate  between 
the  contralto  and  the  soprano,  and  rang- 
ing from  A1  to  A3. 

3.  Registers.  The  compass  of  the 
soprano  and  of  some  other  voices  is  dis- 
tinguished into  two  registers,  the  natural 
and  the  falsetto.  The  former  is  termed  by 
the  Italians  voce  di  petto,  or  chest-voice  ; 
the  latter  voce  di  testa,  or  head-voice. 
The  Italians  combine  these  two  registers 
by  a  third,  called  mezzo  f also,  or  middle 
falsetto.  The  uppermost  notes  of  the 
falsetto  are  sometimes  called  flautino,  or 
flute  register.  "When  the  pitch  of  a  voice 
proceeds  lower  than  the  natural  register, 
such  a  voice  is  called  basso  falsetto,  or 
lower  falsetto. 

4.  Song-note;    Speech-note,      1.    The 

370 


song-note  is  a  musical  sound  of  some 
fixed  pitch  in  the  musical  scale.  The  scales 
comprising  the  song  sounds  are  described 
under  the  articles  chromatic,  diatonic, 
and  enharmonic  scales.  2.  The  speech- 
note  is  of  two  kinds,  the  simple  and  the 
compound ;  the  former  consists  of  a 
single  rising  or  falling  of  the  voice,  rang- 
ing from  a  semitone  to  an  octave ;  the 
latter  consists  of  a  falling  and  a  rising,  or 
of  a  rising  and  a  falling,  combined  in 
various  circumflexes. 

VOLATILITY  (volatilis,  from  volo, 
to  fly).  A  property  of  bodies,  by  which 
they  are  disposed  to  assume  the  state  of 
vapour  and  fly  off,  on  the  application  of 
heat. 

VOLCANIC  BOMBS.  Masses  of 
melted  lava  sometimes  thrown  out  by 
volcanoes;  these,  as  they  fall,  assume 
rounded  forms,  like  bomb-shells,  and  are 
often  elongated  into  the  shape  of  a  pear. 

VOLCANIC  FOCI.  The  subterranean 
centres  of  action  in  volcanoes,  where  the 
heat  is  supposed  to  be  in  the  highest 
degree  of  energy. 

VOLCANIC  ROCKS.  The  geological 
designation  of  the  fourth  or  most  recent 
class  of  rocks,  which  are  evidently  com- 
posed of  lavas,  or  masses  of  melted  rocky 
matter,  which  have  been  sent  upward  by 
volcanoes.  This  kind  of  rock  is  also 
called  igneous  rock. 

VO'LCANITE.  Another  name  for 
augite,  from  its  being  found  among  vol- 
canic rocks ;  but  it  is  supposed  to  have 
existed  prior  to  the  eruption  and  ejec- 
tion of  the  lava.     See  Augite. 

VOLCANO  (Vulcanus,  the  fabled  god 
of  fire).  An  opening  in  the  earth's  sur- 
face, presenting  the  general  appearance 
of  a  vent  of  subterranean  fire,  from  which 
smoke,  cinders,  ashes,  and  sometimes 
large  fragments  of  rock,  and  vast  quan- 
tities of  melted  rocky  matter,  are  con- 
tinually discharged. 

Mud  volcanoes  are  so  termed  from 
their  having  eruptions  of  mud  only.  The 
mountain  of  Maccaluba  in  Sicily,  and 
some  hills  at  the  town  of  Taman  in  the 
Cri nea,  are  distinguished  by  eruptions 
of  this  kind. 

Extinct  volcanoes  are  those  mountains 
which  bear  evident  marks  of  having  at 
some  very  distant  period  been  outlets  of 
fire. 

VOLITATRFCES  (volito,  to  flutter). 
Gliders  ;  a  term  applied  by  Mac  Gillivray 
to  an  order  of  birds,  which  have  a  pecu- 
liarly light  and  bounding  flight,  are 
incapable   of   walking   efficiently  or  of 


VOL 


VUL 


advancing  to  any  distance  on  the  ground 
or  on  trees.  They  are  divided  into  the 
Cypselinae  or  Swifts,  the  Hirundinae  or 
Swallows,  and  the  Caprimulginae  or  Goat- 
suckers. 

VO'LKONSKOITE.  A  mineral  con- 
taining oxide  of  chromium,  and  found  in 
thin  veins  and  nests  in  Mount  Jess- 
mictski,  in  Siberia. 

VOLTA-ELECTROMETER.  A  new 
instrument  for  the  exact  measurement 
of  electric  currents.  The  current  to 
be  measured  is  made  to  pass  through 
water  acidulated  by  sulphuric  acid,  and 
the  gases  evolved  by  its  decomposition 
are  collected  and  measured,  thereby 
giving  at  once  an  expression  of  the  quan- 
tity of  electricity  which  has  passed.  The 
principle  on  which  this  conclusion  is 
founded  is  this  new  law,  "  that  the  decom- 
posing action  of  any  current  of  Elec- 
tricity is  constant  for  a  constant  quantity 
of  electricity." 

VOLTA-METER.  An  instrument  for 
measuring  the  intensity  of  the  electric 
current.  It  consists  of  a  cell  of  decom- 
position, containing  dilute  sulphuric 
acid,  and  so  formed  as  to  admit  of  the 
collection  and  measurement  of  the 
evolved  gases.  The  electrolyte  which 
best  fulfils  all  the  requirements,  is  water ; 
and  any  arrangement  in  which  a  stream 
of  electricity  is  made  to  decompose  it,  if 
furnished  with  the  means  for  measuring 
the  quantity  of  gas  thus  generated,  may 
be  regarded  as  a  volta-meter. 

VOLTAIC  CIRCLES.  If  a  plate  of 
zinc  and  a  plate  of  copper  be  immersed 
to  a  certain  depth  in  a  vessel  containing 
dilute  sulphuric  acid,  and  connected 
together  by  direct  contact,  a  current  of 
positive  electricity  passes  uninterruptedly 
from  the  zinc  through  the  liquid  to  the 
copper,  and  from  the  copper  to  the  zinc, 
in  the  direction  of  the  arrows.  Such 
an  arrangement  is  termed  a  simple 
voltaic  circle.  When  it  is  required  to 
produce  more  decided  effects,  a  series 
of  these  plates  is  combined,  form- 
ing what  is  called  a  compound  voltaic 
circle. 

VOLTAIC  ELECTRICITY.  The  phe- 
nomena of  electricity,  observed  hy  Gal- 
vani,  and  hence  termed  Galvanism  and 
animal  electricity,  were  attributed  by 
Volta  to  the  disturbance  of  the  electric 
equilibrium  by  the  contact  of  two  dissi- 
milar metals.  The  identity  of  the  com- 
.  mon  and  the  galvanic  electricities  was 
proved  by  the  discovery  of  the  voltaic 
pile,  and  the  science  has  from  that  period 
371 


been  termed  by  some  writers,  Voltaism 
or  Voltaic  Electricity. 

VO'LTATYPE.  A  term  synonymous 
with  electrotype,  applied  to  a  new  art  of 
plating  performed  by  electro-chemical 
action. 

VOLTZITE.  Oxysulphuret  of  zinc, 
occurring  in  the  form  of  small  hemi- 
spheres, divisible  into  thin  layers.  It 
occurs  at  Roziers  in  France,  and,  as  is 
said,  in  Cornwall. 

VOLUBLE  (volubilis,  from  volvo,  to 
twist).  Twisting;  as  applied  to  stems 
which  twist  or  twine  round  other  bodies, 
that  of  the  hop  to  the  right,  that  of  the 
bindweed  to  the  left. 

VOLUME  (volumen,  from  volvo,  to 
roll).  The  apparent  space  which  a  body 
occupies  is  called  its  volume;  the  effec- 
tive space  which  the  same  body  occupies 
or  its  real  bulk  of  matter,  is  its  mass; 
the  relation  of  the  mass  to  the  volume 
(or  the  quotient  of  the  one  by  the  other) 
is  its  density ;  and  the  empty  spaces,  or 
voids,  which  render  the  volume  larger 
than  the  mass,  are  its  pores. 

Definite  Volumes.  The  union  of  gases 
is  always  effected  in  simple  proportions 
of  their  volumes :  a  volume  of  one  gas 
combines  with  an  equal  volume,  or  twice 
or  three  times  the  volume,  of  another 
gas,  and  in  no  intermediate  proportion  ; 
this  is  called  the  law  of  definite  volumes. 

VOLU'Tiaffi.  The  Volutes;  a  fa- 
mily of  testaceous,  carnivorous  gastero- 
pods,  named  from  the  typical  genus  vo- 
luta;  the  column  of  the  shell  is  regu- 
larly plaited,  and  the  mantle  much  de- 
veloped in  the  typical  species. 

VOLUTION  (volutus,  rolled).  A  term 
synonymous  in  Malacology  with  whorl. 

VOLVA  {volo,  to  roll).  The  wrapper, 
or  involucrum-like  base  of  the  stipes 
of  agaric.  It  originally  was  a  bag  en- 
veloping the  whole  plant,  and  was  left  at 
the  foot  of  the  stipes,  when  the  plant 
elongated  and  burst  through  it. 

VORTICES,  HYPOTHESIS  OF  {vor- 
tex, a  whirlpool).  The  primary  hypo- 
thesis of  the  natural  philosophy  of  Des- 
cartes was,  that  the  universe  is  a, plenum, 
that  is,  without  any  vacuum  or  unoccu- 
pied space  ;  and  that  the  atoms  of  matter 
moved  in  numerous  vortices,  which  car- 
ried the  heavenly  bodies  around  their 
several  centres  of  motion ;  such  as  the 
planets  about  the  sun,  and,  perhaps, 
similar  planets  around  the  fixed  stars. 

VULPECULA  ET  ANSER.  The  Fox 
and  the  Goose ;  a  modern  northern  con- 
i  stellation,    consisting    of    thirty-seven 


WAR 


WAT 


stars,  and  situated  immediately  above 
Aquila  and  Sagitta. 

VU'LPIKIN.  Vulpinic  acid.  An  acid 
substance  obtained  from  the  evernia  vul- 
pina  of  Achard,  or  the  lichen  vulpinus  of 
Linnaeus. 

VU'LPINITE.  A  mineral  substance 
consisting  of  sulphate  of  lime  and  silica, 
and  occurring  together  with  granular 
foliated  limestone  at  Vulpino  in  Italy, 


where  it  is  employed  for  ornamental 
works  under  the  name  of  marmo  bar- 
diglio. 

VULTU'RIDjE.  The  Vulture  tribe ; 
a  family  of  the  Raptores,  or  rapacious 
birds,  characterized  by  their  untoothed 
beak,  and  by  the  moderate  curvature  of 
their  talons,  as  compared  with  the  fal- 
cons, and  by  their  head  and  part  of  their 
neck  being  destitute  of  feathers. 


w 


WACKE'.  A  simple  trap  rock  nearly 
allied  to  basalt,  of  which  it  may  be  con- 
sidered as  a  soft  and  earthy  variety. 
Ure  states  that  it  never  contains  augite 
or  olivine ;  sometimes  it  is  vesicular, 
presenting  amygdaloidal  cavities  filled 
with  various  substances. 

WA  DD.  A  technical  name  for  plum- 
bago or  black  lead.  Black  wadd  is  an 
ore  of  manganese  found  in  Derbyshire, 
remarkable  for  its  property  of  taking  fire 
when  mixed  with  lintseed  oil. 

WA'GNERITE.  A  rare  mineral, 
formerly  confounded  with  the  Brazilian 
topaz.  It  consists  of  the  phosphoric  and 
the  fluoric  acids,  magnesia,  iron,  and 
manganese.  It  occurs  at  Salzburg  in 
small  veins  of  quartz  in  clay-slate. 

WAKE  OF  A  SHIP.  A  nautical 
term  denoting  the  smooth  water  which  is 
astern  of  a  ship  under  sail.  It  serves  to 
show  the  way  the  ship  makes:  if  the 
wake  be  right  astern,  she  makes  her  way 
forward;  if  it  be  to  leeward  a  point  or 
two,  she  falls  to  the  leeward  of  her 
course.  A  ship  is  said  to  stay  to  the 
weather  of  her  wake,  when,  in  her  stay- 
ing, she  is  so  quick,  that  she  does  not 
fall  to  leeward  upon  a  tack,  but  that 
when  she  is  tacked,  her  wake  is  to  the 
leeward ;  and  it  is  a  sign  that  she  feels 
her  helm  very  well,  and  is  quick  of  steer- 
age. 

WANING.  Declining  in  power.  The 
term  is  applied  to  the  moon,  as  decrea- 
sing in  her  light,  as  she  proceeds  from  the 
full  to  the  change. 

WARM-BLOODED  ANIMALS.  A 
term  applied  to  two  classes  of  vertebrate 
animals,  viz.  the  mammals  and  the  birds. 
In  these  there  are  two  hearts,  perfectly 
distinct  from  each  other ;  and  a  twofold 
circulation,  viz.  that  which  takes  place 
in  the  lungs,  called  the  pulmonic,  and 
that  which  takes  place  through  the 
372 


entire  system,  called  the  systemic  circu- 
lation. 

WARP.  The  deposit  of  muddy  waters, 
artificially  introduced  into  low  lands.  In 
the  operation  of  warping,  it  is  only  ne- 
cessary to  produce  a  stagnation  of  the 
water  for  a  few  hours  to  have  a  copious 
deposit,  leaving  the  water  clear  over  it. 

WASH.  A  technical  term  for  the 
fermented  liquor,  of  any  kind,  from 
which  spirit  is  intended  to  be  distilled. 

WATER.  Protoxide  of  hydrogen;  a 
liquid  produced  by  the  combustion  of 
oxygen  and  hydrogen,  consisting  of  two 
volumes  of  the  latter  to  one  volume  of 
the  former  gas,  and  of  eight  parts  of  the 
former  to  one  of  the  latter  by  weight. 

Water,  oxygenated.  Peroxide  of  hy- 
drogen ;  a  liquid  containing  twice  as 
much  oxygen  as  water,  but  less  volatile, 
having  a  metallic  taste,  and  instantly 
bleaching  litmus  and  other  organic  co- 
louring matters. 

WATER  OF  CRYSTALLIZATION. 
That  portion  of  water  which  combines  in 
a  dry  state  with  many  substances,  form- 
ing an  essential  condition  of  their  crys- 
talline character.  Salts  which  retain  this 
water  so  feebly,  that  it  passes  off  on  ex- 
posure to  the  air,  leaving  the  salt  in  a 
pulverulent  state,  are  termed  efflorescent; 
while  those  which  have  so  great  an  affi- 
nity for  it,  that  their  crystals  attract  more 
of  it  from  the  air,  and  become  dissolved 
in  it,  are  called  deliquescent. 

WATER-CLOCK.  Clepsydra.  A  cy- 
lindrical vessel  with  its  surface  divided 
by  lines  into  portions  which  are  to  one 
another  as  the  odd  numbers,  1,  3,  5,  7, 
&c,  taken  backward.  Supposing  such 
a  vessel  required  six  hours  to  empty 
itself,  let  it  be  divided  into  36  equal 
parts ;  then,  beginning  from  the  surface,  , 
take  eleven  of  those  parts  for  the  first 
hour,  nine  for  the  second,  seven  for  the 


WAT 


WEB 


third,  five  for  the  fourth,  three  for  the 
fifth,  and  one  for  the  sixth;  it  Mill  he 
found  that  the  surface  of  the  water  will 
descend  regularly  through  each  of  those 
divisions  in  an  hour. 

WATER-GILDING.  The  process  of 
gilding  by  the  application  of  an  amalgam 
of  gold  to  the  surface  of  metals;  the 
mercury  of  the  amalgam  is  driven  off  by 
heat,  and  a  thin  coating  of  gold  remains. 

WATER-SPOUT.  A  meteorological 
phenomenon  of  the  same  class  probably 
as  the  whirlwinds  which  raise  pillars  of 
sand  in  the  deserts  of  Africa.  A  column 
of  water  is  observed  to  descend  from  a 
cloud,  until  it  meets  a  column  rising 
from  the  sea ;  the  two  unite,  and  often 
move  with  great  rapidity,  until  they 
meet  with  some  opposing  wind,  or  other 
cause,  which  destroys  them. 

Water-tight.     That  degree  of 

closeness  of  a  vessel  or  tube,  which  pre- 
vents the  ingress  or  the  egress  of  water. 

WATER-WHEEL.  A  machine  in- 
vented by  Segner  for  employing  the  pres- 
sure of  water  in  the  production  of  a  rota- 
tory motion.  It  consists  of  a  hollow  cylin- 
der, turning  upon  a  vertical  axis,  and 
kept  full  of  water.  At  its  base  are  seve- 
ral pipes  for  the  issue  of  the  water ;  the 
apertures  of  the  pipes  are  all  in  one  di- 
rection, tangential  to  the  circumference 
of  the  cylinder.  The  pressure  produced 
against  the  sides  of  the  pipes  produces 
a  motion  of  the  cylinder  in  an  opposite 
direction.  The  motion  ceases  if  the 
water  flow  in  an  opposite  direction  from 
an  equal  number  of  pipes. 

WATERS,  MINERAL.  A  term  con- 
ventionally applied  to  waters  distin- 
guished from  all  others  by  their  peculiar 
ingredients  or  supposed  medicinal  effects. 

1.  Chalybeate  waters  contain  iron,  most 
commonly  in  the  state  of  carbonate  dis- 
solved in  carbonic  acid,  the  proportion 
rarely  exceeding  one  grain  in  a  pound  of 
water.  They  occur  at  Brighton,  Chelten- 
ham, Bath,  &c. 

2.  Sulphureous  waters  contain  sul- 
phuretted hydrogen  gas,  in  a  proportion 
not  exceeding  that  of  air  in  spring  water, 
and  no  oxygen.  They  are  recognized  by 
their  peculiar  odour,  and  by  their  blacken- 
ing silver  and  salts  of  lead.  They  occur 
at  Harrowgate,  Aix-la-Chapelle,  &c. 

3.  Saline  waters  contain  various  salts 
of  lime  and  magnesia,  and  generally 
common  salt;  their  density  is  always 
considerably  higher  than  that  of  pure 
water.  They  occur  at  Leamington,  Chel- 
tenham,   Seidlitz,    &c.    Sea-water   con- 

373  ' 


tains  3£  per  cent,  of  saline  matter,  and 
has  a  density  of  1.0274. 

WAVE.  The  simplest  idea  of  a  wave 
may  be  obtained  by  observing  the  curve 
produced  by  a  cord  when  its  equilibrium 
has  been  disturbed.  The  portion  of  the 
curve  which  rises  above  the  original  posi- 
tion of  the  cord,  is  the  elevation  of  the 
wave  ;  that  which  falls  below  the  original 
position  of  the  cord,  is  the  depression  of 
the  wave.  These  movements  occur  in 
solid,  in  liquid,  and  in  aeriform  bodies. 
See  Undulation. 

WA'VELLITE.  Phosphate  of  alu- 
mina; a  mineral  sibstance  which  was 
originally  mistaken  for  a  hydrate  of  pure 
alumina,  and  hence  called  hydrargyllite. 
It  occurs  in  Devonshire,  where  it  was 
first  found  by  Dr.  Wavell ;  at  Amberg  in 
Bavaria,  where  it  is  called  lasionite;  in 
Greeenland,  &c. 

WAVY.  Undulated.  This  term  is 
applied,  in  botanical  language,  to  a  leaf, 
which  has  an  uneven,  alternately  convex 
and  concave  margin,  as  in  holly.  In 
entomology,  it  is  applied  to  an  insect 
which  has  the  margin  of  its  body  marked 
by  a  series  of  arched  incisions. 

WEALD  CLAY.  The  upper  portion 
of  the  Wealden  Formation,  consisting  of 
beds  of  clay,  sandstone,  calcareous  sand- 
stone, conglomerate,  limestone,  and  iron- 
stone. The  term  weald  has  been  given 
to  a  valley,  or  tract  of  country,  lying 
between  the  North  and  the  South  Downs 
of  Kent  and  Sussex. 

WEALDEN  ROCKS  {wald,  German, 
a  wood).  A  series  of  rocks  which  imme- 
diately cover  the  upper  oolites  without 
any  breach  of  continuity.  They  are 
essentially  of  fresh-water  origin,  and  in 
this  respect  they  bear  the  same  relation 
to  our  older  secondary  rocks  which  the 
old  carboniferous  system  bears  to  the 
inferior  palaeozoic  groups.  The  lowest 
part  of  this  formation  is  the  Purbeck 
Limestone;  above  this  is  the  Hastings 
Sand ;  the  uppermost  portion  is  the 
Weald  Clay. 

WEATHER-GLASS.  The  popular 
name  for  the  barometer,  the  variations 
of  this  instrument  being  commonly  sup- 
posed to  indicate  approaching  changes  in 
the  state  of  the  weather.  In  former 
times,  the  same  appellation  was  given  to 
the  thermometer. 

WE'BSTERITE.  Aluminite.  Hy- 
drous subsulphate  of  alumina,  found  in 
Sussex  and  at  Halle  in  Magdeburg,  and 
formerly  mistaken  for  pure  alumina,  also 
for  hydrate  of  alumina  with  mechanically 


WEI 


WEI 


admixed  sulphate  of  lime.  This  mineral 
must  not  be  confounded  with  another 
substance  also  called  aluminite  or  alum- 
stone  (alunite  of  some  mineralogists)  from 
Tolfa,  &c,  which  is  a  basic  sulphate  of 
alumina  and  potassa. 

WEDGE.  One  of  the  mechanical 
powers,  consisting  of  a  triangular  prism, 
or  a  pair  of  inclined  planes  having  a  com- 
mon base,  made  of  some  hard  substance, 
and  employed  to  remove  two  objects  from 
one  another  laterally,  or  to  cleave  asunder 
the  parts  of  a  body.  When  the  edge  is 
introduced,  the  wedge  is  driven  forward 
by  a  violent  blow,  as  from  a  hammer, 
which  generates  an  enormous  force,  of 
momentary  duration.  Nails,  awls,  needles, 
and  many  cutting  instruments  act  on  this 
principle ;  the  stones  of  an  arch  are  trun- 
cated wedges. 

WEEK,  DAYS  OF.  The  English 
names  of  the  days  of  the  week  are  de- 
rived from  the  Saxons ;  and  these  partly 
adopted  the  names  from  the  more  civil- 
ized nations  of  antiquity.  Tuesday, 
Wednesday,  Thursday,  and  Friday  are 
derived  respectively,  from  the  names  of 
Tiw,  Woden,  Thor,  and  Friga,  deities  of 
the  ancient  Saxons ;  Thor  being  the  god 
of  thunder,  as  well  as  the  ancient  Jove  ; 
and  Friga,  the  wife  of  Woden.  Saturday, 
Sunday,  and  Monday,  are  derived  re- 
spectively, from  the  Saxon  Seterne's, 
Sun's,  and  Moon's  day. 

WEIGHT.  The  comparative  measure 
of  the  gravity  of  bodies  at  the  earth's 
surface.  In  mechanics,  weight  is  the 
resistance,  or  the  thing  to  be  moved  by 
the  force  of  the  power :  the  stone  is  the 
weight  to  be  moved  by  the  force  of  the 
lever  or  bar. 

WEIGHT  OF  THE  ATMOSPHERE. 
The  mean  weight  of  the  atmosphere  at 
the  surface  of  the  sea  is  generally  esti- 
mated as  equal  to  the  weight  of  a  column 
of  mercury  of  30  inches  in  height,  which 
is  about  15  pounds  on  the  square  inch 
of  surface,  and  is  equivalent  to  a  column 
of  water  of  nearly  34  feet  in  height. 
Hence  the  surface  of  the  globe  sustains  a 
weight  of  11,449,000,000  hundreds  of 
millions  of  pounds. 

WEIGHTS  AND  MEASURES.  The 
following  standards  have  been  sanctioned 
by  Parliament  for  the  purpose  of  ascer- 
taining and  establishing  uniformity  of 
weights  and  measures  : — 

ENGLISH    MEASURES    AND   WEIGHTS. 

1.  Lineal,  Superfitial,  and  Solid  mea- 
sures.    The  length  of  the  pendulum, 
374 


vibrating  seconds  of  mean  time  in  the 
latitude  of  Loudon  at  62°  Fahr.,  and  in 
a  vacuum  at  the  level  of  the  sea,  is  equal 
to  39.1393  inches  of  the  Brass  "  Standard 
Yard  of  1760,"  or  "Imperial  Standard 
Yard."  Hence  the  length  of  the  yard  to 
that  of  the  pendulum  is  in  the  proportion 
of  36  inches  to  39.1393  inches,  or  of  the 
number  360,000  to  the  number  391.393  : 
so  that,  if  the  length  of  the  pendulum 
be  divided  into  391.393  equal  parts,  then 
will  10,000  of  these  parts  be  the  length 
of  an  inch,  according  to  the  imperial 
standard. 

2.  The  English  land-chain  =  22  yards 
or  66  feet,  and  contains  100  links ;  1  link 
m  7.92  inches.  The  square  chain  =  484 
square  yards,  and  10  square  chains  = 
1  acre. 

3.  Troy  and  Avoirdupois  weights.  The 
old  Troy  pound  is  the  standard  unit  of 
weight,  and  contains  5760  grains ;  while 
the  avoirdupois  pound,  now  in  use,  con- 
tains 7000  grains.  Hence,  the  standard 
pound  is  to  the  common  pound  as  5760 
grains  to  7000  grains ;  or  as  the  number 
144  to  the  number  175.  According  to  the 
standard,  one  cubic  inch  of  distilled 
water  at  62°  Fahr.,  the  barometer  being 
at  30  inches,  weighs  252.458  troy  grains, 
one  pound  =  5760  grains.  (A  cubic  inch 
of  distilled  water,  at  the  maximum  den- 
sity, weighs  253  troy  grains).  Then  175 
troy  pounds  =  144  avoirdupois  pounds; 
and  175  troy  ounces  =  192  avoidupois 
ounces.  A  cubic  foot  of  distilled  water 
at  62°  Fahr.  weights  almost  exactly 
997.136969  ounces  avoirdupois,  and  at 
the  maximum  density,  999.2777  ounces 
avoirdupois. 

4.  Imperial  Gallon  Measure.  This  is 
the  measure  for  all  sorts  of  liquids,  corn, 
and  other  dry  goods.  Ten  pounds  avoir- 
dupois, or  277.274  cubic  inches  of  dis- 
tilled water  at  62°  Fahr.,  the  barometer 
being  at  30  inches,  are  the  contents  of 
the  New  Imperial  Gallon.  As  252.458 
grains  \  1  cubic  inch  ;  |  lOlbs.  or  70,000 
grains  I  277.274  cubic  inches,  which  is, 
consequently,  the  content  of  the  impe- 
rial gallon.  The  proportion  of  the  impe- 
rial gallon  to  the  wine  gallon  is  as  6  to  5 
nearly,  to  the  ale  gallon  as  59  to  60  nearly, 
and  to  the  corn  gallon  as  33  to  32  nearly ; 
its  proportion  to  the  sterling  pint  is  as 
59  to  22  nearly. 

5.  Heaped  Measure.  Eighty  pounds 
avoirdupois,  or  2218.192  cubic  inches  of 
distilled  water  at  62°  Fahr.,  the  barometer 
being  at  30  inches,  are  the  contents  of 
the  New  Bushel,  which  is  to  be  made 


WEI 


WEI 


"round,  with  a  plain  and  even  bottom, 
being  19^  inches  from  outside  to  outside," 
and  to  be  heaped  in  the  form  of  a  cone  to 
the  height  of  6  inches.  This  is  the  mea- 
sure for  coal,  culm,  lime,  fish,  potatoes, 
fruit,  &c. 

6.  The  depth  of  the  Imperial  Bushel  is 
required  by  the  Act  to  be  8  inches, 
though  this  is  not  expressed ;  because 
the  height  of  the  heap  or  cone  is  6  inches, 
and  this  must  be  equal  to  three-fourths 
of  the  depth.  The  proportion  of  the  Im- 
perial Bushel  to  the  Linlithgow  wheat 
firlot  is  as  106  to  105  nearly,  and  to  the 
barley  firlot  as  92  to  133  nearly. 

7.  Dimensions  of  the  Dry  Measures. 
"  The  diameter  shall  be  at  least  double 
the  depth,  and  the  height  of  the  cone  or 
heap  shall  be  equal  to  three-fourths  of 
the  depth." 

FRENCH   MEASURES   AND  WEIGHTS. 

8.  MUre.  The  standard  unit  of  the 
itinerary  and  other  measures  of  length  is 
the  Metre.  It  was  found  that  a  quadrant 
of  a  meridian  lying  between  the  North 
Pole  and  the  equator  measured  5,130,470 
toises,  or  10,936,578  English  yards ;  and 
the  ten-millionth  part  of  this  quantity, 
which  was  to  form  the  standard  unit, 
was  therefore  equal  to  3  pieds  11  ^&fa 
lignes,  or  1.093578  English  yards.  Upon 
this,  the  Academie  des  Sciences  devised 
the  following  nomenclature  in  the  eighth 
year  of  the  Republic  :— 

9.  The  words  deci  (tenth  of),  centi 
(hundredth  of),  milli  (thousandth  of),  be- 
ing added  to  that  expressing  the  unit, 
served  to  denominate  the  subdivisions ; 
and  the  words  deca  (ten),  hecto  (one 
hundred),  kilo  (thousand),  myria  (ten 
thousand),  expressed  the  multiple  of  the 
unit.  Thus  the  metre  contained  10  deci- 
metres; the  decimetre  10  centimetres; 
the  centimetre  10  millimetres.  The  de- 
cametre expressed  ten  metres;  the  hec- 
tometre, 100;  the  kilometre,  1000;  and 
the  myriamUre,  10,000  metres.  The 
kilometre  is  considered  as  the  minute 
of  the  new  geographical  degree,  and  is 
equivalent  to  513  toises  old  measure,  and 
to  1093  yards,  1  foot,  10  inches,  English. 

10.  Toise.  The  new  toise  was  fixed  at 
two  metres  exactly,  making  an  increase 
of  2£  per  cent  on  the  *  toise  of  Paris.' 
This  new  toise  is  divided  as  formerly  into 
6  feet,  each  foot  into  12  inches,  and  the 
inch  into  12  lines.  The  toise  is  therefore 
equal  to  2  metres,  or  6  feet,  6.42  inches 
English ;  the  toise  quarree,  to  3.7987 
square  metres,  or  3  yards,  1  foot,  84.096 
375 


inches  English ;  the  pied  quarre,  to 
0.4220  square  metres,  or  3  feet,  29.344 
inches  English. 

11.  Lieue.  The  lieue,  by  which  dis- 
tances were  reckoned  in  France,  was  not 
the  same  in  every  province;  of  the  fol- 
lowing four,  however,  the  proportions 
were  determined  : — 1,  the  lieue  de  poste, 
to  regulate  the  charges  on  travellers, 
equal  to  2000  toises,  old  measure,  or 
3898  metres,  or  4262yds.  2ft.  6in.  Eng- 
lish ;  2,  the  lieue  marine,  twenty  in  the 
degree,  adopted  by  geographers,  =  2850 
toises,  or  5554.75  metres,  or  6074yds.  2ft. 
English ;  3,  the  lieue  commune,  twenty- 
five  in  the  degree,  =  2280  toises,  or 
4443.80  metres,  or  4859yds.  4in.  English; 
and,  4,  lieue  moyenne,  =  2565  toises,  or 
5000  metres,  or  5470yds.  English. 

12.  Liquid  and  Dry  Measures.  The 
litre,  adopted  in  the  place  of  the  pinte,  is 
equal  to  1.074  pinte,  and  contains  1.761 
English  pint.  Its  form  is  cylindrical,  in 
height  double  of  its  diameter.  The  litre 
is  a  cubic  decimetre ;  the  decalitre  con- 
tains 10  cubic  decimetres;  the  decilitre, 
1-1 0th  of  a  cubic  decimetre.  The  hecto- 
litre contains  100  cubic  decimetres;  the 
kilolitre,  1  cubic  metre,  or  1000  cubic 
decimetres.  The  Tonneau  de  Bordeaux 
contains  931.318  litres,  or  1640  pints 
English. 

13.  Land  Measures.  The  unit  of  land 
measures  is  a  square,  each  side  of  which 
is  10  metres  in  length,  and  called  are. 
It  is  subdivided  into  100  parts,  called 
centiares,  each  a  square  metre.  There  is 
a  larger  measure  denominated  hectare, 
containing  100  ares,  and  answering  to  a 
square,  each  side  of  which  is  100  metres. 
Before  the  establishment  of  the  decimal 
system,  the  arpent  was  generally  used 
for  the  measurement  of  land. 

14.  Solid  Measures.  The  measure  in 
use  for  the  sale  of  timber  is  called  stere, 
and  is  a  cubic  metre;  the  decistere  is 
1-1 0th  of  a  cubic  metre. 

15.  Dry  and  heaped  Measures.  The 
boisseau  usuel,  such  as  its  dimensions  are 
now  fixed,  is  smaller  than  the  former, 
called  boisseau  de  Paris,  by  J,;  its  sub- 
divisions are  the  demi-boisseau,  and  the 
quart  de  boisseau.  The  double  boisseau 
is  equal  to  25  litres,  or  5  gallons,  2  quarts ; 
the  boisseau  to  12  litres,  50,  or  2  gallons, 
3  quarts ;  the  demi-boisseau  to  six  litres, 
25,  or  1  gallon,  3  pints ;  the  quart  de 
boisseau  to  3  litres,  12,  or  2  quarts, 
1  pint,  2  gills.  This  measure  serves  for 
the  sale  of  corn,  coals,  salt,  lime,  &c. 

16.  The  kilogramme   represents    the 


WEL 


WHE 


weight  of  a  cubic  decimetre  of  water  at  the 
temperature  of  four  degrees  above  that  of 
melting  ice.  The  millier  is  1000  kilo- 
grammes, or  the  weight  of  a  tun  of 
sea-water  ;  the  quintal  is  100  kilo- 
grammes; the  hectogramme  is  l-10th  of 
a  kilogramme,  the  decagramme  1-1 00th, 
the   gramme    l-1000ih,    the  decigramme 

1  -1 0,000th  of  a  kilogramme.  The  unit  used 
in  weighing  is  the  kilogramme.  It  has  been 
fixed  by,  and  is  equal  to,  the  specific 
weight  of  the  distilled  water  contained  in 
one    cubic    decimetre.      It    is    equal  to 

2  livres,  5  gros,  35  grains,  $fa  poids  de 
marc,  and  to  21bs.  8oz.  3dwt.  6.355  grains 
troy  weight,  and  21bs  2oz.  4  drams, 
16  grains  avoirdupois  weight.  The  kilo- 
gramme is  divided  into  two  livres;  the 
livre  is  subdivided  into  16  ounces,  the 
ounce  into  8  gros,  and  the  gros  into  72 
grains.  This  new  livre  exceeds  the  old 
one  (poids  de  marc)  by  -j2g,  so  that,  to 
reduce  kilogrammes  into  old  measure, 
we  must  multiply  by  2,  and  add  -^. 

17.  Terms  employed  in  the  \6th  cen- 
tury. The  measures  appear  in  most  cases 
to  have  reference  to  the  human  body. 
The  breadth  (not  the  length)  of  four  bar- 
leycorns make  a  digit,  or  finger-breadth ; 
four  digits  make  apalm  (measured  across 
the  middle  joints  of  the  fingers,  and  the 
24th  part  of  the  height  of  a  well-propor- 
tioned man);  four  palms  are  afoot,  or  a 
6th  of  the  height  of  a  man ;  a  foot  and  a 
a  half  is  a  cubit,  measured  from  the  elbow 
to  the  ends  of  the  extended  fingers,  the 
4th  of  the  height  of  a  man ;  ten  palms,  or 
two  feet  and  a  half  are  a  step  (gressus) ; 
two  steps,  or  five  feet,  are  apace  (passus) ; 
ten  feet  are  a  perch;  a  hundred  and 
twenty-five  paces  are  an  Italic  stadium ; 
eight  stadia,  or  a  thousand  paces,  are  an 
Italic  mile;  four  Italic  miles  are  a  Ger- 
man mile ;  and  five  Italic  miles  are  a 
Swiss  mile. 

WEISS-ERTZ.  The  name  given  by 
Werner  to  some  varieties  of  arsenical 
pyrites  or  mispickel,  which  contain  acci- 
dentally admixed  silver. 

WELDING.  A  property  of  certain 
metals,  as  platinum,  by  which  at  a  white 
heat,  an  incipient  fusion  takes  place, 
which  covers  their  surface  with  a  kind 
of  varnish,  so  that,  when  brought  into 
contact  in  this  state,  different  species  may 
be  permanently  united  by  forging. 

WELTER'S  TUBE.  A  safety-tube, 
introduced  into  a  Woolfe's  bottle,  to  pre- 
vent retrograde  pressure.  The  tube  is 
twice  curved  and  expanded  at  one  part 
into  a  bulb;  water  is  poured  into  the 
376 


tube  till  the  bulb  is  half  full ;  when  ab- 
sorption takes  place,  the  water  rises  in 
the  bulb  until  none  remains  in  the  tube, 
and  then  the  air  rushes  in ;  on  the  other 
hand,  no  gas  can  escape,  since  it  has  to 
overcome  the  pressure  of  a  high  column 
of  water  in  the  perpendicular  tube. 

WENLOCK  LIMESTONE  and 
SHALE.  A  component  part  of  the  Upper 
Silurian  Rocks,  1800  feet  in  thickness; 
it  consists  of  a  crystalline  grey  or  blue 
limestone,  abounding  in  corals,  encrinites, 
marine  mollusca,  and  crustaceous  ani- 
mals of  the  trilobite  family ;  and  a  dark- 
coloured  shale,  with  nodules  of  earthy 
limestone,  and  containing  mollusca  and 
trilobites. 

WERNERIAN  THEORY.  Werner 
supposed  that  all  the  geological  strata 
were  originally  in  solution  in  an  aqueous 
fluid,  from  which  they  were  deposited  or 
precipitated.  The  first  deposits  were  in 
crystals,  and  constituted  his  primitive 
rocks  ;  these  contain  no  fossils.  The 
deposits  he  termed  '  formations,'  and  he 
taught  that  '  the  exterior  of  the  earth 
consists  of  a  series  of  these  formations 
laid  over  each  other  in  a  certain  deter- 
minate order.' 

1.  The  next  deposits  he  called  trans- 
ition formations,  or  secondary  rocks;  the 
former  term  denoting  that  the  earth  was 
passing  into  a  fit  state  for  animals  and 
vegetables.  These  rocks  contain  fossils, 
or  alternate  with  those  which  do  so. 

2.  A  third  series  was  then  deposited, 
formed  in  great  measure  from  the  de- 
struction of  the  primitive  and  the  transi- 
tion formations,  and  containing  numerous 
fossils.  From  their  greater  approach  to 
the  horizontal  position,  Werner  termed 
them  floetz. 

WE'RNERITE.  Under  this  name, 
which  was  formerly  restricted  to  some 
varieties  of  common  and  compact  scapo- 
lite,  are  now  united  the  meionite  of  Vesu- 
vius, and  the  greater  part  of  the  scapolite 
of  Werner,  the  paranthine  and  also  the 
dipyre — substances  which  stand  in  need 
of  further  investigation  as  to  their  che- 
mical and  crystallographical  characters. 

WHEEL  AND  AXLE.  One  of  the 
mechanical  powers,  consisting  of  two 
cylinders,  having  their  axes  coincident, 
the  two  cylinders  forming  one  rigid  piece, 
or  being  cut  from  the  same  piece :  the 
larger  is  called  the  wheel,  the  smaller  the 
axle.  The  cord  by  which  the  weight  is 
suspended  is  fastened  to  the  axle  and 
coiled  round  it;  the  power  acts  some- 
times by  a  cord  coiled  round  the  wheel ; 


WHE 


WH  I 


sometimes  by  handspikes,  as  in  the 
capstan;  sometimes  by  handles,  as  in 
the  windlass. 

WHEEL-CUTTING.  A  term  applied 
to  a  particular  branch  of  practical  me- 
chanics, which  comprehends  the  modes 
of  cutting  the  teeth  in  the  wheels  used 
by  watch  and  clock-makers,  and  for  other 
mechanical  purposes. 

WHEEL,  EXCENTRIC.  An  appa- 
ratus employed  in  double-acting  steam- 
engines,  for  the  purpose  of  opening  and 
closing  the  valves  of  the  cylinder.  On 
the  shaft  or  axis  of  the  fly-wheel,  or 
of  the  paddle-wheel,  is  fixed  a  wheel 
which  revolves  with  it,  but  whose  motion 
is  excentric  to  it — that  is,  the  centre  of 
the  wheel  does  not  coincide  with  the 
centre  of  the  shaft  or  axis ;  and,  hence, 
the  centre  of  the  wheel  moves  round  the 
axis  of  the  shaft.  The  distance  of  the 
centre  of  the  wheel  from  that  of  the  shaft 
constitutes  the  amount  of  excentricity, 
and  this  amount  is  equal  to  one  half  of 
the  range  of  motion  of  the  valves  which 
are  to  be  worked  by  this  mechanism. 

WHEEL,  PADDLE.  A  wheel  placed 
at  each  extremity  of  the  shaft  of  a  marine 
steam-engine,  for  the  purpose  of  pro- 
pelling the  vessel  by  its  revolution.  It 
may  be  considered  as  a  series  of  levers, 
arranged  in  a  circle,  and  brought  suc- 
cessively into  action ;  the  fulcrum  is  ob- 
tained by  the  re-action  of  the  water  upon 
the  paddles ;  the  resistance  to  be  over- 
come is  that  of  the  water  opposed  to  the 
progress  of  the  vessel,  and  acting  on  the 
centre  of  the  wheel ;  the  power  by  which 
the  resistance  is  to  be  overcome,  is  ap- 
plied by  the  cranks  of  the  engine  upon 
the  shaft  which  connects  the  centres  of 
the  wheels. 

WHEEL,  RATCHET.  A  wheel  em- 
ployed for  preventing  motion  in  one 
direction,  while  it  permits  it  in  another. 
To  effect  this  object,  the  teeth  of  the 
wheel  are  cut  with  their  faces  inclining 
in  one  direction,  and  a  small  lever  or 
catch  is  so  placed,  as  to  enter  the  inden- 
tation and  stop  the  wheel  if  it  turn  back- 
wards, but  slides  over  the  teeth  without 
obstructing  them,  if  it  move  forward. 
Such  a  wheel  is  generally  employed  to 
prevent  a  weight  raised  by  a  machine 
from  descending,  and  to  obviate  other 
retrograde  movements. 

WHEEL,  SPUR,  CROWN,  BE- 
VELLED. These  are  designations  of 
toothed  wheels,  and  denote  the  position 
of  the  teeth  relatively  to  the  axis.  In 
the  spur  wheel,  the  teeth  are  raised  upon 
377 


the  edge  of  the  wheel,  or  are  perpen- 
dicular to  the  axis  ;  in  the  crovm  wheel, 
the  teeth  are  parallel  to  the  axis,  or  per- 
pendicular to  the  plane  of  the  wheel ;  in 
the  bevelled  wheel,  the  teeth  are  raised  on 
a  surface  inclined  to  the  plane  of  the 
wheel. 

WHEEL,  SUN  AND  PLANET.  A 
contrivance  for  converting  the  alternating 
motion  of  the  beam  of  a  steam-engine 
into  a  rotatory  motion.  In  this  appa- 
ratus a  toothed  wheel  is  fixed  upon  the 
axis  to  be  turned,  and  another  wheel, 
gearing  with  it,  is  attached  to  the  lower 
end  of  the  connecting  rod,  so  that  it  can- 
not revolve  on  its  own  axis.  The  result  of 
this  arrangement  is  that  the  second,  or 
planet-wheel,  passes  completely  round  the 
first  during  each  up  and  down  stroke  of 
the  engine,  and,  in  so  doing,  causes  the 
first,  or  sun-wheel,  to  rotate  upon  its  axis. 
This  apparatus  has  been  superseded  by 
the  crank. 

WHEEL,  UNDERSHOT.  A  water- 
wheel,  in  which  the  water  strikes  the 
float-boards  below  the  axle,  and  acts  by 
the  impulse  due  to  its  velocity.  See 
Overshot  wheel. 

WHET  SLATE.  Whetstone-slate.  A 
variety  of  slate,  occurring  in  beds  in  pri- 
mitive and  transition  clay-slate.  Very 
fine  specimens  are  brought  from  Turkey, 
under  the  name  of  hone-stones. 

WHINSTONE.  A  provincial  term 
applied  to  some  of  the  trap  rocks. 

WHIRLPOOL  OR  EDDY.  The  phe- 
nomenon which  occurs  when  two  oppo- 
site currents  of  the  ocean  meet  one  an- 
other, turn  upon  a  centre,  and  assume  a 
spiral  form.  The  most  celebrated  whirl- 
pools are  those  of  the  Euripus,  the  Cha- 
rybdis,  and  the  Maelstrom. 

WHIRLWIND.  A  spiral  or  whirling 
motion  of  the  wind,  which  occurs  when 
its  direction  is  influenced  by  the  form  of 
precipitous  mountains,  or  when  two 
winds  meet  each  other  at  an  angle,  and 
then  turn  upon  a  centre.  In  the  deserts 
of  Africa,  they  sometimes  draw  up  the 
sand  into  a  moving  pillar,  which  buries 
all  in  its  way.  When  they  occur  on  the 
ocean,  they  draw  up  the  water,  and  pro- 
duce water-spouts.    . 

WHISPERING  GALLERY.  A  dome 
or  room  so  constructed  that  words  uttered 
in  a  low  tone  at  one  spot  are  audible  at 
some  other  spot,  while  persons  standing 
between  these  two  points  cannot  hear 
what  is  said.  To  produce  this  effect,  the 
room  should  have  an  oval  or  elliptical 
form,  so  that  words  spoken  in  one  focus 


WI  c 

may  be  heard  in  the  other.  The  obser- 
vatory at  Paris  contains  an  apartment  of 
this  kind. 

WHITE  COPPER.  Chinese  Copper. 
A  white  metallic  compound  brought  from 
China;  its  composition  is  not  generally 
known,  but  some  of  it  is  said  to  consist 
of  copper  and  arsenic. 

WHITE  LEAD.  Ceruse.  Carbonate 
of  lead,  occurring  in  nature  well  crystal- 
lized, in  the  form  of  carbonate  of  barytes. 
It  is  employed  by  painters,  as  a  white 
pigment,  to  give  body  to  their  co- 
lours. 

WHITE  PRECIPITATE.  A  com- 
pound formed  when  ammonia  is  added 
to  a  solution  of  chloride  of  mercury.  It 
is  free  from  oxygen,  and  contains  nothing 
but  the  elements  of  a  double  chloride  and 
amide  of  mercury. 

WHITESTONE.  Eurite.  A  variety 
of  granite,  in  which  felspar  is  the  chief 
ingredient,  the  quartz,  and  especially  the 
mica,  being  very  rare ;  or  in  which  all 
the  ingredients  are  blended  into  a  finely 
granular  mass  of  a  white  appearance. 
Crystals  of  quartz  are  sometimes  dis- 
persed through  the  mass,  rendering  it 
porphyritic. 

WHORL.  In  Malacology,  this  word 
denotes  each  complete  turn  of  the  spire 
of  a  spiral  shell ;  the  last,  which  termi- 
nates the  aperture,  is  the  body  or  basal 
whorl;  the  rest  are  the  spiral  whorls. 
For  the  use  of  this  term  in  botany,  see 
Verticillus. 

WHY  ?  As  an  interrogative,  this  word 
is  employed  in  three  senses:  viz.  "By 
what  proof?"  (or  reason.)  "  From  what 
cause?"  "For  what  purpose?"  This 
last  is  commonly  called  the  "final 
cause."  E.  g.  u  Why  is  this  prisoner 
guilty  of  the  crime?"  "Why  does  a 
stone  fall  to  the  earth  ? "  "  Why  did  you 
go  to  London?"  Much  confusion  has 
arisen  from  not  distinguishing  these 
different  inquiries.     Whately. 

WICKLESS  LAMP.  This  ingeniously 
contrived  lamp  is,  as  it  is  commonly 
called,  a  self-generating  gas  apparatus. 
It  iserves  to  manufacture  oil-gas  without 
the  inconvenience  of  a  retort  and  fur- 
nace. In  its  common  form  this  lamp  con- 
sists of  fc  light  and  buoyant  dish,  which 
is  intended  to  support  the  small  tube 
through  which  the  oil  is  intended  to  be 
raised ;  this  is  effected,  partly  by  capil- 
lary attraction,  and  partly  by  hydrostatic 
pressure.  On  applying  a  taper  to  the 
tube,  the  oil  is  decomposed  at  the  ex- 
tremity, and  gas  is  generated. 
378 


WIN 

WI'LLEMITE.  A  variety  of  silicate 
of  zinc,  from  Aix-la-Chapelle. 

WINCH  AND  AXLE.  A  well-known 
apparatus,  constituting  a  small  windlass, 
and  employed  in  its  simplest  form  to 
raise  water  from  a  well,  or  solid  mate- 
rials from  the  shaft  of  a  mine  ;  in  a  more 
complex  form,  it  is  connected  with  a 
crane  for  the  purpose  of  raising  heavy 
packages  from  the  ground  to  the  upper 
part  of  a  building.  Its  mechanical  power 
is  precisely  that  of  the  wheel  and  axle. 

WIND.  A  current  in  the  atmosphere, 
occasioned  by  inequality  of  temperature 
of  the  atmosphere  at  different  points  of 
the  earth's  surface,  or  in  different  regions 
of  the  atmosphere  of  equal  eievanon. 
Permanent  winds  are  those  which  blow 
constantly  between,  and  a  few  degrees 
beyond,  the  tropics  (See  Trade  Winds). 
Those  which  blow  at  certain  periods,  as 
the  monsoons,  the  land  and  sea-breezes, 
&c,  are  called  periodical  winds. 

1.  Etesian  Winds.  A  term  formerly 
applied  to  those  winds  which  blow  every 
summer  during  six  weeks  over  the  coun- 
tries bordering  the  Mediterranean,  but 
now  applied  to  other  periodical  winds,  as 
those  which  blow  on  the  coast  of  Holland. 

2.  Helm  Wind.  A  violent  wind  which 
occasionally  prevails  between  Brampton 
in  Cumberland  and  Brough  in  West- 
moreland, a  distance  of  40  miles.  Its 
presence  is  indicated  by  a  belt  of  clouds, 
denominated  the  helm  bar,  which  re- 
mains immoveable  during  twenty-four 
or  even  thirty  six  hours,  collecting  or 
attracting  to  itself  all  the  light  clouds 
which  approach  it.  So  long  as  this  bar 
continues  unbroken,  the  wind  blows  with 
unceasing  fury,  not  in  gusts,  like  other 
storms,  but  with  continued  pressure. 

WIND-GAGE.  An  instrument  for 
measuring  the  force  or  velocity  of  the 
wind.  Various  contrivances  for  this 
purpose  have  been  employed.  One  of 
these  is  described  under  the  term  Ane- 
mometer. 

WIND-GUN.  This  is  a  more  formid- 
able instrument  than  the  air-gun.  It 
contains  a  magazine  of  bullets  as  well  as 
another  of  air,  and  when  it  is  properly 
charged,  the  bullets  may  be  projected 
one  after  another  as  fast  as  the  gun  can 
be  cocked  and  the  pan  opened.  The 
syringe  is  fixed  to  the  butt  of  the  gun,  by 
means  of  which  it  is  easily  charged,  and 
may  be  kept  in  that  state  for  a  long  time. 

WINDLASS.  A  modification  of  the 
wheel  and  axle,  consisting  of  a  barrel 
which  turns  upon  two  points  of  support 


X  AN 


XAN 


on  a  pivot  at  each  extremity  of  its  axis, 
or  upon  a  pivot  at  one  extremity  only. 
The  winch  or  crank,  by  which  the  barrel 
is  turned,  is  moved  round  by  the  hand, 
and  there  is  no  difference  in  the  principle 
whether  a  whole  wheel  is  turned,  or  a 
single  spoke.  The  winch,  therefore,  an- 
swers to  the  wheel,  while  the  rope  is 
taken  up,  and  the  weight  raised  by  the 
axle. 

WINE.  The  name  given  by  chemists 
to  all  liquors  which  have  become  spiritu- 
ous by  fermentation. 

WINE  TEST.  A  reagent  for  detect- 
ing the  presence  of  lead  in  wine,  by  con- 
verting the  acid  into  a  salt  of  lead.  That 
which  is  usually  sold  is  made  by  dis- 
solving half  an  ounce  of  sulphuret  of 
arsenic,  and  one  ounce  of  lime,  in  half  a 
pint  of  distilled  water,  and  filtering  the 
solution. 

WINTERACEjE.  The  Winter's  Bark 
tribe  of  Dicotyledonous  plants.  Trees  or 
shrubs,  with  leaves  alternate;  flowers 
hermaphrodite  or  unisexual ;  stamens 
hypogynous ;  fruit  consisting  of  a  single 
row  of  carpella. 

WI'THAMITE.  A  mineral  found  at 
Glencoe  in  Scotland,  and  regarded  as  a 
variety  of  epidote. 

WI'THERITE.  Carbonate  of  baryta, 
or  rhomboidal  baryta,  found  in  Cumber- 
land and  Durham  in  lead  veins  traversing 
a  secondary  limestone,  which  rests  on 
red  sandstone. 

WOLFRAM.  Tungstate  of  iron  and 
manganese,  occurring,  massive  and  crys- 
tallized, in  Bohemia  and  other  countries ; 
also  in  the  form  of  octohedral  supposi- 
titious crystals,  derived  from  tungstate  of 
lime. 

WO'LKONSKOIT.  An  emerald-green 
mineral,  containing  oxide  of  chromium, 
iron,  silica,  and  magnesia,  and  found  at 
Perm  in  Russia. 

WO'LLASTONITE.  Table  spar;  a 
silicate  of  lime,  found  at  Mount  Vesu- 
vius, at  Nagyag,  &c. 

WO'LNYNE.  A  variety  of  sulphate 
of  baryta  found  at  Muzsay  in  Hungary.     | 


WOOD,  ROCK.  Mountain  wood.  A 
variety  of  asbestus,  usually  massive,  of  a 
brown  colour,  and  having  the  aspect  of 
wood. 

WOOD-OPAL.  Opalized  wood;  one 
of  the  varieties  of  opal,  occurring  in  vari- 
ous vegetable  forms. 

WOOD-STONE.  The  name  given  by 
Werner  to  specimens  of  wood  which  have 
been  converted  into  hornstone,  a  silice- 
ous substance  sometimes  approaching  to 
flint  or  common  quartz. 

WOOD-TIN.  The  name  given  by 
Werner  to  one  of  his  divisions  of  oxide  of 
tin  or  tin-stone ;  a  variety  of  which,  com- 
posed of  radiated-fibrous  small  globules, 
and  marked  with  concentrically-disposed 
brown  and  yellow  colours,  is  called  toad's 
eye  wood-tin. 

WOODY  TISSUE.  Pleurenchyma. 
Elongated  cells,  tapering  to  each  end, 
and  constituting  the  elementary  struc- 
ture of  wood. 

WOORALY.  A  celebrated  poison, 
also  called  woorari,  ourari,  or  urari,  pro- 
duced by  the  Strychnos  toxifera  of 
Guayana. 

WOOTZ.  Indian  steel;  supposed  to 
be  an  alloy  of  steel  with  small  quantities 
of  silicium  and  aluminum. 

WOULFE'S  APPARATUS.  A  series 
of  two  or  three-necked  bottles,  connected 
together  by  intermediate  tubes,  used  for 
impregnating  water  with  carbonic  and 
other  gases. 

WREDE'S  EXPERIMENT.  An  ex- 
periment instituted  by  Von  Wrede  for 
measuring  the  velocity  with  which  heat 
is  propagated.  By  means  of  a  thermo- 
electric calorimeter,  placed  in  a  telescope, 
it  was  found  that  the  temperature  of  the 
eastern  edge  of  the  sun's  image  exceeded 
that  of  the  western  edge,  and  conse- 
quently the  velocity  of  the  rays  of  heat 
was  less  than  that  of  the  luminous  rays. 
The  rate  of  the  velocity  of  heat  radiated 
from  the  sun  is  only  |ths  the  velocity 
of  light,  or  about  163,600  miles  in  a 
second. 


Biporofi 


x 


XANTHIC  AND  CYANIC  SERIES. 
Botanists  have  divided  flowers  into  two 
great  series,  with  reference  to  their  co- 
lours, viz.  those  having  yellow  for  their 
type,  and  which  are  capable  of  passing 
379 


into  red  or  white,  but  never  into  blue; 
and  those  of  which  blue  is  the  type, 
which  can  pass  into  red  or  white,  but 
never  into  yellow.  The  former  series  is 
termed,  by  some  writers,  oxidised,  and 


YEA 


'YEA 


the  latter  disoxidised ;  and  greenness  is 
considered  as  a  state  of  equilibrium  be- 
tween the  two  series.  De  Can dolle  called 
the  first  series  xanthic  (fav#6s,  yellow), 
and  the  second  cyanic  {nvavos,  blue).  The 
two  series  may  be  thus  expressed : — 
Green. 


.  fa. 

I     Bl 


»l 


Greenish-blue 

Blue 

Violet-blue 

Violet 

Violet-red 


Red. 


XANTHIC  ACID  (Sav06?,  yellow). 
An  acid  composed  of  sulphur,  carbon, 
hydrogen,  and  oxygen,  and  named  from 
the  yellow  colour  of  its  compounds. 

XANTHIC  OXIDE  ($avd6t,  yellow). 
A  species  of  calculus,  named  from  the 
lemon-coloured  compound  which  it  forms 
by  the  action  of  nitric  acid. 

XANTHITE.  A  congeries  of  yellow 
grains,  no  larger  than  those  of  sand, 
easily  separable  from  one  another;  found 
in  a  limestone  bed  at  Amity  in  the  United 
States. 

XA'NTHOGEN  (Sav96?,  yellow,  yev- 
vaa>,  to  produce).  A  term  applied  to  a 
compound  of  sulphur  and  carbon,  form- 
ing the  radical  of  hydroxanthic  acid, 
from  its  property  of  forming  yellow  com- 
pounds with  certain  metals. 

XA'NTHOPHYLL  (fav06c,  yellow, 
<pu\\ov,  a  leaf).  Anthoxantine.  The 
yellow  colouring  matter  which  appears  in 
the  leaves  of  plants  in  autumn.  See 
Chlorophyll. 

XANTHOPROTEIC  ACID.  An 
orange-yellow  powder,  formed  when  al- 
bumen, or  any  other  protein-compound 
is  digested  in  nitric  acid. 

XA'NTHOUS  {Savdos,  yellow).  A  term 
applied  by  Dr.  Prichard  to  one  of  the 


three  varieties  of  mankind,  derived  from 
the  colour  of  the  hair,  and  including  all 
individuals  or  races  which  have  brown, 
auburn,  yellow,  flaxen,  or  red  hair. 

Xl'PHIAS  DORA'DO.  The  Sword 
Fish  ;  a  modern  southern  constellation, 
consisting  of  seven  stars. 

XIPHOSU'RA  ($i<pos,  a  sword,  ovpa,  a 
tail).  A  division  of  the  entomostracous 
crustaceans,  in  which  the  last  segment  of 
the  body  forms  a  long,  three-edged,  sharp- 
pointed  weapon,  as  in  the  limulus  or 
Molucca  crab. 

XI'PHYRRHYNCHS  (#0o*,  a  sword, 
pvyxos,  a  beak).  The  designation  of  a 
family  of  acanthopterygious  fishes,  of 
which  the  xiphias,  or  sword-fish,  is  the 
type. 

XY'LITE  (fyXov,  wood).  Lignone.  A 
liquid  existing  in  commercial  pyroxylic 
spirit.  There  are  several  other  products 
of  the  distillation  of  wood,  named  xylitic 
acid,  xylite-resin,  xylite-naphtha,  xylite- 
oil,  &c. 

XYLO'DIUM.  A  term  applied  by 
Desvaux  to  the  nut  of  Anacardium. 
This  fruit  is,  however,  generally  referred 
to  the  achcenium  of  other  writers. 

XYLOIDINE.  The  name  given  to 
paper  which  has  been  immersed  for  a 
moment  in  strong  nitric  acid,  and  then 
washed  in  distilled  water.  The  paper 
acquires  the  toughness  of  parchment  and 
the  combustibility  of  tinder. 

XYLOTHAGI  (fuAoi/,  wood,  <pdya>,  to 
eat).  Wood-eaters ;  a  family  of  the  tetra- 
merous  Coleoptera,  which  usually  live  on 
wood,  which  their  larvae  penetrate  in 
every  direction.  By  the  term  xylotroges 
(Tpa»7&>,  to  gnaw)  is  denoted  a  tribe  of 
serricorn  beetles,  which  perforate  timber ; 
and  by  that  of  xylophilans  (<pt\4ia,  to  love) 
a  tribe  of  beetles  which  live  on  decayed 
wood. 


YA'NOLITE.  A  designation  of  the 
axinite  of  Haiiy,  and  thumerstone  of 
Kirwan ;  an  alumino-silicate  of  lime  and 
iron. 

YEAR.  The  period  of  time  in  which 
the  earth  performs  her  revolution  round 
the  sun,  or  that  in  which  the  sun  appa- 
rently moves  from  a  point  in  the  ecliptic 
until  he  returns  to  the  same  point,  is 
called  the  solar  year.  This  is  also  termed 
the  tropical  year,  and  it  consists  of  365d. 
380 


5h.  48m.  49s.  7.  This  is  the  period 
adopted  as  the  standard  for  the  measure- 
ment of  time,  for  all  the  purposes  of  civil 
life;  hence,  it  is  also  called  the  civil 
year. 

1.  The  sidereal  year  is  measured  from 
the  departure  of  the  sun  from  any  fixed 
star  to  his  return  to  the  same  star ;  it  is 
longer  than  the  tropical  year,  consisting 
of  365d.  6h.  9m.  9s.  6,  reckoned  in  mean 
solar  time,  or  366d.  6h.  9m.  9s.  6  reckoned 


ZAM 


ZE  A 


in  sidereal  time.  The  reason  of  this  dif- 
ference is,  that,  as  the  sun's  apparent 
annual  motion  among  the  stars  is  per- 
formed in  a  contrary  direction  to  the 
apparent  diurnal  motion  of  hoth  sun  and 
stars,  it  comes  to  the  same  thing  as  if  the 
diurnal  motion  of  the  sun  were  so  much 
slower  than  that  of  the  stars,  or  as  if  the 
sun  lagged  behind  them  in  its  daily 
course.  When  this  has  gone  on  for  a 
whole  year,  the  sun  will  have  fallen  be- 
hind the  stars  by  a  whole  circumference 
of  the  heavens ;  or,  in  other  words,  in  a 
year,  the  sun  will  have  made  fewer  diur- 
nal revolutions  by  one  than  the  stars. 
The  proportion  between  the  mean  solar 
and  the  sidereal  day  is,  when  reduced  to 
a  decimal  fraction,  that  of  1.00273791  to  1. 

2.  The  anomalistic  year  is  the  time 
which  elapses  between  the  sun's  leaving 
his  apogee  and  his  return  to  it,  consisting 
of  365d.  6h.  13m.  49s.  3.  The  difference 
between  this  and  the  tropical  or  civil 
year  is  owing  to  the  orbit  of  the  earth 
representing  an  ellipse,  of  which  the 
major  axis  has  a  slow  motion  of  11".8  per 
annum  in  advance. 

3.  Historical  and  ecclesiastical  year. 
In  England,  the  historical  year  was,  for 
a  very  long  period,  begun  on  the  1st  of 
January.  But  the  civil,  ecclesiastical, 
and  legal  year  began,  until  the  end  of  the 
thirteenth  century,  at  Christmas.  In  and 
after  the  fourteenth  century,  it  com- 
menced on  the  25th  of  March,  and  so 
continued  until  the  1st  of  January,  1753. 
Much  confusion  arose  from  these  two 
modes  of  computing  dates  ;  for  the  legis- 
lature, the  ecclesiastics,  and  the  civilians, 
referred  every  event  which  happened  be- 
tween the  1st  of  January  and  the  25th  of 
March  to  a  different  year  from  historians. 

4.  To  avoid,  so  far  as  possible,  the  mis- 
takes which  this  custom  produced,  it  was 
usual  to  add  the  date  of  the  historical  to 
that  of  the  legal  year,  when  speaking  of 


any  day  between  the  1st  of  January  and 
the  25th  of  March ;  thus,— 

8  fi.e.  the  civil  and  legal 
Jan.  30,  164     -j     year, 

9  \i.  e.  the  historical  year  ; 
or,  thus : 

January  30,  1648-9. 

YEAST.  Fermentum.  A  substance 
generated  during  the  vinous  fermenta- 
tion of  vegetable  juices  and  decoctions, 
rising  to  the  surface  in  the  form  of  a 
frothy,  flocculent,  and  somewhat  viscid 
matter.  It  is  used  for  promoting  fer- 
mentation.    See  Catalysis. 

■Artificial  Yeast  may  be  made  by  boil- 
ing malt,  pouring  off  the  water,  and 
keeping  the  grains  in  a  warm  place  to 
ferment,  repeating  the  process  till  a  suf- 
ficient quantity  is  procured. 

YELLOW  EARTH.  A  massive  mine- 
ral of  an  ochre-yellow  colour,  consisting 
of  silica,  alumina,  iron,  and  lime.  It 
occurs  in  Upper  Lusatia,  associated  with 
clay  and  clay-ironstone.  When  burnt, 
it  is  sold  by  the  Dutch  as  a  pigment, 
under  the  name  of  English  red. 

YENITE.  Another  name  for  lievrite, 
a  double  silicate  of  lime  and  iron,  found 
in  the  Isle  of  Elba  and  in  Norway.  It 
was  named  yenite  by  Lelievre,  its  disco- 
verer, in  honour  of  the  battle  of  Jena. 

YOU-STONE.  Chinese  jade;  a  zeo- 
litic  substance  referred  to  prehnite. 

YTTRIA.  A  new  earth,  dis  overedby 
Gadolin,  in  a  mineral  from  Yiterby  in 
Sweden.  Its  metallic  base  is  yttrium,  of 
which  it  is  considered  to  be  a  protoxide. 

YTTRO-CERITE.  A  mineral  sub- 
stance containing  yttria,  oxide  of  cerium, 
and  fluoric  acid  ;  it  is  found  at  Finbo  in 
Sweden,  imbedded  in  quartz,  or  incrust- 
ing  pyrophysalite. 

YTTRO-TANTALITE.  An  ore  of 
tantalum,  also  called  yttrious  oxide  of 
tantalum,  found  in  reniform  masses  at 
Ytterby  in  Sweden. 


ZAFFRE.  An  impure  oxide  of  cobalt, 
being  the  residuum  of  the  native  arseni- 
uret  of  cobalt,  after  the  sulphur,  arsenic, 
and  other  volatile  matters  of  this  mineral 
have  been  expelled  by  calcination.  The 
substance  brought  from  Saxony,  and 
commonly  sold  under  this  name,  is  a 
mixture  of  oxide  of  cobalt  with  vitrifiable 
earth. 

Z  AMITE.  The  name  given  to  the 
fossil  species  of  zamia,  the  principal 
381 


forms  of  which  have  been  found  in  the 
lias  and  oolitic  formations.  They  differ 
from  the  other  species  in  the  exsertion 
and  venation  of  their  leaves. 

ZANTHOPI'CRITE.  A  crystalline 
substance  extracted  from  the  bark  of  the 
zanthoxylum  of  the  Caribbee  islands. 

ZEA'GONITE.  A  Vesuvian  mineral 
referred  to  the  harmotone  or  cross-stone, 
and  to  the  potass  division  of  this  zeolitic 
substance. 


ZER 


ZI  N 


15^^ 


ZE'CHSTEIN.  A  magnesian  of  lime- 
stone, abounding  in  Germany,  and  be- 
longing to  the  New  Red  Sandstone 
group. 

ZE'IN.  A  substance  procured  from 
the  zea  mays,  resembling  gluten,  but  said 
to  be  destitute  of  nitrogen. 

ZENITH  AND  NADIR.  These  are 
astronomical  terms  derived  from  the 
Arabic,  and  they  denote  two  points  of  the 
sphere  of  the  heavens,  the  former  verti- 
cally over  a  spectator's  head,  the  latter 
vertically  under  his  feet ;  they  are,  there- 
fore, the  vanishing  points  of  all  lines 
mathematically  parallel  to  the  direction 
of  a  plumb-line  at  his  station.  They  are 
the  poles  of  the  celestial  horizon,  t.  e. 
points  90°  distant  from  every  point  in  it. 

ZENITH  DISTANCE.  An  astrono- 
mical term,  denoting  the  complement  of 
the  altitude  of  the  sun,  or  other  heavenly 
body.  Vertical  circles  of  the  sphere  are 
great  circles  passing  through  the  zenith 
and  the  nadir,  or  great  circles  perpen- 
dicular to  the  horizon ;  on  these  are 
measured  the  altitudes  of  objects  above 
the  horizon — the  complements  to  which 
are  their  zenith  distances. 

ZENITH  SECTOR.  An  astronomical 
instrument,  consisting  of  a  portion  of  a 
divided  circle,  employed  for  measuring 
accurately  the  zenith  distances  of  stars 
which  pass  near  the  zenith.  This  instru- 
ment is  also  used  in  trigonometrical  sur- 
veys for  determining  the  difference  of 
latitude  of  two  stations ;  for  the  differ- 
ence of  the  zenith  distances  of  the  same 
star,  observed  at  its  meridional  passages 
at  two  places,  gives  the  difference  of  the 
astronomical  latitudes  of  the  places  with- 
out any  regard  to  the  star's  declination. 

ZE'OLITES  (£?«,  to  boil,  \i0os,  a 
stone).  A  term  applied  to  the  silicates 
of  lime  and  alumina,  from  their  frothing, 
when  heated  before  the  blow-pipe.  This 
is  a  very  extensive  mineral  genus,  con- 
taining the  dodecahedral  species,  or  leu- 
cite;  the  hexahedral,  or  analcime;  the 
rhomboidal,  or  chabasite;  the  pyramidal, 
or  cross-stone;  the  diprismatic,  or  lau- 
monite;  the  prismatic,  or  mesotype,  com- 
prising the  fibrous  zeolite,  natrolite,  and 
mealy  zeolite ;  the  prismatoidal,  or  stil- 
bite,  comprehending  foliated  and  radiated 
zeolite  ;  and  the  axifrangible,  or  apo- 
phyllite. 

ZE'RO  {tsaphara,  Arab.,  empty).  A 
term  used  to  denote  a  cipher  placed  be- 
tween the  ascending  and  the  descending 
numbers  of  a  scale  or  series.  The  zero 
of  Fahrenheit's  thermometer  is  32°  below 
382 


the  melting  point  of  ice;  that  of  the  cen- 
tigrade scale  coincides  with  the  freezing 
point  of  water.  The  absolute  zero  is  the 
imaginary  point  in  the  scale  of  tempera- 
ture at  which  the  whole  heat  is  ex- 
hausted ;  it  is  the  expression  of  absolute 
cold,  or  privation  of  caloric. 

ZERO  POINT.  The  term  applied  by 
astronomers  to  that  point  of  the  equi- 
noctial, called  the  equinox,  through  which 
they  suppose  the  hour  circle  to  pass,  from 
which  all  others  are  reckoned,  and  which 
point  is  itself  the  zero  point  of  all  right 
ascensions  counted  on  the  equinoctial. 

ZETE'TICS  (Cnreia,  to  search).  The 
name  given  by  Vieta  to  the  department 
of  algebra  which  consists  in  the  direct 
search  after  unknown  quantities.  The 
term  is  now  obsolete. 

ZEUXITE.  A  zeolitic  substance,  found 
in  Huel-Unity  Mine,  near  Redruth,  in 
Cornwall. 

ZINC.  A  bluish-white  metal,  occur- 
ring in  the  form  of  oxide,  or  red  zinc; 
of  sulphuret,  or  blende;  of  carbonate,  or 
calamine;  of  sulphate,  or  white  or  zinc 
vitriol;  of  silicate,  or  electric  calamine; 
and  ofaluminate,  or  automalite  or  gahnite. 
It  has  been  called  marcasite,  Indian  tin, 
and  spelter.  When  rolled  into  thin  leaves, 
it  is  termed  sheet  zinc.  The  mineral  sub- 
stance, zinc  bloom,  is  of  the  same  com- 
position as  calamine,  or  the  carbonate  of 
this  metal. 

1.  Zinc,  floivers  of.  This  is  the  oxide, 
formed  by  exposing  the  metal  to  the  air 
at  a  temperature  a  little  above  its  melting 
point,  when  it  flies  up  in  the  form  of 
white  flowers.  It  has  hence  received  the 
fanciful  names  of  nihil  album  and  philo- 
sophical wool.  By  the  ancients  it  was 
called  pompholix.  In  Holland  it  was 
sold  as  a  secret  remedy  under  the 
names  of  luna  fixata  and  arcanum  Lude- 
manni. 

2.  Zinc,  butter  of.  This  is  the  chloride 
or  hydrochlorate,  obtained  as  a  whitish- 
grey  mass,  with  the  consistency  of  wax 
or  butter. 

ZINCOID  AND  CHLOROID.  These 
terms  are  applied,  on  the  electrical  hypo- 
thesis, to  the  plates  of  a  decomposing 
cell :  the  chlorous  plate,  which  is  in  con- 
nection with  a  zinc  plate,  is  termed  the 
chloroid  (like  chlorine,  quasi-chlorine), 
and  is  the  same  as  the  negative  pole,  the 
negative  electrode,  the  cathode  and  the 
platinode  ;  while  the  zincous  plate,  which 
is  connected  with  a  copper  plate,  is  called 
the  zincoid  (like  zinc,  quasi-zinc),  and 
represents  the  positive  pole,  the  positive 


ZO  A 


ZOO 


electrode,  the  anode,  and  the  zincode. 
See  Polarity,  Chemical. 

ZINCO'LYSIS.  A  term  equivalent  to 
electrolysis,  denoting  a  mode  of  decom- 
position occasioned  by  the  inductive  ac- 
tion of  the  affinities  of  zinc  or  the  positive 
metal. 

ZI'NCOLYTE.  A  term  equivalent  to 
electrolyte,  denoting  a  body  decomposible 
by  electricity,  the  decomposition  being 
referred  to  the  action  of  zinc  or  the  posi- 
tive metal. 

ZINCOUS  ELEMENT.  The  basic  or 
positive  element  of  a  binary  compound. 
The  negative  is  termed  the  chlorous  ele- 
ment. 

ZINCOUS  POLE.  A  term  founded 
on  the  theory  that  the  particles  of  matter 
are  susceptible  of  polarity.  Hence  that 
pole  of  a  particle  of  zinc  or  of  hydrochloric 
acid  which  has  the  attraction,  or  affinity, 
which  is  characteristic  of  zinc,  or  zincous 
attraction,  is  called  the  zincous  pole.  See 
Chlorous  Pole. 

ZINGIBERA'CE^E.  Scitamineee.  The 
Ginger  tribe  of  monocotyledonous  plants. 
Aromatic  tropical  herbaceous  plants,  with 
a  creeping  rhizome,  and  stem  formed  of 
the  cohering  bases  of  the  leaves ;  inflo- 
rescence either  a  dense  spike,  or  a  ra- 
ceme, or  a  sort  of  panicle,  terminal  or 
radical.  The  family  are  monandrous, 
with  a  whole  anther,  and  are  thus  distin- 
guished from  the  allied  family  maran- 
tacecc,  which  are  monandrous,  with  only 
half  an  anther ;  and  from  the  musacece, 
which  have  five  or  six  anthers. 

ZI'NKENITE.  A  mineral  containing 
sulphur,  lead,  antimony,  and  copper.  It 
is  nearly  related  to  plumose  antimony. 

ZIRCON.  A  heavy,  hard,  sparkling, 
and  transparent  stone,  having  a  strong 
double  refraction.  It  is  usually  divided 
into  the  two  varieties  of  hyacinth  and 
jargon,  the  former  having  a  yellowish-red 
colour,  and  the  latter  being  most  esteemed 
when  colourless. 

ZIRCO'NIA.  The  oxide  of  zirconium; 
a  peculiar  earth,  discovered  in  the  zircon 
of  Ceylon,  a  silicate  of  zirconia,  which 
is  also  found  in  the  syenitic  mountains  of 
the  south-east  side  of  Norway.  The 
hyacinth  is  the  same  mineral  of  a  red 
colour. 

ZIRCO'NIUM.  The  metallic  basis  of 
zirconia,  obtained  in  the  form  of  a  black 
powder,  resembling  that  of  charcoal. 

ZOANTHA'RIA    (£Sov,     an    animal, 
av6ot,  a  flower).      Animal-flowers  ;   the 
third  class  of  zoophytes,  in  the  arrange- 
ment of  De  Blainville,  who  gives  the  fol- 
383 


lowing  definition  :  —  "  Body  regular, 
flower-shaped,  more  or  less  elongated, 
free  or  fixed,  very  contractile,  furnished 
with  an  intestinal  canal  (?),  without  dis- 
tinct walls,  having  a  single  large  terminal 
opening  surrounded  by  variously-shaped 
tentacula,  which  are  always  tubular  and 
in  communication  with  the  musculo- 
cavernous  parenchyma  of  the  skin." 

ZOA'NTHID^E.  A  family  of  the 
zoantharia  of  De  Blainville,  comprising 
animals  coriaceous,  simple,  or  compound, 
fixed;  tentacula  marginal,  surrounding 
the  mouth. 

ZO'DIAC  {&diov,  a  little  animal).  The 
area  within  which  the  apparent  motions 
of  the  sun,  moon,  and  all  the  greater 
planets  are  confined.  It  consists  of  a  zone, 
or  belt,  extending  nine  degrees  on  either 
side  of  the  ecliptic,  and  named  from  its 
containing  the  figures  of  all  the  animals, 
&c,  which  formed  the  twelve  signs.  The 
names  of  the  signs  are  derived  from  com- 
parisons made  by  the  Egyptians  between 
celestial  and  terrestrial  phenomena,  for 
the  most  part  purely  of  a  local  nature, 
and  belonging  exclusively  to  a  part  of 
their  country.     See  Signs  of  the  Zodiac. 

ZODI'ACAL  LIGHT.  A  term  applied 
by  astronomers  to  a  revolving  ring  of 
finely-divided  or  nebulous  matter,  situ- 
ated perhaps  between  the  orbits  of  Venus 
and  Mars,  but  certainly  extending  beyond 
that  of  the  earth.  This  phenomenon 
rising  pyramidally  illumines  a  portion  of 
the  unvarying  length  of  the  tropical 
nights.  In  the  temperate  zone,  it  is  only 
distinctly  visible  in  the  beginning  of 
spring,  when  it  may  be  seen  after  even- 
ing twilight  above  the  Western  horizon, 
and  at  the  end  of  Autumn,  before  the 
commencement  of  morning  twilight  above 
the  Eastern  horizon. 

ZO'ISITE.  A  subspecies  of  prisma- 
toidal  augite,  distinguished  into  the  com- 
mon and  the  friable.  It  was  named  after 
its  discoverer,  the  Baron  Von  Zois. 

ZONE  {zona,  a  girdle).  The  geogra- 
phical denomination  of  each  of  the  five 
parallel  belts  into  which  the  earth  is 
imagined  to  be  divided  in  respect  to  tem- 
perature. The  torrid  zone  includes  all 
the  space  which  lies  between  the  tropics, 
being  nearly  47  degrees,  or  23£  degrees 
on  each  side  of  the  equinoctial  line.  Two 
frigid  zones  occupy  those  parts  which  lie 
between  the  poles  and  the  polar  circles ; 
and  two  divisions  which  lie  between  those 
circles  and  the  torrid  zone,  are  called  the 
temperate  zones. 
ZO'OCARFES  (ffiov,  an  animal,  »cap- 


ZOOLOGY. 


7to9,  fruit).  The  name  given  to  certain 
organized  bodies  which  have  been  vari- 
ously considered  as  animals,  as  plants, 
and  as  partaking  of  the  characters  of  each 
of  these  divisions  of  organized  beings. 
They  are  found  among  the  lower  forms  of 
algce  of  botanists,  as  the  diatoma,  the 
fragillaria,  &c. 

ZOO'LOGY  (twov,  an  animal,  Xo'yo?,  a 
description).  That  branch  of  Natural 
Science  which  investigates  the  nature, 
properties,  and  classification  of  the  sub- 
jects of  the  Animal  Kingdom.  Under 
the  term  Animal  Kingdom,  a  table  is 
given  of  the  terms  employed  by  different 
writers  in  classifying  these  subjects. 

I.  Divisions  of  Aristotle.  Aristotle's 
primary  divisions  were  derived  from  the 
presence  and  the  (supposed)  absence  of 
blood  in  animals,  which  were,  therefore, 
termed  enaima  [kv,  in,  ai/xa,  blood)  or 
sanguineous,  including  beasts,  birds, 
reptiles,  and  fishes ;  and  anaima  (a,  priv. 
al/xa,  blood)  or  ex-sanguineous,  including 
all  the  lower  species.    The  subsequent 


discovery  of  white  blood  in  animals,  and 
the  substitution  of  the  terms  "  red- 
blooded  "  and  white-blooded  "  for  the  pri- 
mary divisions  of  Aristotle,  were  steps  in 
the  progress  of  improvement. 

2.  Divisions  of  Linnceus.  In  the  "Sys- 
tema  Naturae  "  the  natural  divisions  of 
the  Animal  Kingdom  are  indicated  by 
internal  structure.  Thus,  with  a  bilocular 
heart  with  two  auricles,  and  warm,  red 
blood,  we  have  viviparous  animals  in  the 
Mammalia,  oviparous  in  the  Birds.  With 
a  unilocular  heart  with  one  auricle,  and 
cold,  red  blood,  we  have,  furnished  with 
arbitrary  lungs,  the  Amphibia,  with  ex- 
ternal gills,  the  Fishes.  With  a  unilocu- 
lar heart  with  one  auricle,  and  cold, 
white  circulating  fluid  (sanies),  we  have, 
furnished  with  antennae,  the  Insects,  with 
tentacula,  the  Worms. 

3.  Divisions  of  Cuvier.  The  following 
table  exhibits  Cuvier's  fourfold  division 
of  the  Animal  Kingdom,  together  with 
the  classes,  sub-classes,  orders,  and  an 
example  of  each  division : — 


Div.  I.— VERTEBRATA. 


Animals  which  have  an  internal  skeleton,  supported  by  a  spine. 


Class, 


I.  Mammalia 

Animals  which  suckle  their 
young. 


II.  Aves  .... 
Birds. 


III.  Reptilia    , 
Reptiles. 


Sub-Class. 
I.  Osseous 


IV.  Pisces  ... 

Fishes. 


Order. 

1.  Bimana. 

2.  Quadrumana. 

3.  Carnivora. 

4.  Rodentia. 

5.  Edentata. 

6.  Pachyderma. 

7.  Ruminantia. 

8.  Cetacea. 

rl.  Accipitres. 

2.  Passeres. 
I  3.  Scansores. 
i  4.  Gallinae. 

5.  Grallae. 
[6.  Palmipedes. 

(1.  Chelonia. 
)  2.  Sauria. 
|  3.  Ophidia. 
1 4.  Batrachia. 

1.  Acanthopterygii. 

2.  Malacopterygii    1 
Abdominales.      J 

3.  Malacopterygii    \ 
Sub-brachiati.     j 

4.  Malacopterygii    1 
Apodes.  J 

5.  Lophobranchii. 

6.  Plectognathi. 


Cartilaginous. 
Chondropterygi 


s.  n. 

"i8: 


Sturiones. 

Selachii. 

Cyclostomi. 


Example. 

Man. 

Monkeys. 

Hyaena. 

Rabbit. 

Sloth. 

Elephant. 

Cow. 

Whale. 

Eagle. 

Sparrow. 

Parrot. 

Pheasant. 

Heron. 

Duck. 

Tortoise. 

Lizard. 

Serpent. 

Frog. 

Perch. 

Pike. 
Cod. 

Eel. 

Hippocampus. 
Sun-fish. 

Sturgeon. 

Shark. 

Lamprey. 


ZOOLOGY. 


Div.  II.— MOLLUSCA. 


Soft,  invertebral,  inarticulate  animals,  often  protected  by  a  shell. 


Class. 
I.  Cephalopoda  . 
Head-footed. 

II.  Pteropoda 

Fin-footed. 


III.  Gasteropoda    ., 
Belly-footed. 


IV.  Acephala   

Headless. 

V.  Brachiopoda 

Arm-footed. 

VI.    ClRRHOPODA    

Bristle-footed. 


Order. 

Example. 

|  (One.)  Cephalopoda. 

Cuttle-fish. 

|  (One.)  Pteropoda. 

Clio. 

p.  Pulmonibranchia. 

Snail. 

2.  Nudibranchia. 

Glaucus. 

3.  Inferobranchia. 

Diphyllidia. 

4.  Tectibrancbia. 

Bulla. 

(  5.  Heteropoda. 

Carinaria. 

6.  Ptenobranchia. 

Whelk. 

7.  Tubulibranchia. 

Vermetus. 

8.  Scutibranchia. 

Sea-ear. 

.9.  Cyclobranchia. 

Chiton. 

1 1.  Testacea. 

Oyster. 

12.  Nuda. 

Ascidia. 

J-  (One.)  Brachiopoda.      Lingula. 
\  (One.)  Cirrhopoda.        Barnacle. 


Div.  III.— ARTICULATA. 


Animals  with  bodies  covered  with  a  case  divided  into  rings. 


Annelida  * 

Ring-bodied  animals. 


a 


.  Tubicola.  Wormshell. 

Dorsibranchia.         Lobworm. 
Abranchia.  Earthworm. 


II.  Crustacea, 
Cmstacequs 
animals. 


I.  Malacostracia,( 
Crustaceous-shelled.  ' 


II.  Entomostracia, 
Thin-shelled. 


III.  Arachnida 

The  Spider-tribe. 


IV.  Insecta    ... 
Insects. 


885 


1.  Decapoda. 

Lobster. 

2.  Stomapoda. 

Sea  mantis. 

3.  Amphipoda. 

Shrimp. 

4.  Laemodipoda. 

Whale-louse 

5.  Isopoda. 

Cymothoa. 

f  6.  Branchiopoda. 

Monoculus. 

L  7.  Pcecilopoda. 

King-crab. 

/  1.  Pulmonata. 
1  2.  Trachearia. 

Tarantula. 

Mite. 

-  1.  Myriapoda. 

Centipede. 

2.  Thysanoura. 

Springtail. 

3    Parasita. 

Louse. 

4.  Suctoria. 

Flea. 

5.  Coleoptera. 

Beetle. 

6.  Orthoptera. 

Ear-wig. 

7.  Hemiptera. 

Bug. 

8.  Neuroptera. 

Ant-lion. 

9.  Hymenoptera. 

Wasp. 

10.  Lepidoptera. 

Butterfly. 

11.  Rhipiptera. 

Stylops. 

112.  Diptera. 

Fly. 

S 

ZU  M 


Z  YM 


Div.  IV.— RADIATA. 

Animals  disposed  around  an  axis. 


Class. 

I.    ECHINOBERMA   

,  Hard-skinned. 
II.  Intestina  

Intestinal  worms. 

III.  ACALEPHA    

Sea  nettles. 

IV.  Polypi  

Plant-like  animals. 

V.  Infusoria  

Water  animalcules. 


Order. 

{I.  Pedicellata. 
2.  Apoda. 
(    1.  Cavitaria. 
\  2.  Parenchyma. 
,  Simplex. 

Hydrostatica. 

1.  Carnosa. 
Gelatinosa. 
Corallicola. 
Rotifera. 

2.  Homogenea. 


(   L 

(  3. 


u 


Example. 
Star-fish. 
Sipunculus. 
Guinea-worm. 
Tapeworm. 
Medusa. 

{Spanish  man-of- 
war. 
Sea  anemone. 
Vorticella. 
Coral. 

Wheel  insect. 
Globeanimalcule. 


ZOO'NIC  ACID  (f5ov,  an  animal). 
This  is  merely  the  acetous  acid,  holding 
animal  matter  in  solution. 

ZOO'NOMY  (fwov,  an  animal,  vo^oc, 
a  law).  The  science  which  treats  of  the 
laws  of  organic  life. 

ZOO'PHAGOUS  (twov,  an  animal, 
<pdj(o,  to  eat).  Animal-eating ;  a  term 
applied  to  a  division  of  the  cetaceous 
animals,  and  to  a  tribe  of  carnivorous 
gasteropods  —  the  pectinibranchiata  of 
Cuvier.     See  Phytophagous. 

ZO'OPHYTES  (fwoi/,  an  animal,  cpOrov, 
a  plant).  Animal-plants;  a  division  of  the 
animal  kingdom,  including  the  corals, 
sponges,  and  other  aquatic  animals  allied 
to  them.  They  are  so  named,  because, 
while  they  are  the  habitation  of  animals, 
they  are  fixed  to  the  ground,  and  have  the 
forms  of  plants.  They  were  considered  by 
Cuvier  as  synonymous  with  the  radiata. 
Their  characters  are  given  under  the 
terms  Echinodermata,  Entozoa,  Aca- 
lephae,  Polypus,  and  Infusoria. 

ZUBENELY,  or  p  LIBRA.  A  star  of 
the  second  magnitude,  in  Libra. 

ZUBENESCH,  or  a  LIBRA.  A  star 
of  the  second  magnitude,  in  Libra. 

ZUBERNICH  MELI.  A  star  of  the 
second  magnitude  in  the  constellation 
Libra. 

ZUMIC  ACID  (tv^n,  leaven).  An 
acid  discovered  in  vegetable  substances 
which  have  undergone  the  acetous  fer- 
mentation. It  has  been  shown  to  re- 
semble closely  the  lactic  acid. 

ZUMO'METER  {&ixr\,  leaven,  fierpov, 
a  measure).    Zumosimeter.     An  instru- 


ment for  measuring  the  degree  to  which 
fermentation  has  proceeded  in  ferment- 
ing liquors. 

ZU'NDERERZ.  Tinder  ore;  an  ore 
of  silver,  occurring  in  the  Hartz,  in 
fibrous  flakes  resembling  Under. 

ZURLITE.  A  mineral  occurring  in 
rectangular  prisms  and  in  botryoidal 
masses,  of  an  asparagus-green  colour.  It 
occurs  on  Mount  Vesuvius  with  calcare- 
ous spar. 

ZYGODA'CTYLES  (£vyorf  a  yoke, 
ddKTvXot,  a  finger).  The  name  given  by 
Zernminck  to  an  order  of  climbing  birds, 
including  those  which  have  the  toes 
arranged  in  pairs,  two  before  and  two 
behind,  as  the  parrot,  the  woodpecker, 
the  toucan,  the  cuckoo,  &c.  They  cor- 
respond with  the  Scansores  of  Cuvier. 

ZYG^'NIDjE.  A  tribe  of  lepidopter- 
ous  insects,  named  from  the  typical 
genus  zygcena,  and  arranged  by  Linnaeus 
with  the  Sphinges  on  account  of  the 
resemblance  of  their  antennas  to  those  of 
that  family. 

ZYGOPHYLLA'CE^.  The  Bean 
Caper  tribe  of  dicotyledonous  plants. 
Trees,  shrubs,  and  herbaceous  plants, 
with  leaves  opposite;  flowers  polypetal- 
ous,  symmetrical ;  stamens  hypogynous  ; 
ovarium  many-celled  ;  fruit  capsular. 

Z Y'MOME  (#/xi>  leaven).  The  residue 
of  the  gluten  of  wheat,  after  it  has  been 
treated  by  alcohol,  and  has  parted  with 
its  gliadine  and  water.  It  produces  vari- 
ous kinds  of  fermentation,  according  to 
the  nature  of  the  substance  with  which  it 
comes  in  contact. 


Gilbert  &  Rivington,  Printers,  St.  John's  Spuare,  London. 


WORKS  BY  THE  SAME  AUTHOR. 


i. 
DICTIONARY   OF   MEDICAL  TERMS. 

Fourth  Edition. 

NOTICES   OF   THE    FIRST   EDITION. 

"  A  work  much  wanted,  and  very  ably  executed." — London  Medical  Journal, 
Sept.  1835. 

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a  complete  Glossary  of  the  terms  used  in  Medicine, — not  only  those  in  common  use, 
but  also  the  more  recent  and  less  familiar  names  introduced  by  modern  writers.  The 
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containing  much  excellent  matter  in  a  little  space,  and  is  deserving  of  our  strong 
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mation in  a  very  small  compass." — British  and  Foreign  Medical  Review. 

II. 

MANUAL   OF    NATURAL   PHILOSOPHY. 

By  COMSTOCK  AND  HOBLYN. 

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on  the  student  and  on  the  medical  practitioner.  It  equally  deserves  our  commen- 
dation as  an  important  guide  to  general  education." — Lancet,  1841. 

"Mr.  Hoblyn's  '  Manual  of  Chemistry'  is  entitled  to  general  praise,  for  the  grasp 
of  its  subject,  the  distinctness  of  its  arrangement,  the  fulness  of  its  matter,  and  the 
clearness  of  its  style,  as  well  as  for  the  force  with  which  the  points  of  the  subject 
are  frequently  impressed  upon  the  mind  by  the  selection  of  some  striking  fact." — 
Spectator,  1841. 

IV. 

A    MANUAL    OF    THE    STEAM   ENGINE. 

Illustrated  by  numerous  Engravings  on  Steel  and  Wood.    Fcap.  8vo.  6s. 

"  A.  work  which,  for  cheapness  and  compactness,  extensive  range  of  subject,  and 
competent  illustration,  we  can  safely  recommend  to  our  readers  as  the  best  of  the 
day." — Railway  Magazine,  1842. 

V. 

FIRST    BOOKS    IN    SCIENCE. 

Price  1*.  each, 

1.  ASTRONOMY. 

2.  NATURAL  PHILOSOPHY. 

3.  HEAT,  LIGHT,  and  ELECTRICITY. 

4.  CHEMISTRY. 


C  ot  tit  /^CL^c^t^  / 


